Corrosion resistance of the chemically treated austenitic stainless steel in relation to temperature

Com. Ti-stabilized Cr-Ni-Mo austenitic stainless steel was passivated with HNO3 soln. and then studied for pitting corrosion in 5% FeCl3 soln. (pH 1.2) by 24-hours std. immersion test and in 0.9 M NaCl + 0.1 M HCl soln. (pH 1.1) by electrochem. impedance spectroscopy (EIS test) at 22-80 degrees C. The pits were significantly bigger at 22 degrees C than those at 50 degrees C but the distribution of pitting was markedly lower. The polarization resistance decreased with increasing the temp. The quality of the surface passive film was several times lower at 80 degrees C than at the lower temp.