Effect of Food Grade Phosphoric Acid Concentration on Corrosion Resistance of Domestic 904L Stainless Steel

Potentiodynamic polarization curves and electrochemical impedance spectroscopy (EIS) were used to study the corrosion behavior of a domestic 904L stainless steel at room temperature in food grade phosphoric acid of different concentrations. And the corrosion morphologies were observed. The results showed that the domestic 904L stainless steel in 25% food grade phosphoric acid had good corrosion resistance. With the increase of phosphoric acid concentration, the natural corrosion current density Jcorr increased first, and then decreased. At the 40% concentration, the natural corrosion current density Jcorr was the largest and the corrosion resistance was the worst. Impedance spectrum curve consisted of the capacitive reactance arc at high frequency and the Warburg impedance at low frequency, inclicating that the corrosion of 904L was controlled by electrochemical reaction, and then turned to be controlled by material diffusion mainly.