Cold work effect on passivation and pitting corrosion resistance of Co-Cr-Ni-Mo-Nb alloy in chloride solution

The influence of strain on the structure and corrosion resistance of Co-20 Cr-19 Ni-3 Mo-Nb alloy have been investigated. The breadth of passivation area and the location of breakdown potential and repassivation potential have been defined on the basis of potentiodynamic curves. Moreover, the intensity of the solubility of selected alloy components against the degree of strain in cyclic anodic polarization conditions has been analyzed. A definite improvement with regard to pitting corrosion resistance has been found as result of cold working (a shift of breakdown potential Eb by 500 mV and the repassivation Er so be balanced with Eb alloy). On the presumed basis of a point defect model this improvement explained by existence of a great number of dislocations and the compressive stress in surface layer. The important part of the type of defects on the growth of passive layer durability and limitation of base digestion is indicated. (author). 31 refs, 6 figs, 1 tab