Developing a Step by Step Understanding of Physical and Microstructural Features of HVOF Coatings by Impedance Spectroscopy Modelling

The corrosion of HVOF metallic coatings is a complex electrochemical process where numerous physical and electrochemical processes occurred at the surface. Researchers have adopted different approaches to study these processes. A significant cache of research material is available online, where researchers have reported electrochemical corrosion testing techniques complemented with passive layer characterization and microstructure analysis. Some others published their work supported by complicated mathematical modelling concepts and equations. This study focuses on developing a step-by-step understanding of the physical and microstructural features of HVOF coatings by electrochemical impedance spectroscopy. First, the different physical characteristics of the coating are envisaged, and their corresponding equivalent circuit models are constructed. Second, using simulation software, the impedance of each circuit is simulated by giving seed values to each circuit component. Third, after building up the necessary background, a model is constructed for the HVOF Inconel 625 coatings to see the quality of fit with the experimental data. Although the quality of fit is not perfect, still, the step-by-step modeling and simulation of the corrosion processes at the coatings add value to the knowledge in electrochemical corrosion testing.