We're a bleach manufacturer, and we've just acquired a facility with a floor that contains a metallic-aggregate surface hardener. We want to install a high-build epoxy coating on the floor to resist bleach spills. How should we prepare the floor for coating?
Because metallic-aggregate floors are so resistant to impact, it's difficult to mechanically roughen the surface to prepare it for coating. But Bob Cain of KRC Associates Inc. said that aggressive shotblasting, while not removing the metallic-aggregate cap, should roughen the floor enough to provide an adequate bonding surface. To achieve a rougher surface texture, Bob Gulyas of Master Builders Inc. recommended loading the shotblaster with steel grit instead of steel shot. Another approach was suggested by Jay Cullinan of Floortech. He says he has had success preparing metallic-aggregate floors with 20% phosphoric acid. Don't use hydrochloric (muriatic) acid because it will corrode the metallic surface. Before using any method on a large scale, it's always wise to prepare small sections of the floor, apply the coating, and perform adhesion tests as described in Appendix A of ACI 503R-93, "Use of Epoxy Compounds with Concrete."