Evaluating the performance of sputter-deposited Aluminium alloy-based coatings on steel in the light of grain orientation, surface roughness, and corrosion behaviour

• Published in: Canadian metallurgical quarterly 2022-07, Vol.61 (3), p.251-264
• Main Authors: Murmu, Uttam Kumar, Roy, Avinava, Ghosh, Arkajit, Eivani, Ali Reza, Dutta, Monojit, Ghosh, Manojit
• Format: Article
• Language: English
• Subjects: Aluminium alloy coatings; coating thickness; corrosion; electrochemical impedance spectroscopy; Magnetron sputtering; salt spray test; surface roughness; texture coefficient
• ISSN: 0008-4433; 1879-1395
• DOI: 10.1080/00084433.2022.2035635

Magnetron sputtering has been one of the significant processes for developing defect-free uniform coatings for a wide range of materials. Increasing Magnesium (Mg) content in Aluminium (Al)-Mg sputtered coats has been strongly linked to a heightened sacrificial nature. This has directed researchers towards investigating different combinations or compositions of Al-based coats. Sputtered Al coats having minute proportions of Zinc (Zn) and Mg could be promising in terms of offering a corrosion-resistant coating on steel substrates. This has prompted a detailed analysis of three different coatings deposited on 4130 grade IF steel substrates using pure Al, Al-Mg and Al-Zn-Mg as targets by magnetron sputtering. For a fixed deposition time of 10 h, thickness of the coatings were in the order: Al-Zn-Mg > Al > Al-Mg. The coatings were investigated in terms of the microstructure, corrosion behaviour, surface roughness and coating adhesiveness. XRD was conducted to study the evolution of phases with increasing coating thickness. Al-Zn-Mg coating was found to be the most durable one, in terms of corrosion resistance, through EIS and SST and role of surface roughness was identified as a critical controlling factor, which was outweighed by the coating compositions. Although this ternary coating exhibited unsatisfactory performance during bend test, it has been hypothesized that tailoring texture coefficients could be a promising way to attain an optimum combination of oxidation resistance and adhesion.