Coatings For Energy Blog | Applications for oil, gas, coal, renewables

How to Stop Refinery Metal Filter Fouling and Membrane Fouling

Posted by Marty Higgins on Jun 15, 2018 10:31:00 AM


Metal filters are critical to process and environmental quality.  Unfortunately in doing their job, filters capture particulates and eventually clog and foul.  Fouling can disrupt process fluid flow and can cause process shutdowns, here's how to reduce fouling and improve filter performance.  Oh and maybe save a lot of money!


In this blog post you will learn:

  • How silicon CVD coatings can change the surface energy, lubricity and fouling properties of a surface.
  • How coatings like Dursan and Notak can reduce filtration differential pressure.
  • How anti fouling coatings can extend the life of metal filters and prevent membrane fouling.

 How silicon coatings change the surface properties of metal filters.

Coated frit 3Coatings like Dursan and Notak™ are bonded to the surface of metal filters by a patented chemical vapor deposition process.  The coating gas penetrates the filter and creates a micro thin barrier coating throughout the filter area.  Even sintered metal frits can be treated.  The barrier coating bonds and penetrates into the surface creating a corrosion resistant, fouling resistant surface with high lubricity.  The sputter depth profile below highlights the silicon steel diffusion zone and bond to the stainless steel filter surface.  See how Dursan can solve your material problem.  

Dursan Composition-057151-edited

After processing, the filter will take on the surface properties of the coating, enhancing the corrosion resistance, fouling resistance, lubricity, surface energy/ hydrophobicity of the filter.  Read more about how our coatings prevent fouling.


Wear and Friction Data

Pin-on-disc comparison of Dursan (carboxysilane) to an oxidized stainless steel surface shows a 50% reduction in wear rate and a 35% reduction in coefficient of friction, improving the efficiency and wear resistance of the filter.  Read the complete study.

Dursan wear resistance 6 12 18


Carbon Coking Fouling Resistance

Coking and fouling studies show SilcoTek® coatings and coatings combined with a surfactant reduce fouling by 50% or more.  Reducing the particulate binding effect and making the filter easier to clean.   

coking heat sink fuels

Corrosion Resistance

ASTM G31 immersion testing compared a Dursan coated surface with silicon and uncoated stainless steel.  The Dursan coated surface improved corrosion resistance by an order of magnitude, improving metal filter durability.  Get our latest on corrosion prevention, get our corrosion presentation.


Surface Energy

A key to particulate binding and fouling is surface energy management.  A low surface energy surface will reduce the particulate bond energy and make filter cleaning easier.  Surfaces like Notak™ (F-Dursan in the graph) offer the lowest surface energy and highest contact angle of any silicon surface tested.  The Notak surface reduces surface energy by 80% compared to stainless steel.  

Surface energy comparison

Read Moisture Resistance And Hydrophobicity Whitepapers


What's it all mean?  How Does a Low Friction Low Surface Energy Surface Prevent Membrane Fouling?

So what will a low surface energy high lubricity filter surface contribute to fouling prevention and improved filter performance?  Let's compare the differential pressure of an uncoated filter (graph below, top 2 lines) with a Dursan coated filter under simulated process conditions.  The coated filter (lower line) had nearly twice the life and half the differential pressure of the uncoated filter.*  That means that Dursan or other SilcoTek coatings can help extend the life of your metal filter while reducing energy loss and system back pressure.

Filter Differential Pressure vs. flow 6 11 18

Interested in fouling resistance?  Read our webinar presentation and learn about how our coatings reduce fouling in many applications.

Learn How To Manage Surface  Energy, Fouling, and Moisture Resistance


Coating Benefits

heat exchanger foulingFouling reduction can benefit many applications including:



*Data courtesy of Porvair Filtration. 

Tags: Oil & Gas Upstream & Downstream

Calculating the Cost of a Corrosion Resistant Coating

Posted by Marty Higgins on Jun 8, 2018 11:43:40 AM


What's the cost of a corrosion resistant coating?  Let's take a look at the real cost of buying and maintaining a corrosion resistant surface.  Hint, buying on the cheap may be the most expensive option. 

Corrosion is not simply a maintenance problem.  Corrosion can have a multitude of adverse effects like poor product yield, product contamination, damage to costly instrumentation, and low productivity.  To the extreme, corrosion can become a real drag on profitability.  According to US Government studies, corrosion costs the US $276+ billion annually, that's why there's a huge market in corrosion control.  But what's the true cost of implementing a corrosion solution?

In this blog you will learn:

  • How Dursan and Silcolloy corrosion resistant coatings perform compared to stainless steel and super alloys
  • Factors to consider when comparing corrosion resistant materials or coatings
  • Get a relative cost of various corrosion resistant materials
  • How life cycle costs can be a major factor in selecting a corrosion resistant material

First Consideration. Is The Corrosion Solution Effective? 

Before we discuss the true cost of a particular corrosion solution it's a good idea to be sure the material or coating in question are chemical resistant and effective in preventing or limiting corrosion.  Let's compare the effectiveness of corrosion resistant materials under various corrosive and temperature conditions. 

Get Our Latest Corrosion Solutions Presentation

The ASTM G31 immersion test (below) compares an uncoated 316L coupon with Silcolloy® and Dursan® coated coupons.  The coupons were immersed in a 20% HCl heated to 50 C.  After 7 hours the coupons were extracted, cleaned and weighed.  Corrosion rates where calculated based on weight loss.  The baseline corrosion solution, stainless steel, had a very high corrosion rate.  Use under similar conditions would require frequent maintenance and could potentially impact production if used in critical performance areas.  The Silcolloy coupon had significantly less corrosion but would likely require regular maintenance.  The Dursan coupon had about 1% of the corrosion rate compared to stainless steel, showing potential benefits to maintenance and operations cost.

HCl corrosion 50c exposure-496019-edited

Comparative ASTM G31 immersion testing in a sulfuric acid solution shows similar performance with the Dursan coated coupon performing exceptionally in the application with orders of magnitude reduction in corrosion rate.

Sulfuric acid G31 corrosion test-168851-edited


Here are images of the sulfuric acid test.  The uncoated 316L coupon (left) is significantly damaged by the sulfuric acid.  Additionally the acid solution is contaminated by the stainless steel, turning the fluid green.  The coated coupons remain undamaged and the sulfuric acid solution is not contaminated.  This could protect process fluids from contamination and improve yields.

Sulfuric acid G31 corrosion picture

Let's throw some superalloys into the mix and see how they perform.  In this comparison, we immersed coupons into 6M HCl for 24 hours and then measured the corrosion rate.  The superalloys, C276 and C22, performed the best, followed by the Dursan and Silcolloy coated coupons.  


We've compared the performance of various surfaces and found superalloys perform the best, followed by Dursan coated stainless steel, and finally stainless steel.  So the most cost effective corrosion solution are superalloys, right?  Well maybe yes and maybe no.  It all depends on the application.  Let's compare the cost of various corrosion resistant products.

How Much Vs. How Effective?  The Cost Benefit of Corrosion Resistant CVD Coatings.

First let's compare the cost of a valve manufactured using a superalloy, Dursan coated, and stainless steel.  The stainless steel valve is the cheapest, a fraction of the cost of Dursan or superalloy valve.  But remember the poor corrosion resistance of the stainless steel?  That poor performance could mean you'll be replacing that cheap valve 10 times during the useful life of the project or system.  That means the stainless steel valve is actually the most expensive at $370.00.  And that doesn't include the labor cost associated with replacing the valve and the lost productivity while the process or product is down.  Depending on application, the Dursan coated stainless steel valve offers a good mix of improved corrosion performance and cost.  For a 4x cost increase you get more than a 10X improvement in corrosion resistance.  The superalloy valve costs about 8x more but does not significantly improve corrosion performance over the Dursan valve (based on ASTM G31 tests).

