People use barrier coatings to improve the performance of their products.  For example, coatings can improve corrosion resistance, make surfaces inert, reduce product contamination, or for improve non-stick performance.  But what about coating pitfalls?

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Barrier Coating Benefits and Pitfalls

Coatings are used to economically improve the performance of the base material, product or process.  Using the right coating for the right application is key to avoiding coating problems.  In this blog we discuss coating benefits and pitfalls.  

In this blog post you will learn:

• Key benefits and takeaways from using barrier coatings in a variety of applications.
• We'll discuss some potential pitfalls relating to the use of barrier coatings and how to avoid future coating performance problems.
• How to pick the right CVD coating for your application

CVD Coating Benefits

Not all coatings work for all applications.  For example an acrylic coating may be an economical corrosion fighter in some applications, but try and use that coating in an abrasive environment or in an application where a non reactive surface is needed and the results will be disappointing.  In the examples below we'll discuss the benefits of silicon coatings applied by chemical vapor deposition.  Polymeric coatings or metallic coatings will perform differently, so be sure to evaluate the coating in the application before use.

Corrosion resistance

Barrier coatings protect critical surfaces from corrosion and contamination, improving component durability and process yield.  Benefits include:

• Improved corrosion resistance
• Less metal ion contamination
• Outstanding moisture control

The comparison below highlights the improved corrosion performance of CVD barrier coatings.  Coated surfaces offer a 10x or greater improvement in corrosion resistance without changing the product material or design.

Inertness

Coatings, like SilcoNert® improve lab and instrument performance by creating a chemically inert flow path which prevents sample adsorption and reactivity.  Benefits include: fast response, improved sensitivity, low distortion, reduced carryover and contamination.  Comparative testing (below) of reactive organochloride and organochlorine show significant improvement of inertness over polymeric coating deactivation.  

Hydrophobicity

SilcoTek's inert high temperature barrier coatings enhance hydrophobic performance of critical flow path surfaces.  Dursan®coating improves moisture repelling properties of stainless steel, glass, and ceramic surfaces by 60% or more, minimizing wetted surface effects.

Water droplet contact angle measurement (below) shows a significant improvement in water repelling properties.  Coatings that repel water can improve corrosion resistance and help manage moisture in processes sensitive to water contamination.

Non-stick fouling resistance and mold release

Low surface energy silicon CVD coatings reduce surface friction and stiction, and improve carbon coking and fouling resistance.  Coatings can help improve engine efficiency, reduce maintenance and improve plastic mold release and durability.  Fouling tests (below) show significant improvement in carbon coking resistance when using silicon coatings.

Barrier Coating Pitfalls

Barrier coatings offer many benefits but can also present some significant challenges.  Poor coating selection, improper surface preparation, or substrate compatibility issues can lead to coating failures and performance issues.  Let's discuss some common coating pitfalls.

Pinholes or coating breaches

Pinholes or small point source channels can result from surface contamination during the coating process or as a result of outgassing when applying a coating.  Channels or breaches can act as a conduit for cathodic reactions which can result in concentrated corrosive attack at the pinhole.  Coatings that are electrically conductive and support cathodic reactions, oxygen reductions or hydrogen evolution are more likely to promote a cathodic reaction and localized corrosion.  Avoid conductive polymers and noble metals (ie. copper, silver, gold) as a barrier coating for corrosion applications when protecting more active metals like aluminum or steel.  

Barrier coatings that are are not conductive or less conductive provide better cathodic protection and will reduce the potential of corrosive attack at voids, pinholes or breaches.  Proper surface preparation can also help to prevent pinholes.  The EIS corrosion resistance test below demonstrates how a properly applied coating can significantly improve corrosion resistance and minimize pinholes.  The CVD coated sample (blue lines below) show minimal current breakthrough, indicating minimal pinholes in the coating surface.

Coating adhesion problems

Surface contamination can result in poor bonding of a coating to the surface.  That can lead to adhesion problems and failure of the coating.  The coating comparison below shows how adhesion can vary significantly between coatings.  Paints can have significant adhesion issues because preparation of the underlying surface can vary.  Salts, particulates, grease of other contaminants can significantly impact adhesion.

