Corrosion of Stainless Alloys in a Chlorine Dioxide Bleached Pulp Washer, 1991 Engineering Conference Proceedings

The general and crevice corrosion resistance of 44 stainless alloys was investigated by coupon testing in a chlorine dioxide washer vat. Sodium hydroxide is added before the vat to maintain vat pH between 6 and 7. Practically all the alloys tested experienced corrosion in this hot, oxidizing, chloride-containing, near-neutral environment. Nickel-base (>50% Ni) alloys were resistant to crevice corrosion, but experienced pronounced general corrosion thinning due transpassive dissolution. The high-nickel (30-50% Ni) alloys and the austenitic, superaustenitic, duplex and superduplex stainless steels suffered crevice corrosion, but were resistant to general corrosion.

The superaustenitic stainless steels were on average no better in terms of maximum depth of crevice penetration than type 317L austenitic stainless steel, the former "standard" material of construction for bleach washers. Despite their appreciably lower alloy content, the duplex and superduplex stainless steels were on average better in this regard than the superaustenitics. The higher LCR (Localized Corrosion Resistance) alloys within each family tended to have superior resistance to crevice corrosion. The nickel-base alloys had the best crevice corrosion resistance, although their susceptibility to general corrosion thinning precludes their application in this service.