It can sometimes feel as though we are programmed to think that bigger is better and the more features you have the better a product is. But is that also the case for paint coating systems? We strip back the layers on this topic below to reveal what the differences between 2-coat and 3-coat Kynar PVDF paint systems really mean and share some tips that might assist with future specifications.
However, before we start we want to briefly touch on the 4-coat paint system. You may not be as familiar with 4-coat paint systems as they are older and advances in technology have made them almost obsolete. Therefore, our blog post focuses on the more common 2-coat and 3-coat pain systems.
If you don’t have time to read this article, here is the conclusion: Leave the decision on whether a finish should be 2 coat or 3 coat to the product manufacturer.
To understand why that is the conclusion, read on:
What are the layers in a 2 coat and 3 coat Kynar 500 PVDF finish?
After the base metal is cleaned and pretreated, it goes through 2 or 3 coating processes depending on the requirements of the finish:
1. Primer: this is a very important step to ensure the quality and longevity of the finished product.
2. Finish Coat: this is where the color is applied
3. Top Coat: when a finish requires a third layer, it receives a top coat, typically a clear or tinted clear coat.
NOTE: A 3-coat is NOT 2 layers of the Finish Coat!
What’s the difference between 2-coat and 3-coat PVDF paint systems?
This may seem obvious but basically, the difference is that one paint system consists of two layers whereas the other system has three layers. Typically, two-coat paint systems include a primer and a topcoat while three-coat paint systems also include a primer and a topcoat and then a third coating layer (typically a clear coat) that is applied last.
In metal coatings, it is important to note that the third coat is not just another layer of the second coat. It is not the same as painting your living room wall, where you step back and say “lets give it another coat to make sure there is even coverage”. Instead, the third coat is used for a specific purpose when the finish requires it.
When is a 3-coat finish required on coated metal?
Here are some examples of when paint manufacturers and coaters may develop a finish with 3 coats instead of 2 coats:
1. Metallic finishes that use aluminum flakes need a clear coat to protect the delicate flakes. In contrast, metallic finishes that use mica flakes – which are a hard stone material – do not need a third coat to protect the mica flakes. Always leave the decision of 2 coat or 3 coat, mica or metallic flake to the manufacturer!
2. Some finishes need a higher gloss level than can be achieved in the same coating that is producing the color. For example, the base and pigments needed to achieve a specific color may not also be able to achieve the desired gloss level. Therefore the combination of the second and third coat achieve both the color and the gloss level desired.
3. Patterned finishes have a base color, one or more ink layers, and then may require a clear coat to protect the ink.
Should I specify a 2-coat or a 3-coat finish on metal cladding?
The simple answer is NO – contrary to traditional opinion, the decision on whether a finish has 2 or 3 coats should be left up to the product manufacturer. Some finishes require 2 coats and some require 3 coats. Adding a 3rd layer to a 2-coat finish may alter the color and gloss level, and may even reduce the warranty, because the top-coat is not simply an additional layer of the 2nd coat, but rather a clear coat that may not be as UV resistant as the 2nd coat.
Instead, specify performance and quality requirements, like warranty, fade resistance, etc… referencing the AAMA 2605 standards.
Ordering Samples
Should you order a lab sample in both 2-coat and 3-coat to compare? We don’t recommend this. Both lab samples will look identical, and these lab samples are for visual purposes, not for technical evaluation. However there are times when matching a finish, it can only by matched in either the 2 or 3 coat finish, but not both. We recommend that you leave the decision on whether to have a 2-Coat or a 3-Coat to the experts at Fairview who know the application and understand the coating processes and how coloring and longevity are affected by the option of 2 or 3 coat paint systems.
Contact us to tell us about your custom color project and to request samples!
Cost
It is inevitable that cost must come into the equation as the additional time and materials of 3-coat finishes will cost more. Also, if the third coat requires running the material through the coating line again, there will be additional waste and scrap that must be accounted for. However, there are other factors that go into pricing, so it is always best to get a quote to see which coating is better suited to your budget. For example, to add a third coat onto a standard 2-coat finish will be treated as a custom color, and therefore be more expensive than a standard 3-coat finish. As always, it is advisable to leave the decision on whether a finish should be 2-coat or 3-coat to the experts.
Warranties
To address the issue of coating performance, let’s look at warranties. Many don’t realize this, but the three-coat paint systems with the extra layer of protection may not have a longer warranty than the 2-coat systems. This is because the decision on whether to have a 3-coat system or 2-coat system is about the finish itself. Also, the stability and quality of a third coat may actually be inferior to that of the second coat, meaning that in some cases a longer warranty can be achieved with a 2-coat system than a 3-coat system. This is another reason to specify the warranty length, and not the number of coats.
Specifying a Coating System
There is an art to writing specifications to guarantee that you get what you want and avoid any post-bid up charges if there are areas that are open to interpretation. As a suggestion, we recommend including the term, “manufacturers full standard colors including solid and metallic finishes”, in your specifications. Instead of specifying that it must be a 3 coat or a 2 coat finish, we recommend that you specify an AAMA 2605 PVDF continuous coated finish, and not a spray applied finish. Not all finishes can achieve the warranty you may need, therefore we recommend you speak to a Fairview representative to choose finish that will look beautiful for years to come!
Final thoughts
In summary, the decision between a two-coat vs. three-coat paint system should be left to the product manufacturer. This should then be considered against other factors such as the project budget and construction schedule as part of the decision-making process. If you are still unsure of what is the best solution, we are here to help. Simply contact our team for a chat here.