Corrosion Behaviour of a Laser-MIG hybrid welding-brazing Joint of 6061 Aluminium Alloy to SUS304 Stainless Steel

Lightweight steel-aluminium structures have broad application prospects because of their lowering weight characteristics, however, the corrosion of welding-brazing joints in steel-aluminium structures is less concerned or studied. In this paper, the corrosion behaviour of the Laser-MIG hybrid welding-brazing joints of steel-aluminium is investigated through the tests and analysis of salt spray, immersion and electrochemistry. The salt spray and immersion tests show that obvious galvanic corrosion occurs at the welded joints, in which the aluminium side is seriously corroded while the steel side is not corroded. The OCP values of the aluminium alloy and the weld metal are similar (approximately -0.48 V), and the stainless steel has a higher OCP value of -0.33 V. The corrosion resistance of the weld metal is lower than aluminium- as well as steel-base materials. The corrosion resistance of the joints is controlled by the aluminium alloy part of the two metals based on the open-circuit potential and EIS analysis. A possible corrosion process schematic for the physical/chemical properties of a welding-brazing joint immersed in a sodium chloride solution is proposed according to electrochemical impedance spectroscopy.