Frequently Asked Questions

Coating FAQs

Why do SilcoTek treated pieces have different colors?

The different colors of the coating can be attributed to angstrom-level thickness variations across the surface.  All SilcoTek coatings have a thickness of <1.5µm.

Certain coating processes (e.g. Silcolloy, SilcoGuard) result in a thicker layer and have a silver/matte gray appearance, while thinner coatings (e.g. SilcoNert) exhibit the ‘rainbow’ colors.



What are the temperature limits for SilcoTek treated surfaces?

In general, temperatures should not exceed the recommendations below in order to maintain the coatings' specified performance properties, but coated parts can be used at higher temperatures under certain conditions.  Heat treatment of parts at the application's temperature will ensure the best results if exceeding the temperature limits suggested below. Please contact technical support at 814-353-1778 or by clicking here for additional information or to discuss your application.

SilcoTek® coatings are stable to the following temperatures in an inert atmosphere:
*The values below reflect limits of the coating material itself and assume that the base substrate is stable at these temperatures.

SilcoNert® 2000 450 °C; 400 °C (oxidative atmosphere)
SilcoNert® 1000 720 °C
Silcolloy® 800 °C
SilcoGuard® 720 °C
SilcoKlean® 450 °C (functionalization loss), 400 °C (oxidative atmosphere)
Dursan® 500 °C; 450 °C (oxidative atmosphere)
Dursox® 500 °C
Notak® 300 °C


How thick are SilcoTek coatings?

There are several variables that determine thickness, but all SilcoTek coatings in current production are deposited at < 3µm thicknesses.  Please contact us to discuss thickness specifications.

Will the coating process affect the mechanical properties of stainless steel?

A metallurgical testing comparison of tensile strength, impact resistance and hardness on untreated 316 stainless steel, Dursan coated 316 stainless, and 316 stainless exposed to the Dursan heat profile under a nitrogen atmosphere revealed no significant change between all three test samples. 

Read the Technical Insight to get comparative data and test information. 

Ordering FAQs

Where can I order parts already coated by SilcoTek?

SilcoTek does not sell anything besides our coating services, but our Channel Partners work with us to stock their products with our coatings to help your supply chain.   Click here to see product listings.

How can I receive pricing for custom surface treatment?

Click here to request a quotation for custom surface deactivation of sample pathway components, inlet liners, etc. Please forward a scaled drawing or photograph detailing the product to be treated. Upon receipt of this completed worksheet, SilcoTek's Technical Staff will contact you with a quotation, typically within 1 business day or less.

When you are ready to send items to SilcoTek for treatment, contact technical support at 814-353-1778 or email to request a sales order number.

When submitting parts for treatment, remember that parts must be completely dissembled, and components that cannot withstand the high (400°C) temperatures associated with the process (rubber o-rings, brass, etc.) must be removed. Note that SilcoTek cannot assume liability for damaged parts due to process heat.

See your quote for specific disclaimers.

How do I select the most appropriate treatment for my application?

You can go to our product selector to find a coating for your application.

Go to Our Coating Selector Guide

Or you can go to our coatings page to learn more about our coatings.  The following definitions explain the various treatments currently available and their recommended applications:

  • SilcoNert® 1000 (Silcosteel®)
    A general-purpose passivation layer for steel and stainless steel.

  • SilcoNert® 2000 (Siltek®/Sulfinert®)
    The ultimate passivation of treated surfaces, from glass to high nickel alloys of steel. A required treatment for metal components when analyzing for parts-per-billion levels of organo-sulfur compounds, mercury, and other reactive chemicals.

  • Silcolloy® 
    A corrosion resistant layer that increases the lifetime of system components in acidic environments containing hydrochloric acid, nitric acid, or seawater.  Also a tremendous oxidation-resistant barrier.

  • SilcoKlean® 
    Dramatically reduces carbon coke buildup on stainless steel components.

  • SilcoGuard® 
    Greatly reduces outgassing from components of ultra-high vacuum systems.

  • Dursan®  
    Our most versatile coating.  Ideal for corrosion resistance in pH 0-14 environments but also highly inert for low-level (ppm) sampling.  Ideal for harsh processing or analytical environments, Dursan also offers 2x the wear resistance of bare 316 stainless steel.

