In order to evaluate test methods of the stress corrosion cracking susceptibility of stainless steels, effects of a alloy composition on the susceptibility were examined mainly in chloride solutions of low concentration at temperatures from 150 to 250°C by using three-point loading method, and the results were compared with those in high concentrations. The following results were obtained: (1) Higher temperatures and higher oxygen concentrations increased the stress corrosion cracking susceptibility in 0.13% NaCl solution. The data at 250°C plotting the relationship between Ni and Mo contents showed that 2 to 3% Mo increased the susceptibility of alloys containing less than 35% Ni. (2) The stress corrosion test results in boiling 42% MgCl₂ solution at low and high stress levels corresponded to those in 0.13% NaCl solutions at 250°C containing 8 and 20ppm of dissolved oxygen initially. These correspondences were explained by the stress corrosion mechanism in those solutions. (3) The stress corrosion test results of 18Cr-13 Ni-3Si stainless steels containing 0.02 to 0.07% C and 0.01 to 1.0% Cu in various chloride solutions were influenced by test environments and stress loading methods. However, the stress corrosion cracking susceptibility was generally improved by high contents of carbon and copper.

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In our previous reports, we concluded that active sites on metal, where two types of organic corrosion inhibitors could be adsorbed, were anchored with two types of water, one by its electron donation and the other by its proton donation. When the water was desorbed, electron-accepting sites and proton-accepting ones would be revealed on metal. Electron-donating species, such as RN (CH₃)₂ (or ROR'), could be adsorbed by displacing the water only on the electron-accepting sites, while those species which could act as proton donors and as electron donors, such as RNH₂ (or ROH), could be adsorbed on both sites.
In the present work, investigation on the electron-accepting sites was mainly carried out in non-aqueous media. Hydrogenation of olefines with Ni-catalysts was most promoted by the addition of the limited amounts of tertiary amine (10^-5M/g-metal) and by further addition it was retarded because of poisoning Ni. Ni powder was acceleratedly corroded by alkylhalides with the amounts of the amine and further addition over the amounts inhibited the corrosion. These acceleration should take place, as the water anchored by its electron donation was forced to depart from metal surface by the amine exposing electron-accepting sites. When the electron-accepting sites were again adsorbed with electron-donating species such as tertiary amine, corrosion inhibition would be made up. When the sites were exposed to reactants such as olefines or alkylhalides because of insufficient amounts of the amine, the catalytic hydrogenation or the corrosion would easily take place.
With primary amine, reproducible results as presented with tertiary amine could not be obtained. For these phenomena, it is supposed that primary amine can be adsorbed by two ways differing from the case with tertiary amine and conflicting data will be brought about.

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