Many magnesium alloys exhibit microgalvanic corrosion due to anodic and cathodic reactions that occur at discrete phases. We used the scanning vibrating electrode technique (SVET) to map the local corrosion current distribution profile of specially designed magnesium and aluminum galvanic couples. We studied the effect of anode (Mg) to cathode (Al) area ratio (A/C = 1:9, 3:7 and 1:1) and the effect of electrolyte concentration (sodium chloride solutions, 10, 30, and 280 mM). The galvanic current density is mapped for different immersion time intervals (t= 0 and 1 hour). The SVET response clearly showed that anodic and cathodic current densities on the magnesium and aluminum (Mg-Al) galvanic couple, respectively. The current density decreased with increasing anode to cathode surface area ratio, and at a given ratio, increased with increasing concentration of the sodium chloride solution. Our results showed that SVET can provide finite current/potential details of the microgalvanic activities within magnesium alloys, which are not possible with conventional electrochemical measurements, and it is an excellent measurement tool for understanding microgalvanic corrosion of magnesium alloys.

Subject
Galvanic anodes, Magnesium anodes, Galvanic cathodes, Anode surfaces, Density, Sodium chloride solution, Current densities, Salt concentration, Cathodic current density, Magnesium, Immersion, Galvanic current, Electrodes
Keywords:
Microgalvanic corrosion, magnesium galvanic corrosion, SVET
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2009
Association for Materials Protection and Performance (AMPP)
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