Advanced Nodular Thin Dense Chromium Coating: Superior Corrosion Resistance.

Abstract

Chromium-based functional coatings (CFCs) are widely recognized for their outstanding wear and corrosion resistance across diverse industrial sectors. However, despite advancements in deposition techniques and microstructural enhancements, many contemporary CFCs remain vulnerable to degradation in highly corrosive environments. For the first time, this research delivers a thorough characterization of the corrosion resistance of advanced CFCs, focusing on the performance of a 5 μm thin dense chromium (TDC) coating. These TDCs exhibit a distinctive, uniform nodular microstructure, characterized by approximately 3.6 μm nodules composed of defect-free near-nanocrystalline grains (227 ± 75 nm) plus enhanced electrochemical nobility. This structure promotes the rapid formation of a stable, dense bilayer oxide, resulting in a remarkably low corrosion susceptibility, effectively impeding both charge transfer and mass transport, particularly the diffusion of Cl^- ions. Furthermore, the coating sustains an exceptionally high polarization resistance over extended exposure times in aqueous NaCl electrolyte. These findings offer critical insights into the design of CFCs optimized for extreme environmental durability.