Corrosion cost analysis Valve

Comparing the life cycle cost of operating a typical stack sampling system shows that after factoring in capital cost and component replacement cost; Silcolloy or Dursan coated stainless steel surfaces are the clear cost leader when compared to high performance alloys and untreated stainless steel.


The Big Concern.  Picking The Best Corrosion Resistant Material For The Application 

Factors to consider when calculating the true cost of a particular corrosion solution include: 

  • The criticality of the application.  If you can't afford downtime or a corrosion failure may cost you a bundle, the superalloy may be good insurance against failure.
  • Length of service.  How long will the part be in service?  If the part is intended to be used for only a few weeks, a stainless steel component may perform just fine.  For intermediate duration or long term use Dursan or a high performance alloy may be a more appropriate and cost effective solution.
  • How sensitive is the process to contamination?  If corrosion particulates or ion contamination endangers product quality or yield, it may be ideal to coat the flow path regardless of duration of use.  For extreme sensitivity to metal ion contamination, coating a high performance alloy with Dursan or Silcolloy may be the most cost effective solution.  Dursan and Silcolloy do not contain metals, making a completely metal free and corrosion resistant surface. 
  • Ease of replacement.  How easy is the part to replace?  Ease of access may factor in selecting a cost effective corrosion solution.
  • Cost of part.  If the part is an expensive instrument probe, it would be highly cost effective to coat the part with Dursan.

It's clear that material cost is not the only factor when selecting a cost effective corrosion solution.  Weigh all factors carefully before committing to a corrosion resistant product.  Want to learn more about improving the corrosion resistance of your product at the fraction of the cost of superalloys?


Get Our Corrosion Webinar


Tags: Oil & Gas Upstream & Downstream

How To Stop Sample Cylinder Corrosion, Make Canister Cleaning Easier

Posted by Marty Higgins on Jun 1, 2018 9:25:00 AM


Did you know that SilcoTek® can coat sample cylinders, small process tanks and canisters with a high purity corrosion resistant coating?  Learn how we do it and how CVD coatings improve the corrosion resistance of tanks, cylinders and canisters. 

Containment vessels can hold a secret.  Because cylinders, tanks and canisters can't be easily examined, they can corrode, hold onto trace contaminants or react with the contents. 

In this blog post you will learn:

  • How corrosion and reactive samples can impact tank or vessel integrity and contamination
  • How Dursan® and Dursox™ coatings can prevent corrosion and contamination
  • How cleaning can be detrimental to contamination, reactivity, inertness, and corrosion
  • How SilcoTek® lines tanks, sample cylinders and canisters with CVD silicon coatings

Be it corrosive or reactive, samples, process fluids, or high purity materials need to be protected from reactive surfaces.  Canisters or other containment vessels are typically constructed of stainless steel, carbon steel, or other metal alloys.  They do a great job of holding materials under pressure but it's difficult to be sure the tank surface is not reacting with process materials.  Problems include:

Inspecting the tank to be sure there's no contamination can be problematic.  Inspection probes give a myopic vision of the tank surface and it's easy to miss critical parts of the tank like threads and shoulder areas.  Regular cleaning of the interior surface is critical to assuring the surface is clean.  But cleaning can have it's own problems including:

  • Aggressive cleaners can themselves corrode the surface
  • Cleaners can leave a residue that can be reactive
  • Cleaners can be inadequate and leave trace process chemical behind to cross contaminate subsequent refills
  • "Sticky" process chemical may be left behind
  • Process or analytical samples can reside in pitted or rough surfaces or in threaded areas
  • Moisture contamination due to aqueous cleaners

 Get Tips on Cleaning Analytical Flowpaths


Make canister cleaning easier & more effective and while improving corrosion resistance

Applying a CVD coating to the interior of tank surfaces can benefit tank performance and cleaning effectiveness several ways:

  • Inert coating eliminates surface reactivity
  • Silicon barrier coatings like Dursan® or Silcolloy® bond to tank surfaces and improve corrosion resistance
  • Dursan, and other SilcoTek coatings offer non stick properties that prevent "sticky" compound from bonding to the surface, reducing carryover contamination and cross contamination.
  • Notak™ coating and Dursan repel moisture, making cleaning more effective and preventing moisture contamination.

Our patented CVD coating process apply non reactive and corrosion resistant silicon to stainless steel (or other metal alloy) canisters to both inside and outside surfaces.  Our micro thin silicon barrier coatings do not change the dimension or tolerance of the canister, allowing the customer to easily improve existing tank performance. 

Get Our Latest Corrosion Solutions Presentation


Improved tank inertness, purity and corrosion resistance

Test data show a silicon surface bonded to stainless steel can prevent interaction of the flow path material with the tank surface, preventing ion contamination, corrosion resistance and leaching of impurities into the process.


Read How To Set Up Your  Own Inertness Test

Inertness and purity

SilcoTek's Dursox coating (a silicon-oxide Dursan coating) protects your product from contamination because Dursox® contains no metals.  X-Ray photoelectron Spectroscopy (XPS) analysis (below) show no metallic contamination up to 10nm into the Dursox surface.  Assuring a contaminant free canister. 

High Purity Coatings presentation thumbnail


Canister Corrosion resistance

72 hour hydrochloric acid immersion testing show Dursox significantly improves corrosion resistance of tanks and containment vessels.  Dursox is a metal free CVD coating that improved corrosion resistance without the use of plastics or metals.  More importantly the process liquid (in this case hydrochloric acid, HCl) remained stable and was not contaminated by iron leaching or exposure to the stainless steel surface.  The beaker on the right shows a clear HCl liquid.  If the stainless steel were attacked by the HCl the liquid would have turned dark green.

Dursox_corrosion_Comparison_2_18_15 Dursox_HCl_imersion_10_08_15_

 Want to see more corrosion data?  Get Our Latest Corrosion Solutions Presentation


How We Apply Our Coatings To Tanks, Canisters or Sample Cylinders

Coated sample cylinders

Our chemical vapor deposition process is not line of sight.  That means we can coat not only exposed surfaces but also internal components and surfaces.  All areas of the tank both internal and external surfaces including threads are coated.  The micro-thin coating does not interfere with threads or other high tolerance surfaces like conflat flanges or compression sealing areas.  The coating gas when exposed to metal surfaces under temperature will bond to the tank surface, making a uniform and highly durable coating.

 Dursan process graphic 2 4 4 18


CVD coating applications

SilcoTek® coatings can be applied to a wide range of canister geometries and surfaces


SilcoTek coated conflat flange
  • Whole air monitoring canisters
  • Sample cylinders for oil and gas applications
  • Storage tanks
  • Calibration gas cylinders
  • Canisters for hydrogen peroxide reactivity in semiconductor ALD 
  • Tanks and vaporizers for HBr in etch applications
  • Tanks for acid cleaners
  • Tubing, fitting and valve flow paths
  • Conflat, compression, VCR, and other sealing surfaces.


Improve Material Performance Watch Our Webinar

Tags: Oil & Gas Upstream & Downstream

New IMO Regulations Will Drive Up Low Sulfur Distillate Demand

Posted by Marty Higgins on May 25, 2018 10:21:18 AM

Container ship

In 2016 the UN International Maritime Organization (IMO) took a stand for cleaner air by setting stricter standards for sulfur content in fuel oil used to power global shipping.  Don't care about shipping?  Don't think this new standard has anything to do with your business?  You're sadly mistaken.

