Enhancement in the corrosive and tribological properties of the inner wall of 6063Al and CI pipes by thick multilayer Si-DLC coatings

Abstract

Corrosion and wear on the inner wall of metal pipes is considered as a challenging issue for their service lifetime in application of delivery systems. Diamond-like Carbon (DLC) coating is a widely investigated material and one of the best choices to be used as protective coating. In this report, Thick multilayer Si-doped DLC (Si-DLC) coatings with high quality was deposited on the inner wall of 6063 aluminum alloy (6063Al/Si-DLC) and cast iron (CI/Si-DLC) pipes by hollow cathode plasma enhanced chemical vapor deposition (HC-PECVD). The structure of the as-deposited coatings on 6063Al and CI pipe are similar, which consists of 10 deposition periods. Electrochemical impedance spectroscopy (EIS) and potentiodynamic polarization tests were employed to assess the corrosive resistance of 6063Al/Si-DLC and CI/Si-DLC in 3.5 wt% NaCl solution. The long-term corrosive resistance of the coatings system was measured by neutral salt spray test. Compared with bare 6063Al and CI pipes, 6063Al/Si-DLC and CI/Si-DLC possess excellent corrosion resistance and long-term stability when exposed to corrosive medium, which attributes to the deposition of the coatings on bare substrates. In addition, 6063Al/Si-DLC and CI/Si-DLC show lower and stable friction coefficients and lower wear rate. Consequently, the coatings system what afforded in this study is an extremely potential design to enhance the service life of 6063Al and CI pipes for industrial delivery.