The Corrosion and Wear-Corrosion of the Iron-Base Amorphous Coating Prepared by the HVOF Spraying

Abstract

In this work, the corrosion behaviors of an iron-based amorphous coating produced by high-velocity oxy-fuel (HVOF) spraying were investigated. Potentiodynamic and potentiostatic polarization and corrosion pin-on-ring (corrosion-wear) tests were conducted to evaluate the corrosive properties of the coating as compared with the 316L substrate. The corrosion behaviors of the 316L substrate and coated sample were tested in 3.5 wt.% NaCl, 1 M HCl, and 0.5 M H2SO4 solutions. In the 3.5 wt.% NaCl and 1 M HCl solutions, the corrosion resistance of the coating was a little inferior or equivalent to that of the 316L substrate after potentiodynamic polarization tests. In the 0.5 M H2SO4 solution, the two tested samples exhibited wide passivated zones in the polarization curves. In such a mild acid, the corrosion resistance of the 316 substrate was superior to that of the amorphous coating, possibly due to the presence of defects in the coating. After potentiodynamic polarization tests, the linkage of initial fine pits into large, deep pores was seen in the corroded 316L substrate. By contrast, extensive corrosion along with preferentially corroded defective sites was seen in the coating. Moreover, the coating exhibited a much higher resistance to corrosion-wear, or low weight loss, in 3.5 wt.% NaCl solution. After the corrosion-wear tests, deep furrows were present in the 316L substrate, whereas a rubbed smooth surface and a corroded zone were seen in the coating. The greater weight loss of the 316L substrate confirmed its poor resistance to corrosion-wear relative to the amorphous coating in 3.5 wt.% NaCl solution.