Research On Preparation And Properties Of Ni-Mo-P Conversion Coatings On Copper Alloy

The process conditions and property of nickel-molybdenum-phosphorous conversion coating were studied in this paper, and possible formation mechanism of the conversion coating is introduced. The orthogonal experiment method had been adopted to optimize the process conditions: nickel sulfate 30g/L,sodium hypophosphite 25g/L,ammonium molybdate 0.4g/L,sodium acetate 15g/L, pH value 9,time 90min.The influence on the coating formation of the master salt, complexing agent, stabilizer and buffers agents was studied, and the performance of the conversion coating on copper alloy was tested by acerbity corrosion test, physical experiment, and the results revealed that the influential factors of technology had significant influence on the film's corrosion resistance.The effects of the molybdate(Mo2O72-), temperature(T),pH value(pH) and reaction time to the conversion coating were studied by the electrochemical method(anode polarization measurement and EIS).A preliminary discussion has been done about the anticorrosion mechanism. The effect of parameters, such as pH value and Mo2O72- concentration, on the composition and structure of the Ni-Mo-P alloy deposits was investigated. The experimental results showed that there was a close relation between the Mo and P contents in the Ni-Mo-P alloy deposits, and the structure changed from amorphous to crystalline with the increase of the Mo content in the deposits.