Evaluation of voltametric profiles for quantitative estimation of sigma phase (σ) content in duplex stainless steel UNS S31803: an ohmic and layers porous resistance models (LPRM) analysis

The voltammetric profile parameters of potential and peak current intensity, for different scan rates were obtained for heat treated duplex stainless-steel samples. The Ohmic and Layer Porous Resistance models were considered for quantitative estimation of deleterious phase surface content (sigma phase). A 4 mol L-1 KOH selective solution and a specially designed electrolytic cell were used. The observed linear slope for vs and Ip vs linearity profiles are in accordance with the considered LPR Model. The parameter profile of peak potential (), with the square root of the scan rate (1mV s-1, 2 mV s-1, 5 mV s-1, 7 mV s-1 and 10 mV s-1.), suggests the growth of a film rich in Fe and Cr content that could be correlated to the sigma phase level with the dependence of on scan rate been considered a better parameter, than peak current, for detect small levels of sigma phase for a specific scan rate. The non-dependence of from surface area, make it a more feasible parameter for a lower sigma phase level quantitative analysis.