Epoxy Swimming Pool Paint

Question:

I am the design manager for my company. We are working at producing a set of water tables for a children’s exhibit and are finding trouble applying a coating to these tables. The customer wants the tables painted blue and so we settled on a blue two-part epoxy coating that has some texture. It was applied onto a roughed up surface that was washed according to instructions.

Once the tables were ready for trials, we filled them with regular, city treated, tap water and ran the trials. When the water was removed the coating began to crack and break up like a dry riverbed, but only where the product had been submerged. Where the product was mostly dry it seems perfect, very hard to remove or even damaged.

This epoxy product is sold as pool paint, which we thought should perform well enough but apparently didn’t. Can you recommend a brand or manufacturer of product that would suit this application? G. D.

Answer:

Although all swimming pool paints are not created equal, they are all, by definition, water-resistant. Furthermore two-component epoxy paints are noted for this property and are also used extensively as tank linings. I do not recommend specific brand names and product suppliers in the Painting Clinic.

The phenomenon you described used to be called mud cracking and occurred with uneven drying of oleoresinous and long-oil modified alkyd paint films. Although I haven’t seen this in epoxy paint films, I can think of a couple reasons why it happened. If the epoxy paint film was not fully cured before the water tables were filled, water could leach out water soluble components of the film. If the epoxy components were not mixed in the correct proportions, the film would not fully cure and the same thing would happen. It is important to note that although two-component epoxy films will “dry” rather quickly, they may not be fully cured for several days and are therefore not ready for service conditions. You must follow the supplier’s recommendations to thoroughly mix the components in the correct proportions when using these materials.