Investigation of nickel-chromium coating effect on corrosion of mild steel pipe by electroplating method

Abstract

Nickel-chromium (Ni-Cr) coating as an alloy is applied on the carbon steel surface by electroplating technology with a thickness of (60-63) μm to investigate the role of this coating through many characterization tests, antibacterial tests, and electrochemical tests. The identification by X-ray diffraction gave peaks at 2θ 45.28° and 52.28°, related to deposit α‒ (Cr, Ni), confirming the deposition of Ni-Cr alloy as a coating. Scanning electron microscopy gave a dense compact layer over the coated sample, and atomic force microscopy showed more ordering in particles with higher roughness (increasing from 2.26 to 2.73 nm). The observation of antibacterial examination indicated the complete inhibition zone for the coating layer. The electrochemical observations gave the more noble potentials and less current densities for the coated sample compared with the uncoated one at a constant temperature, with good protection efficiencies ranging from 99.82 to 99.95%. The change in free energy is less spontaneous for corrosion in the coated sample (where it changed from -149.093 to -17.8332 kJ.mol -1   for uncoated and coated, respectively, at 30°C), in addition to getting less entropy (shifting from 0.46011 to 0.34228 kJ.mol  after coating) and obtaining less exothermic behavior after coating, changing from -212.30 to -165.84 kJ.mol -1 -1 .K  at 30°C.