  • Dursox®
    A ceramic-like silicon oxide (SiO) film.  Ideal for protecting parts when the carbon content of Dursan is not desirable.  
  • Notak®
        Improve surface repelling properties to resist build-up of water, oils, hydrocarbons, and foulants.

General FAQs

Does SilcoTek offer FDA compliant coatings?

Yes! Our Dursan® coating is certified by NSF International and therefore FDA compliant. However, most people ask about "FDA approval," and that question needs a more thorough explanation:

The United States Food and Drug administration (FDA) does not formally "approve" coatings or other materials for food or bio/pharmaceutical contact. Rather, the FDA regulates coatings via the Code of Federal Regulations (CFR), specifically 21 CFR 175.300 which lists what raw materials are acceptable and unacceptable for the formulation of coatings. It is then up to the coating supplier to self-regulate to ensure that they are using raw materials that are acceptable.

According to the FDA, a coating must 1) pass the solvent extraction tests listed in 21 CFR 175.300, 2) contain no heavy metals, and 3) all coating components conform to the materials listed by the FDA in order to be compliant. Since these stipulations are also required for NSF/ANSI 51 certification and Dursan successfully meets these requirements, our coating is FDA compliant. With respect to pharmaceutical applications, our data suggest that Dursan® does not "alter the safety, identity, strength, quality, or purity of the drug product beyond the official or other established requirements" per 21 CFR 211.65.

Nevertheless, we strongly encourage customers to test the use of Dursan® in their specific application to verify that performance requirements are met and the customer's production processes and outputs can continue to meet FDA approval guidelines.

Are SilcoTek's coatings RoHS and REACH compliant? What about their MSDS sheets?

Visit to learn more about how our coatings are non-hazardous and in compliance with the law.  The treatments do not require SDS sheets.

Can SilcoTek coat assemblies like valves, regulators, and flow controllers?


Regulator_DursanSilcoTek can coat the internal and external metal pathways for most flow regulating and metering devices to enhance their inertness and provide corrosion resistance. In order to coat the surfaces, all valves, regulators, and flow meters should be dissembled and all seals or parts which cannot be exposed to temperatures of approximately 400°C must be removed.

Disassembly should only be performed by qualified personnel with the appropriate seal kits, tools, and training OR damage or failure to the device will occur. For these reasons, SilcoTek cannot take on the responsibility of disassembly or reassembly of any valve, regulator, or flow meter.

If you do not have the experience and parts necessary to dissemble these devices, we recommend that you get in touch with Swagelok, Parker, or your valve manufacturer and order the coating treatment directly from them.

SilcoTek has business relationships with most manufacturers and routinely coats the internal and external surfaces of valves, regulators, and flow meters for them. The manufacturer will send the parts prior to assembling to SilcoTek for coating and will assemble the parts at their factory under the guidance of their quality systems.

Do I need to pre-clean my parts prior to sending them to SilcoTek® for coating?


SilcoTek uses a variety of precision surface preparation techniques to ensure parts receive the highest quality coating.   Additional pre-cleaning by the customer is often unnecessary and at times can be detrimental to our coating process.

In order to provide the highest quality coating and fastest processing; notify SilcoTek of any prior chemical exposure (regardless of whether the part is new or used).

Chemicals like cutting oils, pickling acids, solvents, water based cleaning compounds or other hazardous or non hazardous chemicals may impact the coating process. Many times the customer's cleaning process or chemical exposure can be eliminated, saving the customer time and money.

Will SilcoTek coatings make my non-compliant parts compliant with NACE MRO175 / ISO 15156?

No.  Raw, uncoated parts must be specified such that the material meets NACE MRO175 / ISO 15156 standards when they are ordered from the manufacturer.  Coating parts that are not already compliant with nace MRO175 / ISO 15156 will not make them compliant under any circumstances.

However, if SilcoTek coats parts that are already compliant with NACE MR0175 / ISO 15156, then they will remain compliant after coating - we simply added onto the already-compliant material.

What is SilcoNert 2000?