Abrasion/wear

Polymeric and softer metals can lack abrasion and wear resistance.  In industrial applications this can lead to a loss of coating at the wear site.  Pin on disc wear testing, surface impact testing, or bend/stress testing can determine if the coating is appropriate for your application.   Compare coated samples to the base metal performance.  In the example below, an pin on disc test compared oxidized stainless steel to carboxysilane (Dursan) coated stainless steel.  In this test, the coating proved beneficial in the application and showed significant reduction in friction and wear rate.

Moisture interaction

Brush on or spray on coatings (i.e. organic coatings like epoxies, paints, acrylics) have some degree of water permeability.  They can absorb moisture and can be problematic in high humidity environments.  If the coating to surface interface is robust, that absorbed moisture won't lead to a corrosion problem but if the surface interface is poor (due to surface contamination), moisture can build up at the coating-substrate interface and cause blisters and coating failure.

Coating cracking

Oxide, nitride and carbide coatings are resistant to moisture but can lack the flexibility needed to remain intact under stress.  These coatings can crack or delaminate from the surface under extreme conditions.  Flex testing and impact testing help quantify how the coating will perform in the application.

Learn more about potential coating pitfalls by going to our Frequently Asked Questions page.  You'll come away with lots of CVD coating information.

CVD Coating Frequently Asked Questions

How SilcoTek coatings stack up?

Pinholes

Silcotek® coatings minimize pinhole effects through improved surface preparation techniques and rigorous process controls.  Silcotek's silicon CVD coatings demonstrate electrically neutral to insulative characteristics which minimize cathodic reactions in the event of a coating breach.

Adhesion

SilcoTek's proprietary surface preparation methods and rigorous process controls help to improve the quality of the bond between the coating and substrate.  This dramatically improves adhesion compared with other coatings. 

Abrasion/wear

Wear resistance testing shows SilcoTek coatings, like Dursan, show improved wear resistance compared to polymeric coatings.

Moisture resistance

Coatings like Dursan and Notak repel water.  This improves corrosion resistance and moisture management in systems sensitive to moisture contamination.

Selecting the Right Coating

Coating performance is one factor in a successful coating outcome but the most important factor is selecting the right coating for the application.  There are a vast number of coatings available so it's wise to research the coating before using it in your application.

For more water based barrier coatingsinformation, please contact us. We will provide professional answers.

Tips for Selecting the Right Coating

A successful coating solution involves matching the performance environment of both the application and the coating. Here are questions to consider and review with SilcoTek’s technical experts before making a coating selection.

1.  Chemical exposure and environment

• Is the application exposed to acids or bases?
• What target chemicals are you sampling?
• Duration of exposure
• Operating temperature
• Cleaning solvents and methods used
• Abrasives or other durability concerns
• Previous chemical exposure of the part

Why is this important?  

Because chemical exposure can be a source of pitting and surface damage that can lead to chemical adsorption and sample or product cross contamination.  Protecting the surface by applying a high durability, inert coating can improve performance but exposure can play a big part in overall life of the coating.  Sometimes we'll select a slightly less inert but more durable coating in order to strike a balance between performance, durability and coating life.

2. Form factor of the part

• What areas of the part are sensitive to damage?
• Surface finish of the part
• Wear points of the part
• Metallurgy of the part
• Where can the part be held with a handling fixture?
• Are there seals or o-rings in the part?
• Is the part disassembled?

Why is this important?

Because part metallurgy and surface finish can play a role in coating compatibility and adhesion.  We can apply coatings to most metals but there are some (like copper and copper alloys) that react negatively to silicon surface bonding.  This can result in poor coating morphology and reactivity.  Wear or damage sensitivity can dictate handling and coating selection.  We may fixture a part differently depending on the surface and we may select a more durable coating in wear applications.  O-rings and part assembly can severely impact coating quality, so we request the part be completely disassembled to assure quality.

