Electroless generation of phosphate films on metals from zinc dialkyldithiophosphates

An electroless (solution growth) technique based on the thermooxidative dec omposition of zinc dialkyldithiophosphates (ZDDPs) in solution, has been de veloped for the deposition of thin phosphate films on a wide variety of met als including gold and silver. An additional annealing step in air results in a uniform? sturdy, and well-adhering film, consisting of small (submicro meter) intergrown particles bonded to the metal surface. The coating proces s is very simple and well controlled. Any shape can be coated. Films rangin g in thickness from 10s to 1000s of angstroms can be generated reproducibly , depending on the solution temperature and time of heating. These films ar e very hard, have excellent mechanical stability and reasonable chemical st ability, and should be useful for many protective purposes.