ON-LINE HIGH TEMPERATURE ELECTROPHORESIS TECHNIQUE FOR EVALUATING STRESS CORROSION CRACKING RISK OF STAINLESS STEELS IN COOKING PROCESS

摘要

On-line high temperature capillary electrophoresis instrument (HotUCE) was constructed for analysis of corrosive ions at normal pulping process temperatures in synthetic liquors in order to evaluate stress corrosion cracking (SCC) susceptibility of stainless steels. The HotUCE-instrument was on-line coupled to an autoclave, where welded duplex stainless steel samples were immersed 500 h in the simulated high ionic strength hot black, hot white or green liquors at temperatures below 210ºC. The results showed that only minor amounts of oxidized sulphur compounds emerged. Amounts of sulphur species correlate with the corrosion potential changes of the duplex stainless steel specimens during the cooking experiments. The increase of sulphite during cooking was higher in hot white than in hot black liquor. The results indicate that SCC risk was enhanced at higher temperatures most probably due to increased formation of thiosulphate.