ABSTRACT
A plate heat exchanger with plates made of two high-alloy stainless steels and a nickelbase alloy has been tested at different temperatures using chlorinated sea water (2 ppm continuous chlorination) as the coolant. The superaustenitic 6Mo steel 254 SMO® (UNS S31254) and the nickel-base Alloy C-276 (UNS N10276) suffered crevice corrosion at 45°C which was the lowest temperature investigated. The superaustenitic 7Mo steel 654 SMO® (UNS S32654) was completely resistant even at 70°C, which was the highest temperature tested. Three laboratory tests were evaluated in terms of their correlation to this practical result. Conventional plate coupons, made of the same alloys and equipped with muliple crevice assembly (MCA) washers, were also exposed in the 45°C water. However, the results of this test were not in accordance with the results of the heat exchanger test and cannot be used for predictions. The critical pitting (CPT) and crevice corrosion (CCT) temperatures of the plate materials were determined in 6% ferric chloride. Only the CCT values show promise for prediction of the behaviour in a plate heat exchanger.
