Different corrosion behaviors of Sn-based modification coatings on magnesium alloy surface via plasma-involved processes: FCVA deposition vs MEVVA ion implantation

In this work, the surface of WE43 was modified with Sn ions using a composite device with both filtered cathode vacuum arc (FCVA) and metal vapor vacuum arc (MEVVA) functions. The influences of Sn ions on the surface morphology, elasticity modulus (EIT), nano-hardness (HIT), and corrosion resistance of WE43 after modification by different treatments were comparatively studied. The corrosion mechanism was also elaborated from the perspectives of corrosion kinetics and oxidation process. The results proved that the modulus of elasticity of the samples increased after the Sn ion modification of WE43 by both FCVA and MEVVA, in which the EIT increased from 55.24 to 57.04 GPa after FCVA modification. The FCVA technique covered the surface of the samples with a uniform Sn film, however, the difference in potential between Sn and Mg was too large which aggravated the galvanic coupling corrosion. After the injection of Sn ions, a modified layer consisting of SnO₂ and Sn was successfully formed on the sample face. The electrochemically measured I_corr of WE43, Sn-implanted and Sn-deposited were 23.15, 17.88 and 65.25 μA⋅cm⁻². The results of the immersion experiments demonstrated that SnO₂ effectively impeded the dissolution of Mg (OH)₂, resulting in the formation of a uniform and dense corrosion product film that enhanced the corrosion resistance of WE43.