Study on the corrosion performance of supersonic atmospheric plasma sprayed Cr₃C₂-NiCr coatings

Purpose Due to the harsh underground environment in coal mining, the surface of hydraulic support columns corrodes severely, resulting in significant economic losses. Therefore, a highly corrosion-resistant coatings is needed to extend the service life of the columns. Design/methodology/approach This study aims to compare the corrosion resistance of ST-Cr 3 C 2 -NiCr (sealed treatment Cr 3 C 2 -NiCr) coatings with industrially applied chromium plating. The corrosion failure mechanism of the coatings was investigated. Findings The results demonstrated that the ST-Cr 3 C 2 -NiCr coatings exhibited excellent corrosion resistance. After sealing treatment, the corrosion potential of Cr 3 C 2 -NiCr coatings was −0.215 V, and the corrosion current density of Cr 3 C 2 -NiCr coatings was lower than that of the plated parts. Practical implications ST-Cr 3 C 2 -NiCr coatings prepared by supersonic atmospheric plasma spraying could provide excellent corrosion resistance in the coal industry. Originality/value The low porosity and the presence of the NiCr phase were crucial factors contributing to the preferable corrosion resistance exhibited by the ST-Cr 3 C 2 -NiCr coatings. The corrosive process of the coatings involved layer-by-layer delamination of surface oxide film, sub-surface pitting, formation and degradation of sub-surface passive film, as well as severe block-like delamination.