Inspection of White Layer in Hard Turned Components Using Electrochemical Methods

This paper presents the results of electrochemical tests on hard turned steel components that have white layer on the surface. Electrochemical impedance spectroscopy is used to compare a machined surface with white layer against a machined surface without white layer, an annealed surface, and an electrical discharge machined surface. Measurements of the steady-state open-circuit potential are also used for comparison. The results show that the electrochemical properties of a surface with white layer are distinct from a surface without white layer. Specifically, a surface with white layer is more anodic and has lower electrochemical impedance than a surface without white layer in a NaOH solution. These results provide insight into the electrochemical properties of white layer and indicate that surfaces with white layer may corrode more quickly in service.