 A May 2018 article in Marine Link Magazine "New Rules on Ship Emissions Herald Sea Change for Oil Market" by Libby George and Ahmad Ghaddar discusses the potential impact of a new sulfur emission regulation promulgated by the UN IMO.  After reading the article, I realized the far reaching impact the regulation will have not only on global shipping but how this regulation could impact everything from the price of an airline ticket to the cost of my Amazon Prime!  

In this blog you will learn:

- How the New IMO rule could cost you more for shipping

- How demand for low sulfur sweet crude could increase

- How refinery capacity for production of marine gas oil will be stretched to the limit

- Opportunities for better sulfur management and detection systems

About the IMO rule and global shipping

About 3 million people world wide die every year from air pollution.  One of the primary killer pollutants is sulfur emissions from buring fossil fuels.  To combat the world air pollution epidemic and to reduce sulfur emissions, the UN International Maritime Organization set stricter standards for sulfur content in fuels in an effort to improve world air quality.  By 2020, the regulation requires the use of 0.5% sulfur fuel oil (down from the current permitted 3.5% sulfur).  Vessels that continue to burn 3.5% sulfur fuel will be required to install exhaust scrubbers.  Violators could find themselves in hot water including:

  • Fines
  • Insurance coverage problems
  • Potential declaration the ship "unseaworthy", preventing it's use on the high seas 

Ship exhaust stack-448052-edited


The shipping carrier has a few options regarding the new IMO regulation.  They can choose to pay the higher fuel costs associated with purchasing low sulfur distillates.  They can install scrubbers on the ship.  Or they can cheat and risk essentially losing the vessel to an unseaworthy declaration if caught. 

None of the options for shipping operators are particularly compelling.  Demand for distillates like marine gasoil will likely spike.  Given the limited supply of distillates, prices for low sulfur distillates could result in a fuel cost increase of $6K to $20K per day.  That could mean billions in increased costs for shipping.  Scrubbers would allow a ship operator to continue to burn the less costly high sulfur fuel but entails an expensive scrubber installation.  Scrubbers can cost millions per ship which can stress the capital budget.  More importantly there are only so many companies with the expertise to build and install a scrubber system on a large vessel.  The overall capacity for scrubber installations is estimated to be about 500 vessels per year.  At that rate it would take about 100 years to convert all 60,000 vessels.  Not a realistic option.  Speaking of not realistic, cheating is not a viable option for most major shipping firms.  The risk to reputation and the bottom line is too great, especially considering new "black box" emissions technology that could provide real time sulfur emissions data. 

Get Our Inert Coatings Presentation

Why is this a big deal?  It all has to do with the fuel source, the refinery. 


Global shipping is the cornerstone of world trade.  Approximately 90% of manufactured products are shipped by bulk carrier including consumer products, equipment, and crude oil.  About 60,000 vessels burn 4 million barrels of fuel oil a day while plying the seas.  That's about the equivalent production of the number 4 oil producer and about 40% of production in the US.  So a change in sulfur requirement is not trivial to world markets and refineries, here's why.

Not all oil is the same and a refinery is not just a refinery.  The sulfur content in crude oil varies generally by region (there's variation in individual wells but in general, regions produce sweet (low sulfur) or sour (high sulfur) crude.  For example Saudi Arabia oil is generally lower in sulfur content while Venezuela crude contains higher levels of sulfur.  Refineries exist to process crude oil into petroleum products like gasoline, jet fuel, or marine fuel oil.  It would be costly and inefficient to build a refinery to be able to process all types of crude or crude products so they specialize in a particular type of crude and petroleum products.  For example, a refinery may be constructed to process a light sweet crude (a higher cost crude but cheaper to process into petroleum products) or the refinery owner will design the refinery to process higher sulfur crude (lower cost crude but higher processing cost).  It all depends on the complex cost calculation of refinery location, their cost structure, the deal they have with the crude producer, proximity/shipping costs, etc.

I'm getting bored, what's all this got to do with my Amazon Prime?

OK, OK I'll get to the point!  There's only so much low sulfur distillation capacity in the world.  Just as there's only so much low sulfur crude.  The expected shift to low sulfur fuel will significantly increase demand which, you guessed it, will increase the price of those fuels.  The price pressure will spread to diesel, jet fuel, and perhaps gasoline (depending on the refiner's crude source).  How will this effect shipping costs?  Let's use Amazon as an example.  Let's say I've just ordered some great man gadget from Amazon, using my Amazon Prime account.  The gadget shipped from China by boat (first potential for added cost due to higher marine fuel prices).  The package  arrived in LA and is flown to the Eastern distribution center (second area for an increase due to higher jet fuel cost), shipped by truck to local distribution center and (more cost due to higher diesel prices) and finally delivered to my door (again higher diesel cost).  All that low sulfur fuel demand will surely increase shipping costs and ultimately will lead to an increase to my Prime account!  Think of something you buy that does not depend on fuel costs.  Not many things, maybe happiness, but you can't buy that...

The Importance of Low Level Sulfur Analysis

All the extra cost and effort will be worth it for one important reason.  Our air quality will improve!  

The importance of low level sulfur analysis has never been more clear.  Testing fuels and monitoring air quality is a vital pillar to enforcing clean air regulations.  Unfortunately stainless steel sampling surfaces will adsorb or retain sulfur.  Sulfur adsorption can cause multiple problems for the refinery including:

  • Regulatory emissions compliance
  • Poor product quality (if the sulfur content of your fuel or refined product is higher than you think it will cost you in the long run and will make an angry customer)
  • Calibration problems.  Sulfur loss due to sulfur adsorption will cause calibration errors.
  • Higher cost.  Sulfur contamination can damage catalysts, causing increased catalyst replacement cost.

Improving sulfur analysis = better products and emissions compliance.

To prevent loss of sulfur during testing, coat the entire sample flow path with SilcoNert® or Dursan® coatings.  SilcoNert and Dursan are barrier coatings that act as an inert non reactive surface.  A non reactive surface ensures that all the sulfur sample makes it to the detector.  When all the sulfur is completely and consistently transported to the detector, calibration is easier and the test is accurate and repeatable.  Even after 14 days, sulfur samples remain unchanged as seen in the 14 day stability test (below left).  The uncoated sample flow path (below right) completely adsorbed the sulfur sample within hours of exposure, resulting in test failure or poor product quality.

14 day sulfur stability 3 copy-732537-edited-251656-edited Sulfur_loss_in_stainless_steel_cylinder_2

Why is sulfur hard to sample and detect?

Because sulfur and sulfur compounds tend to stick to materials commonly used in sample flow paths.  If the sulfur gets trapped in the flow path, the instrument can't accurately record the data, making control of scrubbers and processes difficult at best.  Here's an example of how sulfur can get lost in a tube.  Shell and O'Brien conducted a study where a sulfur compound was injected into a tube.  Then they waited for the detector at the other end to "see" the sulfur.  They waited... and waited... and finally after 90 minutes some sulfur hit the detector!  Here's a graph of the test results.


The first red line is a graph of the sulfur response when that tube is coated with SilcoNert®.  Under the same test conditions the response is almost immediate!  Virtually no sulfur was lost in the tube.  When all the sulfur makes it to the detector, the plant, ship or refinery can accurately monitor and control emissions and process; making for a better product while minimizing sulfur related air pollution.

Read The Entire Sulfur Detection Study By Shell and O'Brien Analytical

How big a problem is sulfur adsorption?  Well if we look at the US EPA Tier 3 standard, a 10ppm sample will be completely lost in a relatively short length of sample tubing.  If the sample were exposed to a high surface area metal (for example if a sample were filtered through a sintered metal frit), most if not all of the sample would be adsorbed onto the surface.  

