Abstract: Static weight loss method was utilized to measure the average corrosion rate of friction stir weld 2A12 aluminum alloy joint under 3.5% NaCl solution. The variation of corrosion rates under different corrosion time was studied based on the analysis of corrosion mechanism, corrosion product composition and morphology of corrosion damages. Results showed that the average corrosion rate decreased dramatically at the beginning and then rose slowly which was closely related to the change of corrosion mechanism from pitting to intergranular corrosion, which finally became to exfoliation corrosion. The weld was corroded more seriously under longer corrosion time according to the quality removal ratio. Different zones of the weld have different corrosion sensibility, namely, the weld nugget has most serious corrosion, followed by the front side and the retreating side was corroded slightly.