It is known to provide a corrosion resistant synthetic resin coating on a concrete structure by applying a curable synthetic resin to the surface of the concrete, e.g. a concrete waste water tank.
The surface to be coated is subjected to a cleaning treatment, and the synthetic resin is applied to the cleaned surface to form the corrosion resistant coating.
The cleaning treatment can be accomplished by steps such as sand blasting, steam cleaning, the use of pressurized water jets, flame cleaning and by abrading process.
The synthetic resin or plastic typically comprises a polyester resin, an epoxide resin, a polyurethane resin, an acrylic resin, or the like. Preferably a polyester resin is used. One can apply the synthetic resin or plastic directly to the cleaned surface, for example by spraying. The corrosion resistant synthetic plastic resin coating can also be formed by rolling it or troweling it onto the surface.
Both thick and thin corrosion resistant synthetic resin coatings however have a poor adhesion which is time dependent and may loosen readily from the surface of the concrete structure.
We have discovered that the loosening of these corrosion resistant synthetic resin coatings may be due to moisture penetration. Concrete is, of course, impermeable to water in liquid form, but is permeable to water vapor. Diffusion processes, in which water in the vapor phase from the ground is transported through the wall of the concrete to the inside surfaces, appear to result directly in an accumulation of water at the interface between the corrosion resistant synthetic resin coating and the coated concrete surface.
The pressure behind the corrosion resistant synthetic resin coating so increases with time, that it eventually exceeds the strength of the coating on the concrete foundation, causing loosening, flaking, and peeling.