SiltekLiners_ph_so_lnr_copyHere's an example of how dramatic sulfur loss can be.  A sample of hydrogen sulfide, carbonyl sulfide, and methylmercaptan were injected onto a GC column through a 3 inch long stainless steel liner.  During the brief exposure to the stainless steel liner, the sulfurs adsorbed onto the stainless steel surface.  The adsorption was so complete that the detector was not able to see any hydrogen sulfide (H2S) or mercaptan (image below).  If we rerun the test using a SilcoNert 2000 coated liner, the H2S and mercaptan are clearly picked up by the detector. (second graph).

Sulfur loss on stainless steel liner    

How do SilcoTek® inert silicon CVD coatings improve sulfur sampling and air quality?

Our inert CVD coating, SilcoNert®, provides a barrier between the sample and the reactive stainless steel surface.  That allows the sulfur or NOx sample to pass right through the flow path without interacting with the surface, delivering the entire sample to the detector.  Our inert coating benefits include:

Want to lean more about analytical sampling and how surface science can improve results?

Ultimate Guide to Reliable Analytical Sampling


Tags: Oil & Gas Upstream & Downstream

Coking and Fouling Prevention in Refinery Applications (CVD Coatings)

Posted by Dr. David Smith on May 18, 2018 9:22:33 AM


Can SilcoTek coatings prevent fouling and coking in refinery applications?  Read on and get some pretty impressive results!

In this blog you will learn:

  • How fouling impacts refineries
  • Problems with current fouling solutions
  • How inert anti fouling coatings can prevent coking or reduce fouling
  • Learn about CVD anti fouling coating solutions and fouling prevention


Fouling can severely impact the performance of processes and instrumentation in just about every industry.  The effects of the accumulation of substances, be it carbon fouling in a distillation process or the build up of carbon particulates in fuel systems, can have a range of impacts: 

Impact of fouling on refinery and fuel systems.
  • Causes contamination
  • Reduces flow
  • Increases drag/pressure
  • Encourages corrosion
  • Increases emissions
  • Increases maintenance requirements
  • Slows production
  • Costs money!
heat exchanger fouling.png

Dealing with the impacts of deposits and build-up of unwanted materials depend on the application and importance of the process.  Regardless, the cost can be high.  Here are some examples of the impact of material build-up on critical surfaces:

  • Refining
    • -$0.5 billion spent to overcome coking issues (2002)
  • Heat exchangers
    • -50% of maintenance costs are caused by deposits, causing billions of dollars to industry.
  • Automotive
    • -10%+ increase in fuel consumption due to fouling


Read our presentation on preventing coking and fouling


Fouling Prevention in Refinery Applications

There are many possible solutions to the problem.  Some expensive, some not realistic, most are costly and can result in redesign or added maintenance.  Here are a few examples:

Solution Issue
Additives Costly, difficult to manage. May not be realistic for some processes
Steam cleaning Not entirely effective.  Impacts productivity.  Not realistic for some processes.
Increase energy / power / fuel consumption (basically brute force idea) Expensive and does not solve the problem
Control the incoming media that’s causing deposit build-up Rarely an option in industrial applications
Material selection Several options, difficult to optimize performance & cost
“Surface engineering” through advanced anti-fouling coatings 

Flexible and cost effective

Modify the existing part’s surface to make it behave how you need it to


The Benefits of Coatings to Prevent surface interaction

emissions-smoke_stack_EPA_SilcoNert Flowpath 

Inert CVD Coatings can be an effective solution for multiple applications and industries because they enhance the performance of the surface while preventing interaction of the base material with the interacting substance.  The result?  A better surface without changing the part design or physical property of the base material.  There are, however, several factors to consider when selecting the right coating for the application.  Such as:

-Do I have to re-engineer to account for tolerance changes?  In most cases no change in tolerance needed.  But consider for super high tolerance applications.

-Is there an environmental impact?  The amorphous silicon surface has very little environmental impact both during processing and as a product.

-Can the anti-coking coating withstand temperature, abrasion, corrosion, etc. in the application?  In many cases, yes but consult with a SilcoTek representative to be sure.

-How long will it last?  Depends on the application, but the coating should provide superior performance for years.  Contact a SilcoTek representative to discuss your application.

Want to learn more about our coatings and how they improve the performance of your product?  Get our webinar on demand.

Solving coking and fouling problems

How SilcoTek Coatings Prevent carbon build-up and fouling


SilcoTek coatings are an inert high temperature barrier coating, preventing catalytic or chemical interaction with the underlying surface.  For example nickel containing substrates catalytically form carbon deposits (coke) from petrochemical media. Causing build-up on the surface.  Coatings like SilcoKlean® or Dursan® bond to the surface and change the surface energy and inertness, preventing chemical adhesion and adsorption of the substrate.  The coating's low energy surface prevents the attachment of flow path chemicals to the surface.  Applications include:

SilcoTek® Solutions & Applications    
Problem SilcoTek Coating Solution  
Carbon deposit, coke, formation from incomplete burning of fuel SilcoKlean barrier coating reduces catalytic coking and carbon deposit formation coking heat sink fuels.jpg
Bio-fouling in food applications.  Spores from sour milk suspensions stick to testing equipment Dursan prevents sticking by up to 76% Residue from sticking.png
Protein binding in medical diagnostics Dursan prevents surface interaction and sticking Protein_adsorption_graph-666998-edited.jpg
Carryover in GC & HPLC chromatography Dursan corrosion resistance prevents pitting & sticking to flow path surfaces Corrosion_Solutions_Dursan_Graph_10_16_13-118258-edited.jpg

SilcoTek offers many solutions to the problem of sticking, corrosion, deposits and carryover.  Go to our solutions page to learn more about our coatings.

 See How We Perform  In Your Application


Tags: Oil & Gas Upstream & Downstream

How To Remove Rust From Sample Probes & Prevent CEMS Corrosion

Posted by Marty Higgins on May 11, 2018 9:44:00 AM

power station 

Stainless steel is typically specified because of its ability to resist corrosion in a variety of environments. Unfortunately, stainless steel is not completely corrosion resistant.  That's particularly evident in stack probe, sample probe and CEMS applications where corrosion can quickly damage probes and result in system shutdowns or regulatory compliance problems.  Here are some tips on how to remove rust from sample probes and prevent CEMS corrosion.

Exposure to corrosive process fluids and cleaners, high humidity or high salinity environments such as sea water can remove the native protective layer (chromium oxide) and can cause stainless steel corrosion.  Removing surface rust from surfaces improves the appearance, but it's importance goes beyond the decorative.  Rust, left unchecked, can lead to pitting and structural damage to products and components and can impact the performance of instrumentation, contaminate flow paths, and impact reliability. 

So what is the most effective way to remove rust from stainless steel?  

Before Rust Removal

Corrosion photo

After Rust Removal

Corrosion photo 2

The best method will effectively remove surface rust, but minimize impact to the bulk stainless steel substrate.  Abrasive techniques like sandblasting, abrasive pads, or abrasive rubbing compounds can damage the surface finish and embed particulates into the surface.  Two methods used by SilcoTek® to remove surface rust employ weak acids.

Read Rust Removal Whitepaper

 Phosphoric Acid

Phosphoric acid will dissolve iron oxide without attacking the other components of the steel (chromium and chromium oxide, nickel, and iron).  The rust is dissolved by the following reaction: 2 𝐻3𝑃𝑂4 + 𝐹𝑒2𝑂3 → 2 𝐹𝑒𝑃𝑂4 + 3𝐻2𝑂

Phosphoric acid is readily available from a number of commercial suppliers (SilcoTek uses 85% ‘food grade’) and it can be used with no dilution because of its non-aggressive nature. Clean up after acid treatment is done by thoroughly rinsing parts in deionized water to remove any remaining acid on the surface.  If deionized water is not available, rinse with distilled water.

