Corrosion behavior and passive stability of multilayer DLC-Si coatings

Abstract

In this research, multilayer DLC-Si films were effectively formed on the 2024 Al alloy utilizing cage-like hollow cathode discharge plasma-enhanced chemical vapour deposition (PECVD). A scanning electron microscopy (SEM), atomic force microscope (AFM), Raman spectroscopy, X-ray photoelectron spectroscopy (XPS), Fourier transform infrared spectroscopy (FTIR), and Nano Indenter G200 device were utilized to characterize the microstructural features of the coatings. Various electrochemical methods were used to investigate the anticorrosion performance of DLC films in 3.5 wt% electrolytic solution. The findings revealed that an increment in the bias voltage increases the condensation of the DLC layer and increments the thickness of the coatings. Furthermore, the outcomes revealed that the anodic current density and passive current decrements with an increment of bias voltage. This behavior is attributable to a good barrier impact of the amorphous DLC film. The multilayer film introduces new interfaces, resulting in the deterrence of Cl− ions penetrations. Further, the values of activation energy (∆E), enthalpy (∆H), and entropy of activations (∆S) for the samples in 3.5 wt% NaCl were determined and presented.