Effect of Na2WO4 Concentration on the Microstructure and Corrosion Behavior of Ni-W-P Ternary Alloy Coatings

Abstract

Abstract Ni-W-P ternary coating was successfully deposited on AZ91D magnesium alloy by electroless plating with low energy consumption. The effect of Na2WO4 concentration on the microstructure, deposition rate, corrosion behavior, adhesion force, porosity test and micro-hardness of Ni-W-P ternary coatings were evaluated. Results reveal that when the concentration of Na2WO4 is 15 g/L in the plating solution, the coating with the average thickness of 17 μm is uniform and dense, and the content of phosphorus and tungsten reached 9.63 wt.% and 1.14 wt.% respectively, which presents amorphous structure. Meanwhile, when the concentration of Na2WO4 is 15 g/L, the amorphous Ni-W-P ternary coating has the best corrosion resistance, among which Ecorr is -0.326 V, Icorr is 0.003 A/cm2 in 3.5 wt.% NaCl solution. In addition, the mechanisms of corrosion resistance for the substrate and the coating were exploded.

Keywords

• Magnesium alloy
• Ni-W-P ternary coating
• Electroless
• Microstructure
• Corrosion behavior