Cr–Ni alloy coating electrodeposited on T22 steel

Abstract

In present study, electroplating of Cr–Ni alloy was conducted on T22 steel substrate in a bath containing of trivalent chromium and divalent nickel ions. The effects of electroplating parameters (variation of current density from 10 A/dm2 to 30 A/dm2 and two–step electroplating process) and annealing temperature on morphology, microhardness, chemical composition and corrosion behavior of coating were investigated. Scanning Electron Microscope (SEM) and Energy Dispersive Spectroscopy (EDS) were utilized to observe the morphology and chemical composition of coating respectively. Potentiodynamic polarization test in 3.5% NaCl solution was utilized to evaluate corrosion behavior of the coatings. The experimental results showed that Cr and Ni were successfully deposited on T22 steel by using plating current density from 10 A/dm2 to 30 A/dm2. The two–step electroplating process was successfully applied for Cr–Ni electroplating. However, few cracks were observed on the Cr–Ni alloy deposit surface. The dense layer of Cr–Ni alloy deposits were obtained by annealing at 700°C for 60 min. In addition, better corrosion resistance of Cr–Ni alloy coating was achieved after annealed. It would be attributed to the formation of the dense layer of Cr–Ni alloy deposit.