Effects of nitric acid passivation on the corrosion behavior of ZG06Cr13Ni4Mo stainless steel in simulated marine atmosphere

Abstract

AbstractZG06Cr13Ni4Mo martensitic stainless steel was nitric acid‐passivated to improve its corrosion performance. The effects of nitric acid passivation on the surface morphology, chemical composition, electrochemical properties, semiconductor behavior, and long‐term corrosion performance of the stainless steel were investigated using various analytical techniques. An in‐depth analysis of X‐ray photoelectron spectroscopy (XPS) showed that the passive film formed after the acid passivation process showed high thickness and a duplex character as it consisted of a hydroxide layer and an oxide layer. The oxide layer affected the corrosion resistance and thickness of the passive film. The thickness of the passive film was calculated theoretically as well as experimentally by fitting the electrochemical impedance spectroscopy and XPS results. The electrochemical tests revealed that the dramatic increase in the corrosion resistance of the stainless steel after the passivation was due to the formation of a thick, low‐disorder passive film rather than Cr enrichment. The removal of inclusions resulted in higher pitting resistance, whereas the increased roughness showed a negative effect on the corrosion behavior of the stainless steel. During the wet–dry cyclic tests, the modification of the passive film was examined. The passivated stainless steel exhibited good corrosion resistance for up to 50 days of exposure in the simulated environment.