Corrosion resistance of intermediate temperature filler metal for stepped welding to 6063 aluminum alloy

The effects of contents of Si, Cu, Ni and RE on the corrosion potential, weightlessness and corrosion rate of Al-Si-Cu-Ni-RE filler metal were studied by using orthogonal test, and the microstructure of the corroded filler metal was analyzed by means of SEM and EDS.It is indicated that the corrosion potential of the filler metal is relative to its weightlessness, which with the increase of the negative value of corrosion potential, the weightlessness increases continuously.Based on the corrosion rates, the results show that Ni has the most important influence on the melting points, and then do Si, Cu and RE.Through observed and analyzed the microstructure of filler metal, it is found that the matrix phase α(Al) with face-centered cubic solid solution makes the performance of joint better, but black brittle phase θ(Al₂Cu) makes the performance of joint poorer;Cl^- is the prime cause of induced pitting corrosion of the filler metal, which the pitting corrosion in filler metal and the obvious inter-granular corrosion are found in local area after corrosion.