Parametric optimization of DL-EPR technique for evaluating IGC susceptibility of 316LN type stainless steel using the Taguchi method

By using the Taguchi method with an L-16 (4(5)) orthogonal array, the conditions of the double loop electrochemical potentiokinetic reactivation (DL-EPR) technique have been optimized to evaluate the different degrees of the precipitates among the sensitized AISI 316LN austenitic stainless steels. The optimum conditions under the highest resolution of DL-EPR were approved to be 1.2M sulfuric acid, 0.05M potassium thiocyanate, 0.8M sodium chloride, 40mV/min scan rate, and 40 degrees C. Analysis of variance (ANOVA) was used to determine the effect of the control parameters on the degree of sensitization (DOS) difference. As a result of ANOVA, the sulfuric acid concentration had the most significant effect on the DOS difference among the five factors. The percent contributions of sulfuric acid (H2SO4), potassium thiocyanate (KSCN), sodium chloride (NaCl), scan rate, and temperature to the DOS difference were 53.22, 5.33, 21.74, 4.92, and 14.79%, respectively. Finally, the maximum DOS difference (6.7908) obtained from the confirmation experiment showed an approximate 11 times improvement.