Microstructure, mechanical, and electrochemical properties of Si/DLC coating deposited on 2024-T3 Al alloy

This work evaluated the microstructure, mechanical, and electrochemical properties of Si/DLC coatings deposited using ‎ the plasma-enhanced chemical vapor deposition (PECVD) technique. Tetramethylsilane and acetylene were used as precursor gases in the deposition process. The characteristics of the coating were estimated using different techniques. The corrosion performance was evaluated using various electrochemical methods in 3.5 wt. % NaCl solution. The XPS analysis revealed that the film consists of Si and (a-C: H). The results revealed that as the deposition time increased, the hardness and Young's modulus decreased from 15.83 to 14.21 GPa and 125.8 to 114.9 GPa, respectively, while the thickness and adhesion strength increased. Moreover, the anti-corrosion ability of the DLC has been improved. It was found the corrosion potential moved to more noble direction (-618 to -562 mVAg/AgCl) while the corrosion rate decreased from 0.012 to 0.001 mmy-1. This trend can be attributed to growing coating thickness and fewer film defects which operated as a protective barrier against the corrosive solution. A failure mechanism of Si/DLC film has been suggested.