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.