Water Lubrication of Polysiloxane-Containing Polyimide Coatings on Stainless Steel Substrates

This study investigated the water-lubricated tribological properties of coatings made of a novel polysiloxane-containing polyimide (si-PI) material that was recently developed for the aerospace industry and can be diluted with the harmless and environmentally friendly ethanol or water. The si-PI coatings were deposited on stainless steel (JIS SUS304) substrates at curing temperatures ranging from 160°C to 275°C. Their water lubrication properties were measured by rubbing the coatings against each other in water at room temperature. The coatings exhibited lower friction than conventional polyimide materials, with a minimum friction coefficient of 0.04, which was lower than that of polytetrafluoroethylene (PTFE) measured under the same sliding conditions. Unlike the conventional polyimide, the coatings did not exhibit any obvious wear or damage. The results demonstrate that the si-PI coating is a promising low-friction and highly durable coating for water lubrication.