3. Performance requirement of the part’s surface

• How do you need the surface to perform? Corrosion resistance, inertness, hydrophobic, etc.
• Are there welded or brazed/soldered joints in the component?
• Are there blind holes or small cavities in the part?
• Overall dimensions and quantity

Why is this important?

Desired performance is obvious.  We don't want to apply a coating that does not meet performance expectations, but we also want to know about the overall part configuration, it's precision and if there are small flow paths.  That's because we often specify special preparation, fixturing or processing for intricate or high precision parts.  

That’s a lot to consider! If you don’t know something about a part, our technical staff and production technicians will address any questions or potential issues. If you know lots about your part, you may feel comfortable selecting a coating and completing our online quote request form.

Go to our coating applications page to learn more about where SilcoTek® coatings solve material problems, or check out our webinar on selecting the right coating for your application.

THE PROS AND CONS OF VARIOUS WATER TANK COATING TYPES:

Choosing the right water tank coating is crucial for durability and cost-effectiveness. Here’s a comprehensive comparison to guide your decision.

Understanding Water Tank Coatings: The Basics

Water tank coatings play a critical role in safeguarding the tank from a variety of environmental factors, such as extreme weather conditions, moisture, and temperature fluctuations, which can all contribute to the deterioration of the tank's structure over time. Additionally, these coatings are vital in preventing corrosion, a common issue that can lead to leaks and structural failures, as well as contamination, which can compromise the quality and safety of the water stored within the tank. To achieve these protective benefits, coatings are applied to both the exterior and interior surfaces of the tanks. This dual application not only extends the lifespan of the tanks by providing a robust barrier against potential damage but also ensures that the water remains safe and uncontaminated for consumption or use.

Selecting the appropriate coating involves a careful evaluation of several factors. The material of the tank, whether it is made of steel, concrete, or another substance, can significantly influence the type of coating that will adhere best and provide optimal protection. The tank's location is another crucial consideration, as tanks situated in coastal areas, for example, may require coatings with enhanced resistance to saltwater corrosion. The type of water stored, whether it is potable, wastewater, or industrial water, also dictates the necessary chemical resistance and safety standards of the coating. Lastly, budget constraints can impact the choice, as some coatings may offer superior protection but at a higher cost. By gaining a comprehensive understanding of the basic types of coatings available, along with their respective advantages and disadvantages, individuals can make a well-informed decision that aligns with their specific needs and ensures the long-term durability and safety of their water tanks.

Exterior Coatings: Acyrlic vs. Polyurethane vs. Fluoropolymer

Acrylic coatings, like Tnemec Series Enduratone, are water-based and eco-friendly, making them an excellent choice for projects that prioritize environmental sustainability. These coatings are formulated to minimize the release of volatile organic compounds (VOCs), which can be harmful to both the environment and human health. This eco-friendly nature makes acrylics particularly appealing for use in areas with strict environmental regulations or for projects aiming to achieve green certification. Additionally, acrylic coatings are relatively easy to apply, requiring minimal specialized equipment or training, which can reduce labor costs and application time. They dry quickly, allowing for faster project completion and less downtime, which is beneficial in time-sensitive situations. However, despite these advantages, acrylics may not offer the same level of durability and resistance to harsh environmental conditions, such as extreme temperatures, UV exposure, or chemical contact, as polyurethanes. This limitation can result in a shorter lifespan for the coating, necessitating more frequent reapplications and potentially increasing long-term maintenance costs.

Polyurethanes, like Tnemec Series Endura-Shield, are renowned for their exceptional durability and flexibility, making them a versatile choice for a wide range of applications. These coatings form a robust protective layer that is capable of withstanding harsh weather conditions, such as heavy rain, snow, and intense sunlight, which can otherwise cause significant wear and tear on exposed surfaces. Additionally, polyurethanes are highly resistant to abrasion, meaning they can endure physical impacts and friction without easily wearing down. This makes them particularly suitable for environments where surfaces are subject to frequent contact or movement. Another advantage of polyurethanes is their relative cost-effectiveness. They offer a balance between performance and affordability, which makes them a popular choice for many projects, especially those with budget constraints. However, it is important to note that the life cycle of polyurethane coatings can be shorter compared to fluoropolymers, particularly in extremely harsh environments .