Unfortunately, this technique is not 100% effective on all the forms of iron oxide and other surface preparation treatments could be necessary.

Acetic Acid

The reaction with acetic acid is often slower than phosphoric acid and can be a better choice when the underlying corrosion/staining affects a larger percentage of the substrate.  Read the entire report.  Following the acid exposure, parts must be rinsed thoroughly with deionized water to assure complete removal of trace acid.  

Watch our sonication video to see how to sonication removes particulates.

Once the rust is gone, keep it off.  Ways to prevent stainless steel rust.

Once the rust is gone, use high durability silicon coatings, like Silcolloy® and Dursan® , to improve the corrosion resistance of stainless steel and other alloys.  Read more about corrosion solutions.  

Process analyzers and process sampling systems can be exposed to challenging corrosive environments both internally and externally.  Many sample streams contain reactive compounds that reduce equipment lifetime or require extended preventative maintenance. Some systems are exposed to environments such as sea water and salt spray, which cause rapid deterioration of equipment, requiring extra cost to keep them operating.  Or the sample stream itself can be highly corrosive like streams found in stack or flare systems.  For systems that are required to give accurate, reliable and repeatable data in such conditions, the cost of upkeep and maintenance can be excessive in both dollars and lost yield or productivity due to plant or system outages.  That's why it's important to find ways to improve the corrosion resistance of components rather than just constantly removing rust from surfaces.

Get Our Latest Corrosion Solutions Presentation

Salt Spray Exposure Testing

Salt spray immersion tests show Dursan significantly improves salt corrosion resistance, extending the useful life of 300 series stainless steel from days or weeks to years.  After 250 days of salt spray exposure the Dursan coated coupon looks like new while the uncoated stainless steel coupon is rusted.


EIS data ( Electrochemical Impedance Spectroscopy)  show Dursan remains pinhole free after over 250 days of salt spray exposure.  Stainless steel exhibits significant pin holing after a few days as seen by the divergent impedance plot on the left.  The Dursan graph (right) does not change, indicating no change in pinholes.


Stainless Steel: Significant Pinholes


Dursan: No Pinholes


 After 247 days, Dursan continues to be pinhole free.

Salt spray EIS Data.jpg 

Acid Exposure

Depending on the specific alloy, 300 series exposure to aggressive acids can range in durability from a few hours or days to a year or so before failure; not a great model for reliability.  Generally, high levels of acid will spell trouble for 300, 304, or 316 stainless steel. 

Table I provides the results obtained from ASTM G31 testing.  This method is an immersion test for 24 hours in a 6M hydrochloric acid (HCl) (18%) solution at room temperature and pressure.  After immersion, differential weighing allows the amount of material loss to be determined.   The Dursan coated surface significantly improves chloride corrosion resistance. 

Table I:  Weight loss after 24 hour exposure to 6M (18%) HCl

24hr; 6M HCl; 22ºC

304 SS

Silicon coated

Dursan coated

MPY (mils-per-year)




Improvement Factor




Comparing multiple coupon materials, Dursan® demonstrates similar performance to costly super alloys.  After 24 hours of exposure to concentrated hydrochloric acid, the Dursan coupon compares favorably to alloys.  The best part?  Dursan can be applied to stainless steel without significantly impacting durability or tolerances.  So you can use existing parts or designs and enhance the corrosion performance without redesign or re engineering.



In some ways the easy part of corrosion prevention on stainless steel is removing the rust.  The hard part is keeping the rust off without costly component redesign or re manufacture.  You can keep your components and improve corrosion resistance by bonding a high tolerance, high durability, corrosion resistant coating to the surface after rust removal.  

Remember to use the least damaging but still effective rust removal and cleaning method on parts.  Highly aggressive rust removal agents and cleaners can etch part surfaces, creating sites for renewed corrosion or damaging surface finish, seal areas or flow paths.  If it is not possible to apply the removal techniques at your facility, SilcoTek’s sales group can provide a quote for the acid cleaning process upon request.  Click here to get a coating or cleaning quote.

Want to see our coating fight corrosion?  Watch our corrosion video!






Tags: Oil & Gas Upstream & Downstream

How Notak Coating Prevents Fouling and Improves Hydrophobicity

Posted by Marty Higgins on May 4, 2018 9:05:17 AM

Hydrophobic surface drops

We developed a moisture repelling super hydrophobic coating that's also an excellent non stick coating for mold release and fouling prevention.  Read on to learn more.

Notak™, a super water repelling surface with benefits.

We're looking forward to a new coating our R&D team has been developing.   Full disclosure, we're still working on the final coating product and process details, but we can offer limited evaluation/beta test samples.  If you're interested in learning more about our new Notak  fluoro based coating, contact us and we can discuss your application.


About Notak™ Coating

We recently developed a new fluoro chemistry based coating that proved to be super hydrophobic and have interesting surface properties that have anti fouling or non stick properties that improve mold release. 

Learn How to Improve  Injection Mold Performance

Moisture resistance


Hydrophobic coating demo 7 17 17-1-968266-edited.jpg

To demonstrate the super hydrophobic nature of the new fluoro coating Dr. Smith (our R&D director) sprayed water on the coating to see if the water wetted the surface.  The water stream bounced off the coated part without getting the surface wet, showing excellent moisture resistance.  Watch our video to see how the new fluoro coating resists moisture.



Get more information about

hydrophobic and corrosion resistant coatings.


About Hydrohobicity and Oleophobicity: a Comparison

A hydrophobic surface is a water repelling, low surface energy surface that resists wetting.  Moisture contact angle measurements will classify a surface as hydrophobic when the contact angle of the water droplet exceeds 90 degrees.  Exceed the 150 degree contact angle mark and the surface will be classified as superhydrophobic.  Water will jump right off the surface as seen in this video.

There are many benefits of a moisture repelling surface.  They include:

- Surface icing prevention - Condenser & evaporator fouling prevention
- Improved corrosion resistance - Prevent moisture contamination in heat trace tubing 
- Produced water filtration & management - Improved reliability in continuous emissions monitors (CEMS)
- Improved moisture detection instrumentation - HPLC medical diagnostics improved separation & corrosion resistance
- Manage moisture contamination in liquid natural gas systems - Prevent contamination in analytical sample transfer systems


High Temperature Hydrophobicity 

SilcoTek's new coating, Notak, achieved significant improvement in hydrophobicity and oleophobicity compared to the uncoated DLC surface.  More impressively, the new coating remained stable when exposed to high temperatures for over 24 hours.  Both hydrophobicity and oleophobicity contact angle were unchanged over the test period, indicating stable surface energy.  

New Coating Hydrophobic and Oleophobic


How do I get a surface to match my desired moisture level of moisture resistance?

You don't have to make a super radical change to material or product construction in order to change the moisture performance.  Fortunately we offer silicon barrier coatings with a wide range of water management capabilities.  Want a more corrosion resistant or inert coating with a low surface contact angle?  Try SilcoNert® 1000 or Silcolloy®.  If you're looking for an inert coating that's not too moisture repelling, go with SilcoNert® 2000.  Need maximum water repelling coating properties?  Dursan® or our new Notak coating may do the trick.  Note, our Notak coating is in pre-production Beta testing so we have limited capacity for that coating.  Contact our Technical Service Team to discuss your application and we'll be happy to make a coating recommendation.

