The effects of applied stress and sensitization on the passive film stability of AL-MG alloys

Abstract

This thesis evaluates effects of stress on the corrosion behavior for the aluminum magnesium alloy AA5083 in a comprehensive and systematic manner. This study used cyclic polarization and electrochemical impedance spectroscopy to study passive film stability of AA5083-H116, and sought to understand how applied and residual tensile and compressive stresses impact the passive layer film and the materials electrochemistry. Sample plates of AA5083 were sensitized to different levels to promote the formation of intergranular phase (Al3Mg2). The corrosion response of these sensitized plates was measured after laser peening and during the application of an elastic tensile stress. The corrosion response of these materials was sensitive to the application of a tensile stress. As sensitization increased, the material surface became more electrochemically active, but the stability of the passive oxide film also increased. The passive film stability was reduced by the applied tensile stress while the degree of passivity was slightly increased. No clear correlation between laser peening and surface corrosion chemistry was observed.