A combined microstructural, electrochemical and nanomechanical study of the corrosion and passivation properties of a Cr/CrN multilayer coating

This research provides detailed insights into the correlation of microstructural and morphological characteristics of a Cr/CrN multilayer coating deposited onto steel and its corrosion behavior, by examining its local surface electronic properties, nanomechanical behavior, and electrochemical activity in a 3.5 % NaCl solution. A key focus of the study is the influence of physicochemical surface evolution on nano-mechanical properties of Cr/CrN coating. This is investigated by correlating electrochemical data from electrochemical impedance spectroscopy (EIS) with findings from X-ray photoelectron spectroscopy (XPS) and nanoindentation analysis. The integrated approach shed light on physicochemical evolution of the coating, and its resistance to corrosion in demanding environments. • Difference in surface potential between CrN and Cr layers promotes micro-galvanic coupling and accelerating corrosion. • Increasing anodic overpotential shows CrN layer breakdowns, followed by minor passivation from thin Cr layers. • Passive film enhances total resistivity initially but degrades after 5 h exposure due to Cl − -induced corrosion. • Corrosion-induced softening weakens CrN top-layer, reducing hardness and elastic modulus after exposure 24 h in NaCl.