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Magnesium dissolution was investigated using an on--line measurement of dissolved Mg and simultaneous time resolved volumetric analysis of hydrogen gas evolution. Testing was performed at open circuit potential and under anodic polarization in neutral, unbuffered chloride and buffered phosphate solution. IN the unbuffered chloride electrolyte, electrochemical dissolution occurs with a stoichiometry of n=2 and a significant enhancement of the corrosion rate at open circuit dissolution rate is observed following anodic polarization. The extent of the enhancement increases with anodic polarization time requiring at least 500 s to become detectable. In a phosphate buffer solution, neither the corrosion rate enhancement nor the negative difference effect (NDE) are observed. The kinetics of hydrogen evolution in non--buffered solutions tends to support a mechanism involving the activation of the cathodic reaction related to the disruption of a protective surface film. CORROSION Preprint http://dx.doi.org/10.5006/1459 NACE International corrosionjournal.org CORROSION Preprint http://dx.

International audienceCopper rich intermetallic particles are common in technical aluminum alloys. When exposed to an aggressive electrolyte, these particles undergo a transformation into a pure copper phase due to a selective dissolution or dealloying mechanism. In this work, the kinetics of this transformation have been investigated using synthetic intermetallic phases of Al2Cu, Al7Cu2Fe, and Al2CuMg in 2M H2SO4 as commonly used in the anodization process. The elementary dissolution rates for Al, Mg, Cu, and Fe were measured as a function of time and potential using atomic emission spectroelectrochemistry (AESEC). From this data, it was possible to measure the degree of selective dissolution for the individual elements in the different potential domains. Mg and Fe dissolve simultaneously with Al during the overall polarization. Al dissolution is activated in the presence of Mg and inhibited in the presence of Fe. This work demonstrates the utility of atomic emission spectroelectrochemistry for the direct measurement of dealloying reactions and the indirect measurement of residual films