PART 11. IRON-BASED METALLIC GLASSES WITH EXCEPTIONAL LOCALIZED CORROSION RESISTANCE IN CHLORIDE-BASED SOLUTIONS

摘要

The localized corrosion properties of a series of iron-based metallic glasses with a composition of either approximately (53-0.875x)Fe - (19-0.2x)Cr - 1.95Mn - (2.5+x)Mo - (1.65)W -(16-0.2x)B - (4-0.05x)C - (2.5-0.05x)Si (at%) or (48-0.5x)Fe - (15-0.133x)Cr - (14-0.133x)Mo - xW - (6-0.067x)B - (15-0.067x)C - (2-0.033x)Y (at%) have been studied in Cl~- containing solutions over a range of temperatures. Excellent resistance to pitting corrosion is observed in 0.6 M NaCl at 25亱C, 50亱C and 85亱C in the fully amorphous state. Pitting and crevice stabilization potentials were also predicted from experiments conducted on the same alloys in halide-containing solutions of low pH. These were created both artificially through the use of bulk HC1 solutions (0.1, 1, 5, and 10 Molar HC1 solution) and naturally using the artificial pit method. The predicted critical pitting and crevice potentials in the absence of initiation were related to the potentials, E*, E_T and E_(crevice) taken as the sum of the corrosion potential and overpotential required to achieve a critical pit stabilizing current density in a simulated acidified pit environment. Exceptional localized corrosion resistance in iron-based glasses in NaCl solution can be rationalized to be influenced by at least three factors. These include the large concentrations of Cr, Mo, and W, etc. in solid solution, minimization of surface defects as well as several different possible roles of minor and trace alloying elements such as boron, carbon, yttrium and silicon on transition metal oxidation under active dissolution in acidic solutions.