In this study, the effect of worksheet surface characteristics on the electrical contact resistance of electrode-worksheet interface during resistance spot welding of aluminum alloy (AA5182) was discussed. The electrical contact resistance was influenced by both the oxide layer and surface roughness of the worksheet. However, the effect of oxide layer was more dominant, and the effect of surface roughness was likely to be linked with the damaging of oxide layer and not the contact area. The oxide layer on AA5182 was non-uniform with Mg-rich small spots dispersed on the surface. Grinding and scratching the worksheet surface was effective in reducing the oxide layer thickness and, hence, reduced the electrical contact resistance. It was observed that the surfaces with higher electrical contact resistances at this interface showed faster pitting rate of electrode. The study also suggested that the static electrical contact resistance measured before resistance spot welding could be useful for predicting materials likely behavior during the actual resistance spot welding process of AA5182.
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