ATMOSPHERIC-INDUCED STRESS CORROSION CRACKING OF AUSTENITIC STAINLESS STEELS UNDER LIMITED CHLORIDE SUPPLY

SUMMARY: The occurrence of atmospheric-induced chloride stress corrosion cracking in types 304L and 316L stainless steels contacted with sea-salt and magnesium chloride deposits has been studied under controlled conditions of relative humidity (ca. 30%) and temperature (80°C). The time to cracking and extent of cracking are shown, at least semi-quantitatively, for specimens contacted with sea-salt deposits to be related to the deposit size prior to environmental exposure with each of these quantities appearing to decrease with decreasing deposit size. For specimens contacted with MgCl2 these quantities correlate with the nominal deposition density decreasing with decreasing deposition density. Specimens of these stainless steels, U-bends and pieces taken from an intermediate level waste container, were also exposed to a marine environment in sheltered and open exposures. Pitting and oxide build up was observed on these specimens after ca. 5 months with greater pitting occurring on the specimens exposed under the shelter. No cracking was observed in the atmospheric exposures.