The majority of automotive body shop welding consists of resistance spot welding (RSW) steel sheet due to its inherently low cost and high speed. With the introduction of aluminum, it is desirable to continue using RSW as the joining process. However, the presence of insulating oxide layers on the aluminum alloy material surface presents significant problems in obtaining consistent spot welding processes. If dressing fails to completely remove the pits, it will cause the electrode surface to deteriorate more rapidly, which in turn will eventually lead to unacceptable welds. Macrodeformation of the electrode, which commonly happens in steel spot welding, does not occur for aluminum spot welding because the nugget temperatures are much lower. However, circular protrusions on the MRD electrode with their small cross sections can be susceptible to deformation or flattening during use.