MECHANISM OF THE SACRIFICIAL PROTECTION OF STRESSED LOW-ALLOY STEEL

摘要

We study the efficiency of sacrificial protection of stressed 40Kh low-alloy steel. Zinc and magnesium sacrificial anodes reliably protect steels against corrosion under elastic static and cyclic strains. In the plastic region, the efficiency of sacrificial protection decreases proportionally with stresses and is accompanied by oscillations of the current of the galvanic couple stressed steel specimen-sacrificial anode, which are attributable to juvenile areas on the strained surface of the steel and their repassivation. Correlations between the stresses that begin to cause corrosion losses of the steel at its sacrificial protection and current oscillations in the galvanic couple stressed steel specimen-sacrificial anode demonstrate a clear dependence of the efficiency of sacrificial protection on the intensity of current oscillations in the galvanic couple. We have established that loading of the steel stimulates the dissolution of the sacrificial anode, which can be explained by its electrochemical response in the galvanic couple to the deformational activation of the steel. Model experiments show that the rates of relaxation of strain-activated current of the galvanic couple and repassivation of the strained surface of the steel as well as the efficiency of sacrificial protection of the steel under loading are interrelated and depend on the speed of response of polarizing action of the sacrificial anode.