Surfacial Modification of Magnesium-Lithium Alloy

Abstract

A novel process of electroless Ni-P plating on magnesium-lithium alloy is discussed in this paper, by which nickel ions are provided by basic nickel carbonate and a new pretreatment method is introduced to obtain good quality coating. The corrosion behavior of magnesium-lithium alloy without or with coating was compared and the bonding strength of the electroless Ni-P coating to the matrix surface was also measured. The results showed that the process of electroless Ni-P plating can be easily achieved on the intermediate layer and a compact Ni-P coating without flaws is formed synchronously. The thickness of Ni-P coating is above 20 μm and its phosphorus content is about 10.501wt.%. The corrosion potential of magnesium-lithium alloy coated by Ni-P increases obviously (-0.315V) during the anodic polarization in 3.5 wt. % NaCl solution and this phenomenon indicates that an effective protection has been formed for the alloy. It was proved that the Ni-P coating adheres on magnesium-lithium alloy surface tightly through the file test and cross cut test.