SilcoNert® 2000 (U.S. patent 6,444,326) is a passivation process that applies an inert, integral layer to components used for chromatographic analysis. Unlike traditional deactivations, it is not susceptible to cleavage or formation of active silanols and, therefore, greatly reduces bleed, and breakdown or adsorption of active components, compared to conventional surface coatings.

Are there byproducts as a result of the SilcoTek coating process that I should be aware of?

SilcoTek’s chemical vapor deposition (CVD) process produces coatings that are deemed “high purity” in most applications, including chromatography, medical diagnostics, and more.  However, the single byproduct of our silicon coating process is silicon particles (dust), which may be unacceptable in certain ultra-high purity applications e.g. semiconductor.  

Despite the use of best practices aimed to remove silicon particles after the coating process or to prevent them from forming in the first place, we suggest that customers who use their SilcoTek-coated parts in ultra-high purity applications conduct particulate testing to determine if the coated parts meet their specific cleanliness requirements.  If they do not, please contact us so we can assist in finding a 3rd party cleaning vendor who can provide a cleanroom-grade final coated product.

What are the part size limitations for SilcoTek coatings?

SilcoTek® can coat most parts including intricate precision components.  SilcoTek currently coats all parts at our facility in Bellefonte, PA which will require parts to be shipped to our facility and processed within a coating deposition process oven with a maximum size of 7'0" long x 5'0" wide x 7'6'' high.  Our technology is able to coat very intricate geometries used for precision components and is scalable to much larger sizes. Our current capabilities are outlined in the summary below and our team is always willing to discuss the possibilities of your application, even if it may seem outside our current dimensions.  Please contact our team to discuss possibilities for your application.


Part Size

  • Largest overall part size: 2.032m x .76m ID (80in x 29.92in ID)   Note: Size may be larger, contact our Technical Service Team to discuss your application.
  • Smallest part size: Approximately 1mm (0.039in).  Contact us to discuss your application.

Tubing Capabilities

SilcoTek® offers two processes for coating tubes:

Coiled/Rolled Tubing  Coiled Tubing

  • Coated internally-only 
  • Maximum continuous length: 
tubing size summary 2
  • Maximum coil OD for tubing > 1/16" OD: 36"
  • Maximum coil OD for tubing 1/16" OD or smaller: 18"
  • Must be shipped on a metal spool or bound with metal wire.  No spools made of wood, plastic, or other flammable materials.

Straight Tubing Sticks  Straight Tubes

  • We're adding capacity to our tubing coating process!  We'll soon have the capability to coat straight tubing sticks up to 24 feet long.  Contact our Technical Service Team to learn more.

Our current straight tube capability:

  • Coated both internally and externally
  • Maximum length: 80"

Dursan Tubing Limitations

Design, Fabrication and Installation of Coated Parts

Can I weld my parts after coating?

Welding will remove the SilcoTek coating ~2-4mm in all directions from the heat affected zone.  SilcoTek can coat over high-quality welds, such as those listed in our material compatibility guide.  For specific questions regarding welding, please call +1 (814) 353-1778 and press 2 for technical service.

What are my options for coating tubing?

SilcoTek offers two processes for coating tubes:

Coiled/Rolled Tubing  Coiled Tubing

  • Coated internally-only 
  • Maximum continuous length, see table below: 
Max coil length table (003)
Other tubing requirements:
  • Maximum coil OD for tubing > 1/16" OD: 36"
  • Maximum coil OD for tubing 1/16" OD or smaller: 18"
  • Must be shipped on a metal spool or bound with metal wire.  No spools made of wood, plastic, or other flammable materials.

Straight Tubing Sticks  Straight Tubes

  • Coated both internally and externally
  • Maximum length: 80"

Will brazing or soldering impact the quality of the coating?

Click here to read a Technical Insight from SilcoTek's R&D group regarding coating of brazed and soldered components.

We recommend vacuum brazing or welding of joints for best coating quality. Vacuum brazing is a high temperature, flux-free brazing process that results in a contamination-free joint. SilcoTek recommends vacuum brazing services from Solar Atmospheres Inc.

Do SilcoTek coatings change the roughness of the surface?

