Ni Coatings For Corrosion Protection Of Mg Alloys Prepared By An In-Situ Micro-Forging Assisted Cold Spray: Effect Of Powder Feedstock Characteristics

Three nickel (Ni) powders, i.e. gas-atomized spherical Ni (GA-Ni), carbonyl irregular Ni (C-Ni), and electrolytic dendritic porous Ni (E-Ni), were sprayed on magnesium alloys by an in-situ micro-forging assisted cold spray method. Although all deposited coatings present extremely low porosity, the C-Ni and E-Ni coatings reveal poorer inter-particle bonding than GA-Ni coating. Electrochemical tests reveal that the inter-particle gaps will act as fast pathways for the corrosive media to penetrate the coatings, thereby the GA-Ni coating with intimate interparticle boundaries can isolate the corrosive media for 3000 h and the C-Ni and E-Ni coatings fail after <10 h corrosion.