Galvanic corrosion of magnesium alloy and aluminum alloy by kelvin probe

Galvanic corrosion on samples of AZ91D magnesium alloy coupled with 2A12 aluminum alloy during neutral salt spray test was investigated. The variations of the surface potential were measured using scanning kelvin probe (SKP). The results showed that galvanic effect on the corrosion of AZ91D magnesium alloy is closely related to the potential difference between the anodic and cathodic materials. In the initial period, corrosion only occurred in a narrow area at the coupling interface because of the limited distance galvanic current. Then, the corrosion rate of 2A12 aluminum alloy was accelerated due to its poor stability in strong alkali environment, which was attributed to the strong alkalization caused by the corrosion of AZ91D magnesium alloy. With the increase of the potential of 2A12 aluminum alloy as a result of the continuous covering of corrosion products, the potential difference between the two materials was enlarged, which enhanced the galvanic corrosion.