Enhancing the Electrochemical Behavior of AISI 304 Stainless Steel by Cyclic Potentiodynamic Passivation (CPP) Method

In this work, the effect of cyclic potentiodynamic passivation (CPP) on the electrochemical behavior of AISI 304 stainless steel in an alkaline medium simulating the concrete pore (0.1 M NaOH+0.1 M KOH) solution was investigated. CPP was very effective to enhance the open circuit potential of the sample. It was shown that the open circuit potential of the sample became 200 mV nobler by applying 100 cycles of voltammetry. Mott-Schottky analysis revealed that although CPP did not change the semiconducting character of the passive film, it reduced the charge carrier densities within the passive film. After applying 100 cycles of voltammetry, the donor density decreased from the initial value of 1.152x10(21) cm(-3) to 0.649x10(21) cm(-3), and the acceptor density decreased from the initial value of 0.953x10(21) cm(-3) to 0.574x10(21) cm(-3) Electrochemical impedance spectroscopy measurements showed that the passive film resistance of AISI 304 stainless steel was 75.6 k Omega.cm(2) before applying CPP method, while it was increased to 7735.7 k Omega.cm(2) after applying 100 cycles of voltammetry. All electrochemical tests showed that the electrochemical behavior of AISI 304 stainless steel was improved under the influence of CPP method, mainly due to the formation of thicker and also less defective passive film.