Tribological Behaviors of Lubricants Modified Nanoporous Anodic Alumina Film

A uniform closely packed hexagonal array of porous anodic alumina (PAA) film with an average pore diameter of ~100 nm and a pore height of ~330 nm was obtained by anodizing in oxalic acid solution. Low surface energy molecules of perfluoropolyether (PFPE) and octadecyltrichlorosilane (OTS) were used to enhance the hydrophobicity of the PAA and aluminum (Al) surface. The tribological performances were investigated in detail. The results showed that the static friction coefficient of PAA was much lower than that of smooth Al, which could be due to the higher hardness of the PAA than that of Al. PAA modified with PFPE was characterized by lower friction coefficient and longer wear life as compared with bare Al, PAA, and PAA modified with OTS. This is caused by the combined effects of flexibility, mobility, and inherent lubricity of PFPE molecules and the nanoporous structure of PAA as a reservoir for lubricants and wear particles.