In this month’s technical tip, we are going to look at how to minimize or eliminate outgassing bubbles that may appear in the coating surface after a 100% solid’s coating is applied over a porous concrete surface.
Outgassing bubbles may appear in the coating surface after a 100% solid’s coating is applied over a porous concrete surface. This condition is created when the coating begins to heat up (exotherm) during the curing process. As the coating increases in temperature, cooler entrapped air in the substrate expands and rises into the coating, thereby creating bubbles. The problem is not with the coating, but with the surrounding conditions associated with temperature, expansion and capillary action.
1.) To aid in the elimination of the “outgassing” problem, don’t apply coatings in extreme heat or in direct sunlight. Apply your coatings when the substrate and ambient temperatures are similar. This will help to reduce the chance of outgassing bubbles.
2.) Priming highly porous concrete with a thinner coat of water-based material, 4001 or 4010 @ 250 sq. ft. per mixed gallon will greatly reduce outgassing. (The water molecules expand less then air when warmed).
3.) Priming with MVT 100% solids epoxies 4195, 4100 and 4150 if outgassing is evident during the application. Walk out onto the wet surface wearing spiked shoes and spray a light coat of acetone to pop the bubbles out. It may possibly require a second primer coat with sanding to correct any blemishes, bubbles or pinholes caused by the elevated rate of moisture vapor transmission releasing through the substrate.
Questions? Contact Jeff Blakney, Sales/Technical Support, at (714) 829-2522