Notak hydrophobicity static CA


The comparative graph above highlights the water repelling properties of each of our coatings compared to stainless steel; each coating has specific applications and benefits.  Go to our applications guide to get the lowdown on each of our coatings.  Or watch our webinar.

Solving coking and fouling problems


Hydrophilic Surfaces

Not to be outdone, hydrophilic surfaces have benefits as well.  What are hydrophilic surfaces?  They are high surface energy substrates that attract water and allow wetting of the surface.  They typically have a droplet contact angle measurement of less than 90 degrees.  Lots of surfaces tend to be more water friendly including, glass, steel, or stainless steel and many coatings and paints.  Of course test results can depend on the surface roughness and surface energy of the material you're testing.

Learn How To Improve Moisture Resistance, Fouling Resistance, and Corrosion Resistance.   Get Our Presentation.


Benefits of a moisture friendly surface include.

- Improved separation in medical diagnostics (application dependent) - Improved efficiency in heat transfer devices & heat exchangers
- Improve acceptance of In-body devices - Improve surface interaction in filtration devices (application dependent)



High Temperature Oleophobicity

Low surface tension liquids like oil or organic solvents are designed to wet the surface for maximum lubrication or solvation.  But what if you're separating organics or don't want the surface to wet?  Water repelling materials like PTFE aren't effective in repelling oil.  Here's what oil and hexadecane look like when placed on a PTFE surface.

Hexadecane on teflon 29.7 degree contact angle-401247-edited.png oil on teflon 48.5 degree contact angle-515333-edited.png

We bonded our new Notak oleophobic coating on a rough stainless steel surface to see if the contact angle would increase.  Notak made a big difference in contact angle, making the stainless steel an oleophobic surface.

hexadecane on rough fluoro 92.6 degree-142340-edited-531970-edited oil on rough fluoro 95.5 degree-075556-edited-682056-edited

Given the nature of refining or cleaning processes for that matter, we can expect the surface to be exposed to elevated temperatures.  PTFE is high temperature limited and can fail in many high temperature applications.  We exposed the Notak surface to elevated temperature (300°C) for several hours to gauge the impact to wettability, high temperature oleophobicity, and contact angle on various surfaces.  The graph below shows consistent contact angle readings over the 90+ hour test.  PTFE would have failed at 250°C. 

Oxidative stability, oleophobicity fluoro surface.pngThe contribution of surface energy and it's relationship to process fluids can have far ranging impacts.  Surface interaction can impact corrosion, fouling, analytical sampling results, filtration and medical device performance.  So it's important to understand how to manage the energy of critical flow path surfaces.

Get some informative and helpful tips on ways to prevent fouling, change surface energy, & improve surface performance.

Learn How To Manage Surface  Energy, Fouling, and Moisture Resistance


What else can the coating do?  How about a non stick coating that offers better mold release. 

Well we're not sure about all the potential uses, but we're finding great success in plastic mold release applications.  It turns out the coating promotes better release of product from plastic molds and can prevent fouling in some applications. 

Learn How to Improve  Injection Mold Performance

Here are some mold release benefits of Dursan and our new fluoro surface:

  • Better wear resistance for higher durability, and erosion prevention.
  • Higher lubricity to improve operation of moving cores and slides and improved resin flow for reduced energy cost and wear.
  • Prevents contamination by oxidation by products in medical and electronic applications.
  • A change in our luminescent release agent rainbow finish signals a loss of coating.  Visual inspection of the surface signals coating loss without precision measurement. 
  • Mold complexity does not significantly impact coating price. 
  • Eliminate Diamond finish release problems by improving surface lubricity.  


If you want to learn more about fouling prevention and mold release read the latest article in AZOM: 

Improving and Protecting Industrial Applications With Anti-Fouling CVD Coatings

Contact our Technical Service Team and we'll be happy to discuss details about the coating. 

Have another material problem?  Get our applications guide to learn how SilcoTek can improve the performance of your products.

 Get our coating application and properties guide.


Tags: Oil & Gas Upstream & Downstream

How To Test a Coating for H2S Resistance and Sulfur Inertness

Posted by Marty Higgins on Apr 27, 2018 11:16:05 AM


Customers interested in improving instrument sensitivity and precision often evaluate the coating surface for reactivity to confirm the coating meets performance parameters.  But what's the most effective way to test a coating for inertness and purity?  Let's find out.

Testing and evaluating a coating or surface for adsorption, non reactivity, inertness and purity can be a challenging undertaking, especially when testing reactive compounds at trace levels.  If you're having trouble figuring out how to evaluate a coating, you're in luck!  We've got 30 years of experience recommending processes or methods to use when evaluating an inert coating or surface.  Here are a few tips we've learned over the years.

In this blog you will learn:

- Tips on how to evaluate a surface for chemical inertness and reactivity

- How selection of test compounds and concentration affect results

- Get sources for inertness test design standards and specifications

- Get ideas on test system design

Selecting The Compound & Concentration for Sulfur Inertness Testing

How do I know a surface is inert for my test?  That's a tough question to answer.  A surface may perform very well for one compound but not for others.  Additionally, a surface may be adequate for higher levels of concentration but not for trace analysis or speciation.  Let's first discuss compound selection, then we'll expand the discussion to concentration.

Selecting the compound for sulfur testing & surface evaluation

If you have one compound and don't expect to test other reactive chemicals then picking a compound to test is pretty straight forward; just pick that chemical at the expected concentration and run the test.  Of course you'll need to run a statistically significant number of runs (say n=5) and test a few coated flow path component samples to assure repeatability, but overall a pretty easy method to evaluate inert surfaces.  Before testing it's always a good idea to understand the capabilities of the coating or surface.  Here's information on our coatings:

Go To Our Coating Material Property & Specifications Page

Unfortunately most analytical systems will be exposed to several active compounds over the life of the flow path.  In this case things can get complex quickly.  Unfortunately you can't test all reactive compounds, there are millions of chemicals out there so testing them all would take just a few minutes short of forever.  Rather than spending the rest of your life evaluating various flow path surfaces, consider testing a class of reactive compounds rather than all potential analytes.  For example, endrin and DDT are excellent environmental test compounds because they rapidly degrade when in contact with a reactive surface, especially if it's a hot surface. 

Chromatography companies offer good reference source material for selecting chemical standards containing target compounds for your analysis and surface needs, be it environmental testing, clean air standards, whole air monitoring standards or oil and gas sampling.  The standard can be sourced from several companies that offer calibration samples.  If you're testing lots of compounds the standard can get expensive pretty quickly so be judicious in your selection. 

Here are a few links to relevant company information on sourcing chemical standards.



Concentration matters

OK I've selected my test compounds, is that it?  Sorry no.  You'll need to select the compound concentration.  In many ways concentration is as important as the test compound.  Take sulfur analysis for example.  A stainless steel surface may yield perfectly fine results at percent level analysis but sample at part per million levels and it's a completely different story. 

Sulfur is known to adsorb or "stick" to stainless, glass or ceramic flow paths.  But flow enough high concentration sulfur through the flow path and the active surface will be seasoned or primed to the extent that tests will yield reasonably good results.  However at ppm or lower levels, sulfur will be adsorbed onto the surface because there's not enough of the analyte to adequately "prime" all the active sites.  So virtually all the sample is lost.  Here's a chart comparing the loss rate of trace H2S.  You can see that virtually all H2S is lost within an hour of exposure.  The SilcoNert® coated surface adsorbs virtually no sulfur compound.


