Local Corrosion Behavior Of Stainless Steel Weld Joint In Alkaline Catalytic Solution Of Sulfur Recovery

This paper investigated the local corrosion behavior and stress corrosion behavior of 304 base metal,304 weld joint,316 L base metal and 316 L weld joint under a various range of temperature and sulfur contents by using weight loss experiments,classical electrochemical measurements and slow strian rate tests.The main reseraches and results are as followed:(1)The average corrosion evaluations of 304 base metal,304 weld joint,316 L base metal and 316 L weld joint in alkaline catalytic solution of sulfur recovery showed that they had good general corrosion resistance.However,the pitting corrosion in some local areas still posed corrosion risks on their property.The pitting corrosion resistance reduced with the increase of sulfur contents ranging from 0 g/L to 2 g/L and then under the stress concentration of weld joint and external environment,the crack originals induced by pitting corrosion had risk of stress corrosion.The pitting corroison resistance are as followed: 316 L base metal >304 base metal > 316 L weld joint > 304 weld joint.(2)The results of electrochemical tests of 304 base metal,304 weld joint,316 L base metal and 316 L weld joint in alkaline catalytic solution of sulfur recovery showed that their pitting corrosion resistance were basically in accordance with their SEM graphs of weight loss experiments.Therefore,the pitting corroison resistance are as followed: 316 L base metal >304 base metal > 316 L weld joint > 304 weld joint.(3)The results of slow strain rate tests of 304 base metal,304 weld joint,316 L base metal and 316 L weld joint in alkaline catalytic solution of sulfur recovery showed that the sulfur increased the risks of stress corrosion.Besides,the 304 weld joint had greater possibility of stress corrosion than 304 base metal and so did 316 L.Furthemore,Under the cathodic protection potential ranging from 0 to 200 m V,the stress corrosion resistance of 304 base metal,304 weld joint,316 L base metal and 316 L weld joint increased initially to a peak and then decreased.The best cathodic protection potential was-100 m V.(4)Generally,in alkaline catalytic solution of sulfur recovery,304 base metal and 316 L base metal had trends that the sulfur induced the pitting corrosion initially and then the pitting corrosion induced crack originals to accelerate the stress corrosion.The pitting corrosion resistance and stress corrosion resistance of 304 weld joint and 316 L weld joint were lower than those of base metal.Therefore,applying the approporiate cathodic protection potential could reduce the possibility of local corrosion failure of 304 and 316 L.