Anodic and Cathodic Behavior of Maraging Steel in Acid Solution

The polarization behavior of International Nickel Co. 18% nickel 250 maraging steel in acidic solutions has been studied by galvanostatic and potentiostatic methods. Results indicated that the corrosion potential was independent of chloride ion concentration, but dependent upon pH. Passivity was greatly affected by the chloride ion concentration of the solution. Very little difference in the polarization behavior was observed between the annealed and the maraging electrodes. Tafel behavior was not observed for the electrodes in sulfuric acid solutions. However, Tafel behavior of maraging steel was observed for 1N, 2N, and 10N HCl. Anodic Tafel slopes were 42 mv for both 1N and 2N HCl and 75 mv for 10N HCl; cathodic Tafel slopes were 160 mv for 1N and 2N HCl and 96 mv for 10N HCl. Chloride ions were shown to have a large effect on the passive current density of maraging steel between NaCl concentrations of 0.014% to 0.016%. Above an NaCl concentration of about 0.014%, electrochemical anodic passivity of maraging steel could not be maintained.