An ultrathin (ca. 5.0 nm thick), closely packed (self-assembly), tightly interconnected (two-dimensional polymer), and water-repellent (>130 degrees of the contact angle with water) film was prepared by modification of an 11-mercapto-1-undecanol self-assembled monolayer adsorbed on a copper surface with 1,2-bis(trichlorosilyl)ethane and subsequently with octadecyltrichlorosilane at 5 x 10(-4) M for 24 h. This film prevented copper corrosion in aerated 0.5 M Na2SO4 with the protective efficiency, P, of the film being maintained at over 95% in the solution for 15 h. The film provided excellent protection against indoor atmospheric corrosion of copper for 300 days. Effects of the surface roughness on the water repellence of the surface covered with the film and on the P value of an unmodified or modified alkanethiol monolayer were studied by using atomic force microscopy to examine mechanically abraded and electropolished copper surfaces.