DISSOLUTION OF STAINLESS STEEL UNDER ALTERNATING CURRENT POLARIZATION

Abstract

The present work studies the dissolution of stainless steel electrode (12X18H10T) under alternating current polarization with frequency of 50 Hz in sulfuric acid solution. The impact of the current density (200-1200 A/m(2)) in a stainless steel electrode, the current density (20-120 kA/m(2)) in a titanium electrode, a concentration of sulfuric acid solution (0,25-1,5 M), an electrolysis duration (0,25-1,5 hours) and an alternating current frequency (50-250 Hz) on the electrical dissolution of an alloy based on iron-chromium were investigated. The preliminary studies have shown that alloys do not practically dissolve under the polarization of two stainless steel electrodes by the alternating current. And, when one of the stainless steel electrodes is replaced by a titanium wire, the alloy dissolves intensively with the formation of Fe2+,Fe3+,Cr3+ and Cr6+ ions. This can be explained by the valve property of the titanium electrode. Under the direct current polarization, the alloy dissolution at a very low current efficiency was observed (12.7% for general iron ions, 3.9% for general chromium ions). As the current density in the stainless steel electrode increased up to 400 A/m(2), the dissolution rate of the alloy reached a maximum value (84% for general iron ions and 17% for general chromium ions). The optimum current density of the titanium electrode was detected; at a density of 60 kA/m(2), 54% of the current efficiency is formed by iron ions while 15% by the total chromium ions. At a sulfuric acid concentration of 0.5 M, the stainless steel electrode dissolution showed the maximum value. It has been established that, as the duration of electrolysis and the frequency of alternating current increase, the current efficiency of the stainless steel electrode dissolution decreases.