Improvement in Tensile Strength of Mg Alloy After Immersion in SBF by Cold-Sprayed Zn Coating

Considering corrosion on mechanical property of Mg alloy in simulated body fluid, cold-sprayed Zn coating was prepared onto Mg alloy substrate in order to improve its tensile strength after immersion in stimulated body fluid. Tensile strength and corrosion behaviors of bare and Zn-coated Mg alloy were investigated after different immersion time. Results show that comparing with deep and large corrosion pits on bare samples after immersion, Zn-coated Mg alloys exhibited shallow and small corrosion scars on Zn coating, and the Zn coating effectively delayed the corrosion attacks on Mg alloy substrates. The pH increment and Mg ion release in immersion medium for Zn-coated samples were lower than that of bare samples due to the corrosion protection of cold-sprayed Zn coating. Zn-coated Mg alloys after immersion of 28 days exhibited an ultimate tensile strength of 247.2 ± 9.2 MPa and yield strength of 181.7 ± 6.8 MPa, which was higher than that of bare Mg alloys by 11.9% and 16.7%. The main fracture mechanism of the bare and Zn-coated Mg alloys during tensile testing transformed from ductile fracture to brittle fracture after immersion, which can be attributed to stress concentration caused by localized corrosion pits. Improvement in tensile strength of Zn-coated Mg alloy after immersion was discussed from the viewpoint of corrosion attacks.