Residual stresses and corrosion performance of plasma sprayed zinc-based alloy coating on mild steel substrate

Plasma spraying technique stands out among the various processes for enhancing the surface characteristics of engineering materials. Many authors have conducted research on different types of deposition technologies in relation to the corrosion performance of different coatings. However, not all aspects of these processes are fully understood. This study focused on the residual stresses and corrosion behaviour of plasma sprayed zinc-based alloy coatings on mild steel substrate. Characterization of coated surfaces was done using optical microscopy, X-ray diffraction, and scanning electron microscopy to observe the morphology, phases, grain sizes and probable defects. The residual stresses were measured by X-ray diffraction sin²Ψ techniques using Cu-Kα radiation. The corrosion and micro hardness properties were investigated using Auto lab potentiostat (PGSTAT30) linear potentiodynamic polarization and Emco Dura Scan tester. The experimental results revealed an improvement in the corrosion and micro hardness properties of the coated samples as compared to the substrate. The residual stresses of the as-sprayed coatings show compressive stresses. The magnitudes of the stresses in the as-sprayed condition were low, with slight variation due to the effect of cooling and difference in powder compositions. Overall, zinc-base coatings have significant positive effects on the corrosion performance, mechanical properties and residual stresses of the substrate.