Abstract
The austenitic (AISI 300 series) stainless steels are highly susceptible to chloride stress corrosion cracking. This work was undertaken to define conditions under which hydrochloric acid can be used safely for chemically cleaning equipment containing these steels.
The active-passive characteristics of the alloys play an important role which probably has not been understood previously. A number of factors, acting together, must be present to produce cracking. Indications are that cracking occurs in neutral chloride solutions, when passivity is destroyed at localized areas of film break-down. If the entire surface is activated, as in the presence of hydrochloric acid, no cracking will result.
The data were obtained by tests on horse-shoe type specimens, statically stressed to 75 percent of yield strength. Specimens in the annealed, cold rolled and sensitized conditions were used to simulate conditions likely to be encountered in alloys in the “as fabricated” condition. Exposures were made in 5 percent hydrochloric acid solutions to simulate cleaning conditions. Other tests were made in dilute neutral chloride solutions at 400 F to simulate operation after cleaning.
The problem of design is considered, as is proper selection of alloy types, especially if welding is to be performed during fabrication. 3.2.2
