Effects of tungsten pre-implanted layer on corrosion and electrochemical characteristics of amorphous carbon films on stainless steel
By Liu, Chenglong; Xu, Ming; Zhang, Wei; Pu, Shihao & Chu, Paul K.
Published in Diamond and Related Materials
2008
Abstract
Amorphous carbon (a-C) films have been deposited on untreated and W pre-implanted (20 kV, 3 X 1017 ions/cm2) stainless steel substrates by plasma immersion ion implantation and deposition (PIII&D). X-ray photoelectron spectroscopy indicates that the transition layer consists of tungsten carbide (WC) and C. The corrosion behavior of the coatings is investigated electrochemically in 37 ± 1 °C simulated body fluids. In comparison with the a-C films, the a-C films with a W pre-implanted layer exhibit more positive open-circuit potentials, lower corrosion current density, and higher protection efficiency as indicated by potentiodynamic polarization tests. Electrochemical impedance spectroscopy reveals that the W pre-implantation layer increases the corrosion resistance of the a-C coatings in test solutions. The continuous structure caused by W pre-implantation layer is believed to not only offer good adhesion between the a-C film and steel substrate but also act as a barrier to mitigate penetration of water molecules and ions.