The electrochemical corrosion behavior of TiN and (Ti,Al)N coatings in acid and salt solution

In this study, the corrosion properties of TiN and (Ti,Al)N coatings fabricated by Hollow Cathode Ionic Plating (HCIP) were studied by electrochemical techniques such as electrochemical impedance spectroscopy (EIS) measurement and potentiodynamic measurement in acid and salt solution. It was found that both coatings showed an excellent corrosion resistance in acid and salt solutions at the beginning of long-term immersing test. The corrosion resistance of TiN coating deteriorated rapidly after nearly 100 h immersion in both acid and salt solutions. In the contrast, the corrosion rate of (Ti,Al)N coating decreased a little and then kept at a stable value. For the TiN coating, the corrosion initiated from pinholes and the underlying corrosion was very similar to pitting corrosion. With the addition of aluminum to the TiN coating, the corrosion resistance was improved, especially in salt solution. The test results demonstrated that the (Ti,Al)N coating seemed to posses certain self-repairing function. The corrosion mechanism took the form of denudation corrosion, owing to deterioration of the adhesion of the coating.