Investigation of corrosion behavior of Mg-steel laser-TIG hybrid lap joints

The paper investigates the corrosion behavior of the lap joint of AZ31 magnesium alloy to Q235 steel with salt solution immersion testing and electrochemical testing. It is demonstrated that grain refinement resulting from the welding process has little effect on the corrosion behavior of the lap joint. However, the cathodic phases formed in the welding process and the galvanic corrosion between magnesium alloy and steel decrease the corrosion resistance of the joint greatly. Besides, neither Cu nor Ni, as filler material, could improve the corrosion resistance of the joint, but the arc-sprayed Al coating acting as a protective layer could.

► Galvanic corrosion increases the corrosion rate of the Mg-steel joint.
► Fe splashes lower the corrosion resistance of the joint greatly.
► The effect of grain refinement on the corrosion behavior of the joint is slight.
► Ni or Cu interlayer could not improve the corrosion resistance of fusion zone.
► The arc-sprayed coating could enhance the reliability of weld joint.