Zn–Ni–W alloy based protective coating for enhancement of deteriorative properties in medium carbon steel substrate

Abstract

Medium carbon steel is one of the most abundantly used materials globally due to its availability, low cost, and wide range of properties. On the other hand, medium carbon steel has a significant disadvantage in terms of corrosion and wear resistance. In this research work the medium carbon steel substrate is electroplated with ternary alloy Zn–Ni–W to improve the hardness and resistance to corrosion in the steel substrate. Providing a Zn–Ni–W alloy sacrificial thin layers with a trace amount of W on the surface of a mild steel substrate improves its corrosion and wear resistance. The electrolyte composition is optimized in such a way that the coating is rich in Zn which makes it a sacrificial type coating. The coating is done in an acidic sulfate bath with current density and pH of 1 A/dm² and 5 respectively. The electrodeposition process is carried out at two different temperatures 55 °C and 70 °C with a deposition time of 30 min respectively. Surface morphology, chemical content, phase structure, and the thickness of these coatings are studied and compared using SEM, EDS, and XRD. Corrosion and wear behavior of Zn–Ni–W alloy coating has been done with the help of Electrochemical impedance spectroscopy (EIS). In conclusion, EIS results reveal notable characteristics for the Zn–Ni–W sample coated at 70 °C. The thin film exhibited a low corrosion rate and corrosion current, indicating a enhanced resistance against corrosion. Furthermore, the high polarization resistance value emphasizes the film's effectiveness in inhibiting corrosion processes. These findings collectively emphasize the favorable corrosion-resistant properties of the Zn–Ni–W coating deposited at 70 °C.