Effect of bath pH and stabilizer on electroless nickel plating of magnesium alloys

In order to develop the new bath solutions with long cycles and high stability for electroless nickel (EN) plating of magnesium alloys, effect of bath pH and pH stabilizers on plating rate and coating quality as well as bath life were studied in detail. Gravimetry was used to determine the deposition rate of coating. The coverage of coating was evaluated by 2 h of immersion test for magnesium alloys in 3.5 wt.% NaCl solution. The results showed that the bath pH not only changed the reactivity of the bath, but also had a strong impact on the microstructure and electrochemical properties of coatings. A highly uniform and dense coating was formed via EN plating in the new bath containing ammonium acetate. The bath life was extended when appropriate amount of ammonium acetate was added. It was effective for ammonium acetate to stabilize pH in the plating solution, to control coating quality and bath life.