SilcoTek coatings conform to the microstructure of the part surface.  There is minimal filling of voids or change to the overall surface roughness.  Overall roughness measurement may be reduced slightly (1-2 RA reduction), but not a significant change in roughness.  Some SilcoTek coatings have a higher lubricity than stainless steel, so even though surface roughness has not changed, the surface may have a lower friction coefficient.

Can sealing surfaces be coated?

Yes!  SilcoTek coatings are proven to withstand compression and shear stress common to CF, face seal, and threaded sealing systems.

For more information about SilcoTek coatings and sealing surfaces, click here!

FSEM ImagePre_sealed_surface_2_8_10_15_2

FESEM (Field Emission Scanning Electron Microscopy) image of the coated pre-sealed surface shows the coating conforms to the sealing area.  The raised surfaces of the face seal gland area can be seen.  SilcoTek coatings conform to surface contours and small orifices.


FSEM Post_seal_1_8_10_15

After making the metal-to-metal face seal per manufacturers instruction, a second FESEM image of the post sealing surface shows no scarring or scratching, only trace particulate from the silver gasket.

Can ferrules be treated?

SilcoTek does not recommend coating ferrules as we have found this may lead to leaking problems after coating.

Coating non-Steel Substrates

What materials can be surface treated? What can you coat?

Virtually all alloys of stainless steel, ceramic, and most glass materials can be treated. Some other metallic materials, such as nickel, brass, and copper, are incompatible with the 400+°C temperatures used in the process, and should not be treated. 

Note: carbon steel, F22 or similar carbon steel, is not recommended for coating in corrosion resistant applications.  Treated carbon steel may rust in corrosive environments.  Avoid corrosive environments when using treated carbon steel in inert sampling applications.

SilcoTek can coat aluminum substrates however there are limitations for components used in high stress applications.  Go to our aluminum coating page to learn more about aluminum coating capabilities.  Contact us to ensure optimal processing of your aluminum parts.

Will you re-deactivate my SilcoNert® 2000 treated glass liners or SilcoNert® 1000 metal liners after I clean them?

Request re-deactivation of SilcoNert 2000 treated glass liners by contacting SilcoTek's Customer Service department at 814-353-1778. Requesting SilcoNert 2000 re-deactivation of customer supplied liners. A minimum of ten liners is required. Metal inlet liners are designed as inexpensive, disposable products and it is not cost effective to re-treat them. We recommend discarding them when they are no longer serviceable.

What is the maximum temperature limit for SilcoNert 2000 deactivated glass?

Maximum temperatures usually will be dictated by the composition of the glass, not by the surface treatment. The SilcoNert 2000 layer is stable at temperatures up to 400°C, but some glasses can soften at lower temperatures. Injection port temperatures normally are well below the SilcoNert 2000 maximum temperature limit, so SilcoNert 2000 treatment is an excellent deactivation for all injection port surfaces.

Why is SilcoNert® 2000 on glass gold in color?


The color of a surface coating is an expression of the light diffraction qualities and thickness of the layer. The thickness of a SilcoNert 2000 layer determines the degree of darkness, secondary reflectivity, and/or final color of the item. The color can range from light golden-brown (thin coatings) to reflective silver (heavier coatings). We deposit a layer that provides a gold color on liners to aid analysts in inspecting for cleanliness. Chromatographic performance does not depend on the thickness of the layer.

Can SilcoTek® coat fritted liners?

SPECIAL NOTE: Coating of glass fritted liners - SilcoTek would prefer that all glass liners be sent without deactivation (e.g. silanization) since the deactivation layer will prevent our intermolecular coatings from bonding to the surface. For most glass liners, our cleaning process will remove all prior deactivants. However, SilcoTek cannot put fritted liners through our cleaning process without damaging the frit.

Fritted liners are special because there is no effective way of cleaning glass frits or stripping the coating in case of failure. As we continue to gain experience with glass frits and tailor our processes, we will get better. Our major hurdle is being able to "test" fritted liners prior to coating to ensure they are clean. We continue to work on this aspect of our operation.

Can SilcoTek coat aluminum substrates?

Yes, SilcoTek can coat most grades of aluminum alloys.  If possible it is recommended that customers inform SilcoTek of the material grade of aluminum substrates prior to sending parts. Learn more by clicking here to go to our Aluminum Coating Page

*SilcoTek does not recommend coating cylinders or any other aluminum product that will be pressurized or used in high stress applications.

