Electroless nickel-phosphorus deposition on carbon steel CK-75 and study of the effects of some parameters on properties of the deposits

摘要

Electroless nickel-phosphorus (Ni-P) deposition provides coatings with high hardness and excellent resistance to wear and abrasion. In this study, autocatalytic deposition of Ni-P alloy has been carried out on steel CK-75 sheets from bath containing nickel sulfate hexahydrate, sodium hypophosphite hydrate, thiourea, lactic acid, and sodium acetate. The effects of lactic acid concentration, pH and temperature on deposition rate, composition of deposits, and hardness have been studied. Also the changes in the hardness and structure of deposits by heat-treatment were studied by X-ray diffraction and scanning electron microscopy methods. It is shown that deposits crystallized after heat-treatment at 400℃ for 1 h and crystallization to Ni and Ni_3P was observed.