Influence of heat treatments between 400 - 750°C on the corrosion resistance of duplex 329 stainless steel

Ageing for 1 h at 500-650 degree C slightly sensitized the alloy to intergranular corrosion. Only the electrochemical potentiokinetic reactivation method (EPR) was capable of distinguishing between mildly sensitized and unsensitized specimens. The overall corrosion resistance was decreased by heat treatments in the range 500-650 degree C. An abrupt decrease in pitting potential values and an increase in pit dimension and density were observed in polarization tests and galvanostatic pitting experiments. The average corrosion rates calculated from weight loss on as-received and aged samples after immersion in sulfuric acid and ferric chloride solutions were in agreement with previous findings.