Process of environmentally-friendly direct electroless nickel plating on AZ91D magnesium alloy surface

Abstract

In order to improve the corrosion resistance and wear resistance of magnesium alloy efficiently and environmentally, the corrosion resistant and wear resistant coating were prepared on AZ91D magnesium alloy by direct electroless nickel plating without fluorine, chromium, cyanogen and zinc. The surface morphology, composition, phase and corrosion resistance properties were characterized and compared by SEM,EDS,XRD and electrochemical workstation respectively. The results show that the coatings are smooth and compact, consisting of fine and uniform cellular structure being mainly composed of 85.25%(mass fraction) amorphous Ni and P in the ratio of main salt to reductant is 1:1.4,complexing agent concentration is 16 g·L-1, pH=7 and the temperature is (85±0.5) ℃.The hardness is increased from 72HV of substrate to 285HV. Corrosion potential is enhanced from -1.524 V(substrate) to -0.513 V, meanwhile the corrosion current density is decreased by about 3 orders of magnitude. The cohesion between the substrate and the deposition layer is good without peeling and falling off, and the thickness of the deposition layer is approximately 38 μm.

Keywords

• magnesium alloy
• direct electroless plating
• az91d
• environmentally friendly
• corrosion resistance