Factors to consider when selecting concentration include:

  • Regulatory requirements
  • Industry or customer standards
  • ASTM recommended methods
  • Internal specifications

Setting a lower concentration limit to use for a coating evaluation may depend on the lower calibration point for the instrument or system.  To establish that baseline, find any relevant regulatory or industry standards that dictate a calibration sample range.  Often you'll need to test a system for levels lower and higher than the established range of operation.  So for example a calibration run for a flare CEMS may require a total sulfur sample be run at a low side of 5ppm and a high range of 200 ppm for an operation range of 10 to 150ppm.  The high range sample may be relatively easy to achieve but all sorts of gremlins can pop up when dealing with a 5ppm sample.  Some factors to consider when testing at low levels include:

  • Faster expiration of the standard or stability of the chemical standard
  • Contamination and cross contamination
  • Adsorption by an uncoated reactive fitting or fritted filter
  • Seal material like o-rings that may be reactive
  • Moisture contamination may cause adsorption
  • Corrosion related particulate adsorption
  • Seams or pinholes that promote cross contamination or trace sample loss
  • Cleanliness of the system
  • System surface temperature, phase change
  • Detector or instrument sensitivity to the target compound

The details make a big difference when testing reactive samples at low levels.  Take note system parameters and any changes made during the test to assure an apples to apples comparison and to avoid "getting lost in changes" while troubleshooting a system.   

Get 7 Tips For Improved   Analytical Sampling

System Design, Testing an Inert Coating for H2S Resistance

Test system example 4 25 18

 So you're all ready to go!  You've got the samples at the right concentration, you've got the test method (or ideas of a method) based on industry, regulatory or company procedures.  But what about the test system itself?  Here are a few ideas to be sure you get reliable, accurate test results.*

The test system may be set up in accordance with regulatory or industry practices; when evaluating a surface always take into consideration the following: 

  • Apples to apples.  Don't change the test conditions during the evaluation
  • Nooks and crannies.  Minimize surface pin holes, threads grooves or other areas where a sample can get trapped and cross contaminate a test. 
  • Combining reactive surfaces with inert surfaces.  You can't test an inert surface by placing it in line with a reactive surface.  For trace analysis the sample will be adsorbed by the reactive areas so a comparison of surfaces would yield the same results.  You'll need to either coat the entire test flow path and compare 2 competing flow paths or select a known inert surface and change only a portion of the flow path for comparison.
  • Minimize flow path complexity.  Keep the test flow path as simple as possible to minimize test variables.
  • Make the exposure time adequate to determine effectiveness.  Either flow through a long tube at low flow or through a high surface area component like a sintered metal frit to be sure there's adequate surface exposure.  Another option would be to test by residence time in a sample cylinder.  This method can take a while (days or weeks) but will allow you to establish the degradation rate of the sample.  To accelerate the test, consider heating the sample cylinder to accelerate the reaction rate.  Here's an example of 15 day comparative testing for sulfur adsorption.  The top chromatographs continue to show sulfur peaks after 15 days for SilcoNert® (Sulfinert®) coated sample cylinders.   Uncoated stainless steel sample cylinders adsorb the sulfur (lower graphs).**
15 day sulfur adsorption test  
  • Seals.  Viton, septa or other seal surfaces can be active.  Minimize the use of polymeric seals to limit adsorption.
  • Instrument capability.  If your instrument is not capable of testing to the desired concentration or is not set up to yield reliable results for a target compound then don't bother evaluating the surface.  Instrument factors to consider are:
    • Detector (designed for the target compound)
    • Appropriate instrument (LC or GC?)  Should be capable of testing in the target sensitivity range for those compounds.
    • Calibration.  Instrument should be calibrated and maintained 
    • Training.  The analyst should be familiar with the instrument and detector.

Take a short cut

Are there papers available comparing surfaces for inertness for your sample?  You bet!  SilcoTek has a considerable library of comparative whitepapers demonstrating the effectiveness of our coatings in inertness applications.  We don't want you to take our word for it, or rely on someone else's test for your application, but reading papers that discuss testing a coating in a particular application can be helpful in getting evaluation ideas or understanding the limitations of a surface.

Want more information? Read industry whitepapers

 *Image courtesy of Restek® Corp.

* *Data courtesy of Restek® Corp.

Tags: Oil & Gas Upstream & Downstream

Silicon CVD Coatings Improve Sulfur Detection & Regulatory Compliance

Posted by Marty Higgins on Apr 20, 2018 12:24:37 PM

power station  

The US is not the only country enacting improved clean air standards.  What's the key to meeting of all the standards?  Reliable sulfur detection and sampling.  Here's how SilcoTek® is improving sulfur detection and helping industry meet clean air standards worldwide.

In this blog post you will learn:

  • The impact of air pollution on the environment and health
  • How sulfur compounds and NOx contribute to air pollution
  • Why sulfur is so hard to sample
  • How to prevent sulfur adsorption in sampling and instrumentation flow paths.


pittsburgh during the day 1I visited friends in Pittsburgh a few years back.  We toured lots of great places around the city but what struck me the most was a single black and white photo at the inclined plane on Mount Washington.  The photo (taken circa 1940 judging by the cars) was of a vibrant downtown Pittsburgh at what appeared to be early evening.  The cars had their headlights on and the scene was gray, dark and gloomy.  What shocked me was the caption:  Downtown Pittsburgh at 12 Noon!  In those days the air quality was so bad that cars needed to turn on their headlights to avoid collisions.  Forget about blue sky, you were lucky to see where you were going! 

That made me think back to a story my mother told me about growing up in the Pittsburgh area.  If she slept with the window open by morning the window sill would be black with dirt and there'd be black under her nose.  She said my Grandmother had to have the wallpaper cleaned yearly just to keep up with all the black particulates from the near by mills.  I can't imagine growing up in that kind of air pollution.  Unfortunately a good portion of the world's population is all too familiar with this scene.  But things are changing.   

Get 7 Tips For Improved   Analytical Sampling

The world is catching on to the benefits of clean air.  China for example has enacted aggressive new standards to improve air quality.  They recognize the benefits of improved health, a stronger economy and a better functioning society.  They realize that fewer air quality related fatalities, less flight cancellations, and fewer pollution related plant shut downs benefit quality of life and the quality of China's economy.  In fact, the world seems to be getting the idea that clean air is important.  Just look at the number of new tighter air standards being enacted throughout the world:

What's the primary objective of all these new air quality standards? Reduction of pollution effects through the detection and control of particulates, low level sulfur (SOx), and NOX emissions

Why control sulfur and nitrogen oxide emissions matters.

Remember that image of Pittsburgh at noon?  Well all that darkness was caused by smog.  The grey haze was formed by sulfur dioxide (SO2) and to a lesser extent SO3 as well as oxides of nitrogen (NOx).  But it's not just the dark cloudy appearance that's a concern, SOx and NOx exposure have a real and lasting effect on the environment and humans including:

  • Breathing problems and lung disease
  • Immune system depression
  • Defoliation due to acid rain
  • Damage to structures due to acid exposure

Sound bad?  How about this statistic.  In 2015, 9 million deaths world wide were attributable to pollution, mostly due to smog.  In China nearly a third of deaths are caused by poor air quality.  Given the facts, it's not surprising that air pollution control has become a major initiative throughout the developed world. 

What's the key to control of SOx and NOx?  Reliable detection.  Without a way to sample and compare pollution levels, measuring the effectiveness of air pollution controls like scrubbers and clean fuels would be impossible.  Unfortunately sulfur is a tricky element to detect. because it tends to stick to all sorts of metals, glass, and ceramics; which are common materials used in sample flow paths. 

Read Inert Sampling  Presentation   

Why is sulfur hard to sample and detect?

