Organosilanes of the general formula R-Si (ORI)₃ have been examined as adhesion promoters for two pack urethane and epoxide paints on aluminum and mild steel substrates when incorporated into the paints prior to application. The silanes are effective at concentrations between 0.1 and 0.6 percent by weight and produce major improvements in the initial, wet and recovered bond strengths. Improvements in the bond strengths after exposure to hostile environ ments were observed. Long-term storage tests have shown the improvements to be maintained over a period of two years.