Study on Galvanic Corrosion Behavior of Steel/Aluminum Laser-MIG Hybrid Welding-Brazing Joints

The galvanic corrosion behavior of a laser-MIG hybrid welding-brazing joint of 6061 aluminium alloy to SUS304 stainless steel was studied by combining experiment and simulation.The corrosion behavior of the joint was researched by conventional electrochemical method and micro area electrochemical methods (scanning Kelvin probe system, SKP and localized electrochemical impedance spectroscopy, LEIS).The large-scale simulation software COMSOL Multiphysics was used, and a corrosion simulation model for the galvanic couple of stainless steel/Al-alloy welded joint was established, the exchange current density of the base metals in neutral 3.5% NaCl solution was estimated by electrochemical polarisation, which was used as the boundary conditions in the simulation.The results show that the corrosion resistance of steel/aluminum dissimilar metal welding-brazed joint is lower than that of base metals, and its corrosion resistance decreases with the decrease of solution pH value.The simulation results are consistent with the experimental results, the weld potential is between that of the two base metals.The potential of the metal at the aluminum side is lower, which is used as the anode for corrosion, and the corrosion occurs preferentially at the interface between intermetallic compound(IMC)and aluminum weld.