Abstract
The characterization of passivation on austenitic and duplex stainless steels in soy sauce at 333 K were investigated by using electrochemical impedance spectroscopy (EIS). The soy sauce solution contained 18.4 mass% sodium chloride, 3.00 mass% organic acid, 6.80 mass% protein and 2.50 mass% ethyl alcohol at pH 4.9. These impedance spectra of stainless steels could been simulated the equivalent circuit model with four parameters, oxide capacitance, oxide resistance, charge-transfer reaction resistance and double layer capacitance. The thickness of passive films (reciprocal capacitance of films) were proportional to the resistance of films and charge transfer resistance.
