Effect of hydrostatic pressure on the corrosion behavior of HVOF-sprayed Fe-based amorphous coating

Understanding corrosion behavior under hydrostatic pressure is crucial for the design of materials for deep-sea industrial applications. In this work, the corrosion behavior of a Fe48Mo14Cr15Y2C15B6 amorphous coating was examined under high hydrostatic pressure (80 atm), and compared to that at atmospheric pressure (1 atm). The results from immersion and potentiodynamic polarization tests indicate that the general corrosion rate of the coating increased at 80 atm with respect to that at 1 atm, yet the localized corrosion resistance did not change much. However, the stability of passive films at 80-atm is declined compared to that at 1-atm, which is attributed to the lower compactness and higher density of point defects in the passive film at high hydrostatic pressure. Finally, TEM observations reveal that the passive film formed at 80 atm is much thicker (nearly 3 times) than that formed at 1 atm due to a faster dissolution rate of metals and diffusion rate of ions under high hydrostatic pressure, which have a compensation for the decrease of stability and compactness of the passive film, such that the good localized corrosion resistance of the amorphous coating is reserved at high hydrostatic pressure. This study sheds light on the dynamics of passive film formed on amorphous metals and will also be helpful for designing corrosion-resistant materials for deep-sea applications. (C) 2018 Elsevier B.V. All rights reserved.