Corrosion Resistance of 9Cr1Mo Steel with Citric Acid Passivation in Marine Atmosphere Environment

In order to improve the corrosion resistance of 9Cr1Mo steel in marine atmospheric environment, the citric acid passivation and citric acid-hydroxide composite passivation were selected to passivate the 9Cr1Mo steel. Their effects on the corrosion performance of 9Cr1Mo steel were investigated, and the reasons for the enhanced corrosion resistance of 9Cr1Mo steel treated by citric acid passivation treatments were analyzed. The results showed that the 9Cr1Mo steel without passivation treatment underwent serious corrosion in both simulated and real marine atmospheric environments. The protective passive film was able to be formed on the surface of 9Cr1Mo steel by two kinds of passivation treatments, which ensured that the passivated 9Cr1Mo steel did not be corroded within 78 days in the real marine atmosphere. The corrosion resistance of 9Cr1Mo steel in marine atmospheric was remarkably enhanced by passivation treatments. Citric acid and citric acid-hydroxide composite passivation process could increase the content of Cr₂O₃, Cr(OH)₃ and oxides in passivation film, and those content was significantly higher than that of hydroxide, thereby improving the stability and corrosion resistance of the passive film.