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The occurrence of stress corrosion cracking (SCC) from crevice corrosion sites was studied using a kind of occluded U-bend specimen of Type 316L (UNS S31603) stainless steel. It was done in 0.5 M NaCl solution at room temperature and 50 8C. The galvanostatic and potentiostatic polarization methods were adopted. It was found that a tight crevice and high polarization current were the necessary conditions for SCC to occur relative rapidly from crevice corrosion sites. Meanwhile, if there was obvious SCC developing from a crevice corrosion site, the IR drop (or solution resistance) in the crevice path would increase. The increase of IR was attributed to the corrosion product deposition and/or hydrogen bubbles evolved from the cracks. On the other hand, the usually high aspect ratio of stress corrosion cracks, i.e. the inhibited dissolution on the crack walls, might be explained as due to the existence of high IR drops in them.

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Stress corrosion cracking (SCC) from crevice corrosion sites had been found in an experimental work at polarization potential of þ 200 mV SCE . In that work, an occluded U-bend specimen of Type 316L (UNS S31603) stainless steel was used. The testing was done in sodium chloride (NaCl) solution. Based on that work, the practical possibility of SCC from the occluded U-bend specimen was described theoretically. It was shown that it would also be possible for SCC to occur in practice (i.e. at practical corrosion potential), but the crevice needs to be tighter. Meanwhile, it would take a longer time for obvious SCC to emerge. For a practical crevice usually formed by placing a crevice former on a large uniform metal surface, the crevice geometry may have little effect on SCC although the crevice can sustain an acidified solution more easily than pitting. The possibility of SCC should mainly depend on the corrosion system itself, i.e. material and environment.