Because sulfur and sulfur compounds tend to stick to materials commonly used in sample flow paths.  If the sulfur gets trapped in the flow path, the instrument can't accurately record the data, making control of scrubbers and processes difficult at best.  Here's an example of how sulfur can get lost in a tube.  Shell and O'Brien conducted a study where a sulfur compound was injected into a tube.  Then they waited for the detector at the other end to "see" the sulfur.  They waited... and waited... and finally after 90 minutes some sulfur hit the detector!  Here's a graph of the test results.


The first red line is a graph of the sulfur response when that tube is coated with SilcoNert®.  Under the same test conditions the response is almost immediate!  Virtually no sulfur was lost in the tube.  When all the sulfur makes it to the detector, the plant or refinery can accurately control emissions or their process; making for a better product while minimizing sulfur related air pollution.

Read The Entire Sulfur Detection Study By Shell and O'Brien Analytical

How big a problem is sulfur adsorption?  Well if we look at the US EPA Tier 3 standard, a 10ppm sample will be completely lost in a relatively short length of sample tubing.  If the sample were exposed to a high surface area metal (for example if a sample were filtered through a sintered metal frit), most if not all of the sample would be adsorbed onto the surface.  

SiltekLiners_ph_so_lnr_copyHere's an example of how dramatic sulfur loss can be.  A sample of hydrogen sulfide, carbonyl sulfide, and methylmercaptan were injected onto a GC column through a 3 inch long stainless steel liner.  During the brief exposure to the stainless steel liner, the sulfurs adsorbed onto the stainless steel surface.  The adsorption was so complete that the detector was not able to see any hydrogen sulfide (H2S) or mercaptan (image below).  If we rerun the test using a SilcoNert 2000 coated liner, the H2S and mercaptan are clearly picked up by the detector. (second graph).

Sulfur loss on stainless steel liner    

How do SilcoTek® inert silicon CVD coatings improve sulfur sampling and air quality?

Our inert CVD coating, SilcoNert®, provides a barrier between the sample and the reactive stainless steel surface.  That allows the sulfur or NOx sample to pass right through the flow path without interacting with the surface, delivering the entire sample to the detector.  Our inert coating benefits include:

Sometimes it's not about how fast you can deliver the sample but how long you can hold the sample.  When field operations staff take a grab sulfur sample (be it from the well or from the refinery hydrotreater) they can run into sulfur adsorption problems.  The stainless steel sample cylinder surface will adsorb sulfur starting the second the sample enters the cylinder.  That means time is of the essence when trying to accurately assess if the well is sweet or sour or if the hydrotreater is running to spec.  Sulfur stability in a stainless steel cylinder can be measured in minutes or hours.  After that, it's likely the sample is not indicative of field conditions.  Conversely; SilcoNert® coated stainless steel sample cylinder stability is measured in days or weeks.  That means rather than rushing a sample back to the lab, field technicians can grab and hold a sample for 30 days or more with confidence that the sample is the same as when it was pulled from the field. 


Precise and fast sulfur response allows the plant to better control pollution emissions and avoid plant upsets or regulatory compliance issues.  Improved sulfur, and NOx sampling flow paths give the plant operator the tools to achieve those tighter clean air standards worldwide.  Want to lean more about analytical sampling and how surface science can improve results?

Ultimate Guide to Reliable Analytical Sampling


Tags: Oil & Gas Upstream & Downstream

Where to Buy CVD Coated Parts For Sulfur and H2S Testing?

Posted by Marty Higgins on Apr 13, 2018 9:50:00 AM

Silicon coated sample cylinders  

Did you know that you can buy SilcoTek CVD coated products directly from the manufacturer?  Do you care?  Well you should because it could save you time and money in the long run.

Our network of Approved Partners offer SilcoTek® coated products directly off the shelf to help simplify your supply chain.  We don't sell finished products (only coating services), so we work with leading OEMs and re-sellers to make the purchasing process easier for you.  Now you can buy CVD coated parts for sulfur, ammonia, mercury, or H2S testing directly from the manufacturer.

In this blog post you will learn how buying SilcoTek CVD coatings through OEM manufacturers can benefit your supply chain:

  • Save time - place one order with your supplier and let us handle the rest
  • Lower costs - save on shipping and product disassembly/assembly
  • Simplify logistics - eliminate the need to manage multiple POs and vendors

View OEM Partner Directory

Lots of customers send in parts for CVD coating application.  Our manufacturing lead time averages about 5 business days for most coatings.  We're fast and offer a great product but there is one drawback.  Parts need to be disassembled before sending them to SilcoTek for coating service. 

single-stage_regulator_cross_sectionWhy do I have to disassemble parts? 

In order to coat a part, the surface must be exposed to our coating gases.  We don't need much space (we can penetrate and coat a sintered metal frit for example) but we do need some space.  Areas that are not exposed, like seals or internals of assembled parts may not get a consistent exposure to our process gases.  Surfaces also can't be inspected or adequately prepared for coating so there's a risk of inadequate coating.  As we noted before lots of customers send in their disassembled parts but others really don't want the headache.  It's one thing to take a fitting apart but it's can get sketchy for a novice to take apart a valve or a regulator.  Then there's the time factor.  Some companies or individuals have the resources and knowledge to assemble and disassemble parts but others have to either become fast learners or must pay to have someone properly assemble the part.  That's where our OEM Partner program comes in handy.


No more assembly, Buy CVD Coated Products Directly From The Manufacturer.

Scott_regulatorWe've partnered with some of the best manufacturers in the industry to offer SilcoTek® coated products.  They recognize our coatings are the best in the industry and want to improve the performance of their products (here are just a few case studies for example).  Our coatings offer an additional dimension in performance, be it analytical sulfur inertness, corrosion resistance, anti coking, or moisture resistance.  For the customer it means you don't have to take the time and effort to send in parts, just order them already coated from the manufacturer!  What can I buy?  Lots of things.  Here's list of components you can get directly from the OEM manufacturer. 

  • Fittings & Valves
  • Sample Cylinders
  • Process Sample Probes
  • Regulators & Flow Control
  • Filters & Separation
  • SST Tube, Tubing & Heat Trace
  • OEM & Instrumentation


The cost

Just do a Google search on the cost of placing and processing a PO and you'll see a wide range of estimates.  PO costs can range from about $60 per order to over $700 for some oil and gas applications.  That's just the administrative cost associated with order processing.  Now add in the handling cost at shipping and receiving and you're talking a fair amount of money invested in sending in a part for coating.  That's why it's worth a look into specifying our coatings when purchasing parts from the component or equipment manufacturer.  Depending on the OEM stock situation, the lead time may or may not be longer but from a cost perspective it'll be worth it to add our coating when specifying and purchasing the part.  Are you an OEM?  Become a partner and improve your products.

Become a Partner

The logistics

From a logistics and SKU perspective it also makes sense to consider purchasing coated parts.  A typical purchasing cycle can entail the following:

  • Specify coating
  • Source uncoated part or component.
  • Disassemble part
  • Place coating PO
  • Ship part to SilcoTek
  • Status order
  • Receive coated part from SilcoTek
  • Reassemble part
  • Process invoice

With good planning, the entire purchasing cycle can be eliminated by specifying our coating when placing an order for the uncoated part at the OEM level.  That will go a long way toward getting home a little earlier from work or greatly reduce the complexity of the order process!

Click here to go to our OEM partner directory.  The directory will take you to specific products and vendor purchasing information.

Want something that's not on our list?  Contact us and we'll do our best to work with your vendor to get us added as an option.

Tags: Oil & Gas Upstream & Downstream