Pitting corrosion of TiN film deposited on Inconel 600 by plasma assisted chemical vapor deposition (PACVD) was investigated. In this study the two types of pitting corrosion experiments were used: cyclic potentiodynamic polarization (CPP) and isothermal capsule tests.
CPP tests were performed in deaerated NaCl solutions at 25~200℃ at chloride concentrations ranging from 0.001 to 0.1 M. The pitting potential, $E_{np}$, decreases with the increases of chloride concentration and solution temperature. The morphologies of pits after polarization test were examined with a scanning electron microscopy and the pit products were analyzed with an energy dispersive X-ray spectroscopy. The pit aspect ratio and the composition of pit corrosion product are greatly affected by the solution temperature. For any test coditions, $E_{np}$ of TiN-coated Inconel 600 sample is much more noble than that of bare Inconel 600 sample. However, the open circuit potentials, $E_{corr}$, of both samples, Inconel 600 with and without TiN film, are almost same at 200℃.
Isothermal capsule tests were carried out in aerated $CuCl_2$ solutions at 200℃. TiN film deposited on Inconel 600 lowers the pit density and not affects the pit growth rate. The maximum pit depth of TiN-coated Inconel 600 is similar to that of bare Inconel 600. However, the pitting corrosion was found to be greatly retarded on TiN-coated Inconel 600 sample below a certain value of $CuCl_2$ concentration where there still existes pitting attack on bare Inconel 600.
