Microstructure and Corrosion Properties of Plasma Arc Spraying Ni-based Coatings

Ni-based coatings were made on N80 steel by plasma arc spraying.The microstructure,chemical composition and the corrosion resistance of Ni-based alloy coatings were investigated by SEM/EDX,XRD,electrochemical and salt-fog test.The results showed that Ni-based alloy coatings constituted of Ni,Cr1.2Ni2.88,FeNi3,MoO2and CuO.In 5% NaCl solution,the corrosion current density of Ni-based alloy coatings was 1.2823×10-6 A/cm2,and only 1/50 of the N80 steel.In CO2saturated water and 3.5% NaCl solution,the corrosion current density of Ni-based alloy coatings was 1.074×10-6 A/cm2,and about 1/25 of the N80 steel.In the above two corrosion environment,the electrochemical polarization curves of Ni-based alloy coatings showed obvious passivation trend and the corrosion resistance of Ni-based alloy coatings was excellent.The salt-fog test displayed that the Ni-based alloy coatings exhibited better resistance than that of N80 steel,and the corrosion rate of Ni-based alloy coatings was about 1/3 of that of N80 steel.