Corrosion Applications

How long will a SilcoTek coating last in my corrosive application?

We recommend all end users test SilcoTek coatings in corrosive applications to better understand the performance and potential lifetime prior to installing coated parts into service.  Since every corrosive application is different, several factors impact the coating's lifetime, and there are potential risks associated with failure, it is nearly impossible for us to provide a realistic estimation.

Our goal at SilcoTek is to partner with you to help you solve your corrosion problems, so we put a priority on helping you evaluate our coatings.  This includes gathering relevant test data, providing samples, coating your test pieces, and putting our technical experts on your project to find a solution that works.  Please contact us to discuss your application and establish a testing and validation plan.

How will SilcoTek surface treatments work in my acidic environment?

SilcoNert 1000 and SilcoNert 2000 treated materials have improved corrosion resistance, but Silcolloy (formerly Silcosteel®-CR) and Dursan surface treatments are optimized to enhance resistance to many common acids; providing a 10-fold improvement in corrosion resistance, compared to untreated stainless steel, and a 4-fold improvement compared to SilcoNert 1000 coated stainless steel.

Note: carbon steel, F22 or similar carbon steel, is not recommended for coating in corrosion resistant applications.  Treated carbon steel may rust in corrosive environments.  Avoid corrosive environments when using treated carbon steel in inert sampling applications.


Why does the exterior surface of internally-coated tubing sometimes look different from coil to coil?

Tubing coils 10 10 18

SilcoTek’s process for treating coiled tubing results in a uniform coating throughout the interior of the tubing from end to end.  The exterior surface of coiled tubing is not coated, but it will exhibit a change in appearance after being oxidized by the high temperatures of our CVD coating process.  This resulting external appearance will vary based on the specific elemental composition of the tubing substrate. 

What is the maximum length of tubing you can coat?

SilcoTek offers two processes for coating tubes:

Coiled/Rolled Tubing  Coiled Tubing

  • Coated internally-only 
  • Maximum continuous length, see table below: 
tubing size summary 2
Other tubing requirements:
  • Maximum coil OD for tubing > 1/16" OD: 36"
  • Maximum coil OD for tubing 1/16" OD or smaller: 18"
  • Must be shipped on a metal spool or bound with metal wire.  No spools made of wood, plastic, or other flammable materials.

Straight Tubing Sticks  Straight Tubes

    • We're adding capacity to our tubing coating process!  We'll soon have the capability to coat straight tubing sticks up to 24 feet long.  Contact our Technical Service Team to learn more.

    Our current straight tube capability:

    • Coated both internally and externally
    • Maximum length: 80"

How tightly can the tubing be bent?

Our recommended minimum bend radius is calculated by multiplying the tube OD by 16. This is a common surface finishing guideline that is conservative to ensure tubing is not stretched to the extent of exposing new, uncoated surface area.


<= 1/16"






Min. Bend Radius

1" (2.5 cm)

2" (5.1 cm)

4" (10.2 cm)

6" (15.2 cm)

8" (20.3 cm)

12" (30.5 cm)


In many applications, coated tubing can be bent tighter than the above guidelines without degrading performance. Click below for our tubing application brief. 

See More Data and Learn More

Will SilcoTek coatings adequately coat the inside of very small diameter channels and tubing?

Yes!  Our unique chemical vapor deposition process is performed in the gas phase, so even the smallest channels and tightest tolerances will be adequately coated along with the rest of the part.  We also have the ability to coat certain tube configurations internally-only.

We proved this by coating a 1/16" OD, .4mm ID tube with multiple bends both internally and externally.  After coating, the tube was cut open to examine the coating at the center-most point inside the tube.  In addition to the external coating on the tube, a quick visual inspection shows the vibrant purple-colored SilcoTek coating inside the narrow bore.  



The thickness of the coating throughout the tube was verified by aFilmetrics F40-Series Thin Film Analyzer and it was confirmed to meet our specifications.  SilcoTek coatings are not applied with line-of-sight processes that lead to inconsistent deposition and uncoated areas.  With our process, 100% of your parts are coated, even if the design is complex or the pathways are tortuous.