I’ve been immersed (pun intended) in the coating industry for decades. I’ve installed, specified and inspected hundreds of different types of paint and coating systems. And I’ve heard the arguments for multiple-coat systems and single-coat systems. Clearly, in many cases, a multiple-coat system is intuitively the right choice. A perfect example is the standard tri-coat system for exterior surfaces, such as bridges, water towers, etc.: zinc-rich primer, intermediate epoxy tie coat and urethane topcoat. The primer is designed as a sacrificial system in the event that the two topcoats are compromised. The epoxy tie coat is strong, durable, scratch-resistant and has excellent adhesion and is not terribly costly. The urethane topcoat is designed to be UV resistant and color stable.
However, there are a number of excellent exterior coating systems that are designed to be applied in one or two coats of the same material. Whenever we can, we specify these single-coat systems over multiple coat systems.
We frequently provide our clients with what we term “optimal coating identification services.” We will search the marketplace and our organic knowledge of polymers to identify the best coating solutions for our client’s specific needs. Very often, when we solicit various coating manufacturer’s for their recommendations, they specify multi-coat systems. Often, each coat is a different product. Just recently, we performed an optimal coating identification for an international oil producer and we had three companies out of five provide us with multi-coat systems that used two or three different products.
Our concern here at Chicago Coatings Group is why. Is the reason purely technical, fact-based and in the best interest of the end-user? Or is it something else?
It is our view that with each coat, the likelihood of a coating failure doubles. Considering that 95% or more of all coating failures are due to application issues, why would anyone specify a multiple coat system if a single-coat system would do?
Consider the following facts:
- The more coats, the more money and profit the contractor makes.
- The more coats, the higher the cost to the client.
- Contractors may be incentivized to use products and systems that: a. will serve their client and b. increase their profit margin. This may lead some contractors to use, all things being equal, multiple coat systems over single coat systems.
- The more coats, the higher the likelihood of coating failure due to: a. exceeding recoat windows leading to intercoat delamination b. coating too soon, leading to solvent entrapment c. the possibility of amine blushing or other contaminants on a primer or base-coat prior to application of successive coats.
- Coating companies make more money when they specify multi-coat systems with different products. That is, with a predictive waste value of, say 15%, a coating company will sell more paint if they specify three different products (three different opportunities for waste) than if they specify a single coat system, or a multi-coat system with the same product.
Here at Chicago Coatings Group our single goal is to save our clients money. We believe that the choice between single coat and multiple coat systems should always be carefully evaluated before being specified and presented to a client.