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Cracks in structural steel were retarded or even stopped when fatigued in aerated seawater environments at 10 Hz. Backface strain measurements proved that the cause was corrosion product wedging, which enhances the effect of crack closure. The wedge thickness depended on the oxygen supply inside the crack. This is enhanced by acration and solution pumping, which was more effective at higher frequencies.

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The stress corrosion cracking (SCC) susceptibility of six different types of stainless steel (AISI 304, 316 and 431, and Uranus 50, Orion 26-1, and Orion 28-2 from Creusot Loire) was tested in concentrated magnesium chloride (MgCl2) solutions by means of the slow strain-rate (SSR) method. The effects of strain rate, chloride concentration, testing temperature, electrode potential of the specimen, and the presence of inhibitors have been investigated. Test results are compared with literature data. The ferritic steel Orion 26-1, expected to be immune to SCC, was found to show some susceptibility in SSR tests. In the present SSR tests, some inhibitors were found to be completely effective in preventing SCC in MgCl2 solutions in concentrations considerably lower than reported in the literature for constant strain-type testing conditions.

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