Galvanic Corrosion of AZ91D Magnesium Alloy

The galvanic corrosion behaviors of AZ91D magnesium alloy coupled with aluminum alloy,zinc alloy,Q235 carbon steel and copper were investigated in tap water and 3.5% NaCl solution.The effects of corrosion environment,coupled material and cathode to anode area ratio(CAAR) were discussed.During the corrosion process,pH of the electrolyte was measured and the galvanic currents of all couples were recorded.Meanwhile,the corrosion rate of AZ91D magnesium alloy was calculated by mass loss method,the corrosion morphologies of AZ91D were observed by SEM and the corrosion products were analyzed by XRD.The results showed that the pH of the electrolyte increased due to the galvanic corrosion of AZ91D magnesium alloy,the main corrosion product was Mg(OH)2,and the addition of NaCl would accelerated the galvanic corrosion rate of AZ91D magnesium alloy.Coupled materials with low hydrogen overpotential would promote the galvanic corrosion of AZ91D magnesium more seriously than that with middle hydrogen overpotential,the polarization property of coupled materials also had an obvious effect on galvanic corrosion of AZ91D magnesium alloy.Moreover,larger CAAR would result in faster galvanic corrosion,and the galvanic current of AZ91D magnesium alloy increased linearly with the increase of CAAR.