Papers by Keyword: Repassivation

Abstract: Hydrogen entering into steel affects its electrochemical properties and may enhance the susceptibility to environmental degradation. The present work has been aimed at further clarifying the effect of hydrogenation on the corrosion behaviour and passivity of highly-alloyed stainless steels. The results were discussed by taking into account hydrogen charged samples and without hydrogen. The corrosion resistance to pitting was qualified with the cyclic polarization curves. The conclusion is that hydrogen may deteriorated the passive film stability and corrosion resistance to pitting of highly-alloyed stainless steel. Furthermore, the presence of hydrogen in passive films increases corrosion current density, decreasing the potential of the film breakdown and repassivation potential. It was also found that the degree of susceptibility to hydrogen-enhanced pitting corrosion was dependent on the type of steel.

Abstract: Electrochemical chloride extraction (ECE) is used for the rehabilitation of chloride-contaminated concrete. High current densities of steel surface are applied between the steel and a temporary external anode which is placed on the concrete surface. Anions are pushed away from the cathode (steel reinforcement), and cations are accumulated at the cathode. In this study chloride ions were found in the electrolyte during ECE. The extraction efficiency of chlorides was obvious. After treatment, the amount of chlorides around the reinforcement was greatly reduced. ECE had insignificant effect on the compressive strength. Steel potentials in treated specimens showed a strong shift towards more positive values, while potentials in control specimens remained strongly negative.

Abstract: In order to investigate the intergranular and pitting corrosion behavior of Fe-25Al-6Cr intermetallic compounds containing Mo, Nb and B, 11 kinds of Fe-25Al were prepared by arc melting in Ar gas, using high purity aluminum and iron. The fabricated materials were heat treated for homogenious structure and stabilization of the iron aluminides. The electrochemical methods were used for interganular and pitting corrosion. Effects of Mo, Cr, Nb and B on the repassivation current density(Ir) and the active current density(Ia) of Fe-25Al-6Cr were recorded in the following order: MoCr>Nb>B, from the highest to the lowest respectively.