Fluoropolymers, like Tnemec Series 701 Hydroflon, on the other hand, are distinguished by their superior longevity and remarkable resistance to a variety of environmental stressors. These coatings excel in protecting surfaces from UV radiation, which can cause fading and degradation over time, as well as from harsh chemicals and high temperatures that might otherwise compromise the integrity of the coating. While fluoropolymers tend to be more expensive than polyurethanes, their extended life cycle often justifies the higher initial cost. This is because they require less frequent reapplication and maintenance and stay cleaner longer, ultimately leading to cost savings over the long term. Fluoropolymers are an excellent choice for projects where long-term durability and minimal maintenance are priorities, such as in industrial settings or in locations with extreme environmental conditions. Their ability to maintain their protective properties over extended periods makes them a reliable option for ensuring the longevity and safety of the surfaces they cover.

Interior Coatings: Epoxies vs. Hybrid Urethanes

Epoxy coatings, like Tnemec Series 21 or Series 22, are widely used for interior water tank applications due to their excellent adhesion, chemical resistance, and durability. These coatings are formulated to create a hard, protective layer that adheres strongly to the tank's surface, effectively preventing corrosion and contamination by forming a barrier against water and other potentially harmful substances. This makes them particularly suitable for environments where the water quality must be maintained at a high standard, such as in potable water tanks. However, despite their many advantages, epoxies can be brittle and may not perform well under conditions of thermal or mechanical stress. This brittleness can lead to cracking or delamination when the tank is subjected to significant temperature fluctuations or physical impacts, potentially compromising the protective barrier and necessitating repairs or reapplications.

Hybrid urethanes provide flexibility, durability, and resistance to chemicals. These coatings are designed to endure a broader range of conditions, reducing the likelihood of cracking or peeling under stress. However, they tend to be more costly than traditional epoxy coatings, which can be a financial burden, particularly for large-scale projects. Furthermore, their effectiveness can fluctuate with environmental conditions, and they often require specific application methods and a plural component application to ensure proper adhesion and performance. If not applied correctly, they will not offer the same level of performance as other coatings, potentially affecting water quality.

Making the Right Choice for Your Water Tank

Choosing the right coating for your water tank is a multifaceted decision that requires careful consideration of various factors to ensure optimal performance and protection. First and foremost, you must evaluate the specific requirements of your project, which may include the type of water being stored, the material of the tank, and the intended use of the water. For instance, potable water tanks may necessitate coatings that meet stringent health and safety standards, while tanks used for industrial purposes might require coatings with enhanced chemical resistance.

Environmental conditions play a significant role in determining the appropriate coating. Factors such as temperature fluctuations, humidity levels, and exposure to UV radiation or saltwater can all impact the performance and longevity of a coating. Tanks located in coastal areas, for example, may benefit from coatings with superior resistance to saltwater corrosion, while those in regions with extreme temperatures might require coatings that can withstand thermal stress.

Budget is another critical consideration, as it can influence the choice of coating based on initial costs and long-term financial implications. While some coatings may be more expensive upfront, their durability and reduced maintenance needs can lead to cost savings over time. Conversely, more affordable coatings might require frequent reapplications, potentially increasing long-term expenses.

Long-term maintenance needs should also be factored into the decision-making process. Coatings that offer extended lifespans and require minimal upkeep can reduce downtime and maintenance costs, ensuring that the tank remains in optimal condition for years to come.

Understanding the pros and cons of each coating type is essential for making an informed decision that ensures the durability and safety of your water tank. Each coating has its unique advantages and limitations, and selecting the right one involves balancing these factors to meet your specific needs.

Our expertise in water tank coatings can provide valuable insights and guidance. We can help conduct a thorough assessment of your tank's needs, taking into account all relevant factors, and recommend the most suitable coating options. Whether you prioritize cost, longevity, environmental impact, or a combination of these factors, there is a coating option available that can meet your requirements and provide optimal protection for your water tank. By trusting us to carefully evaluate all these aspects, you can ensure that your water tank will remain durable, safe, and efficient in its operation.  

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