Microstructure and Corrosion Resistance of Plasma Sprayed Fe-Based Alloy Coating as an Alternative to Hard Chromium

Fe-based alloy coating (FAC) was prepared from Fe-based amorphous metallic powders on low-carbon steel by plasma spray. The microstructures and corrosion resistances (salt spray and electrochemical tests) of the FAC and the reference hard chromium coatings (HCC) were investigated. The results indicated that the as-sprayed FAC consisted of amorphous phase, nanocrystalline grains, and borides. Both the FAC and HCC adhered well to the low-carbon steel substrate, but there are micro-cracks and pores located in FAC, which disappeared after the sealing treatment. After 60 days (1440 h) of corrosion tests by salt spray, the weight loss of FAC was about 10% of the HCC, but that of the sealed FAC (SFAC) was only about 4% of HCC. The electrochemical tests indicated that the HCC had the lowest E (corr) (-629 mV) and highest I (corr) (63.2 mA/m(2)). Correspondingly, the SFAC possessed the highest E (corr) (-321 mV) and lowest I (corr) (6.97 mA/m(2)). These suggested that the resistance to corrosion sequence (R) among these coatings was R (SFAC) > R (FAC) > R (HCC). Therefore, this Fe-based alloy coating could be applied as a good alternative material to hard chromium in corrosion environments.