Stress and corrosion performance of amorphous Ni-Mo-P electroless deposits

This study investigated the stress, porosity and composition of amorphous NiMoP electroless deposits obtained from typical acid pH=4.6 and alkaline pH=8.0, their effects on corrosion performance of deposits in 5% NaCl and the generation mechanism of stress and porosity. The results indicate that the deposit obtained at a certain pH and Na2MoO4 concentration has the best corrosion resistance in 5% NaCl. With the increase of Na2MoO4 concentration, the stress was quickly changed from compressive to tensile stress, and the porosity was also increased. The higher were the stress and porosity, the poorer was remarkably the corrosion resistance. When the Na2MoO4 concentration was about 0.05g/L, the deposit with the highest corrosion resistance in neutral 5% NaCl was easily obtained. The corrosion resistance in the long time was mainly decided by the stress of deposits; the corrosion resistance in short time was mainly decided by the porosity of deposits. When deposits have no pore and low stress, the amorphous NiMoP alloys with higher Mo have better corrosion resistance; P in amorphous NiMoP films hasn′t obviously influences on corrosion resistance. The stress were measured by Xray analyzer and checked by the appearance immersed in 5% HCl for 35days. The corrosion performance was investigated by immersion corrosion tests, HNO3 corrosion blacking tests, porosity ferroxyl indicator tests and electrochemical corrosion technique. 