ELECTROCHEMICAL IMPEDANCE SPECTROSCOPY OF PVD-TIN COATINGS ON MILD-STEEL AND AISI316 SUBSTRATES

The electrochemical and corrosion behavior of PVD-TIN coatings was inv estigated through electrochemical impedance spectroscopy (EIS) in a 3% NaCl solution. Mild steel (active) and AIS1316 stainless steel (passi ve) substrates were employed. The results indicated that it was possib le to follow the corrosion of the active substrate using EIS over a pe riod of 500 h immersion. The AIS1316 substrate, however, remained effe ctively passive for the duration of the experiment. Based on this stud y, the EIS technique certainly shows promise in assessing the corrosio n performance (and the coating quality) of electron-beam plasma-assist ed PVD-TiN coatings on active substrates such as mild steel. Its usefu lness on passive materials appears more limited, owing to the similari ty of the electrochemical impedance response of the coating and substr ate.