I often get asked by my industrial and steel fabrication customers why some companies specify an epoxy topcoat and others specify a urethane topcoat. I'll get to that later in the article but what you need to know right now is that in regards to quality keep this in mind: a two-part urethane topcoat will almost always out perform a two-part epoxy topcoat.

First, almost all epoxies will chalk. This means after the fabricated metal product is completed and placed in the field part of the coating will rub off with anyone who comes in contact with it. For instance, if you have a large storage tank that employees climb up and down on all day they will be wearing this coating on their clothes at some point. Urethane coatings will not chalk and will retain their gloss & color much better. This usually translates in to much better overall protection in the long run.

Second, epoxies will yellow and discolor in outside environments. Although it is hard to say when this will happen exactly, it will happen at some point. Urethane coatings will again maintain their gloss & color much better.

If this is the case, why would anyone specify an epoxy topcoat rather than a urethane topcoat? The two most common answers are cost and production times. These theories revolve around the idea that epoxy coatings are cheaper on a per gallon cost basis and you are able to re-coat (your second coat) much faster resulting in increased production times. These theories are, however, mostly false. Here's why.

First, the cost on a quality urethane versus a high-performance epoxy should be very similar. If it is not than you need to negotiate with your paint vendor to get this done. Second, in regards to production times, there are some quality fast-drying production urethanes on the market right now. In some cases you can prime with a single component primer that can receive a urethane topcoat within thirty minutes to an hour.

There are also numerous self-priming urethanes and urethane-mastic coatings (an epoxy combined with a urethane in a single product). Ask yourself this the next time you select a paint system on steel. Why would you use a lesser quality coating system when you can use a superior paint system for the same price?