Recently, austenitic stainless steels are generally used for the material of atomic reactor's heat exchangers. But stress corrosion cracking of stainless steel heat exchangers under condition of high temperature water has been reported. So we have made some experiments to study the stress corrosion cracking of stainless steel heat exchangers in high temperature water.
The results obtained are as follows:
(1) Cold drawing of stainless steel tubes and existence of chloride ion and dissolved oxygen in water accelerate the occurrence of stress corrosion cracking.
(2) Seal welding by TIG method between the tube plates and the tubes accelerates the crack initiation.
(3) Solution treatment of cold drawn stainless steel tubes decreases the sensibility to stress cracking.
(4) The eddy current method is effective for nondestructive inspection of stress corrosion cracking in expanded parts of stainless steel heat exchangers.

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8-oxyquinoline, N-methyl-N-cetyl-2-ethanolamine, N-methyl-N-cetyl-3-propanolamine, of which hydrogen-bonds lie between N-atoms and hydroxy groups, were used as intramolecularly hydrogen-bonded inhibitors and N-methyl-N-propyl-cetyl-amine and N, N-dimethyl-cetylamine were used as unbonded references.
Presence of the intramolecular hydrogen-bond was determined by infrared spectra of these inhibitors dissolved in carbon tetrachloride. Meanwhile weight-loss of mild steel test coupons prefilmed with these inhibitors and dipped in uninhibited 5% HCl aqueous solution were measured.
Inhibition efficiencies of the intramolecularly hydrogen-bonded inhibitors were shown to be lower than those of the unbonded, since an unshared electron-pair which was necessary for chemisorption of the inhibitor on metal surface was blocked by hydrogen-bond. Dilution of the inhibitor solution or elevation of the filming temperature was not effective for dissociation of these intramolecularly bonded inhibitors whereas it could dissociate the intermolecularly bonded one. Therefore, the inhibition efficiencies of the intramolecularly hydrogen-bonded inhibitors showed milder increase than that of inhibitor concentration of the filming solution or than the elevation of the filming temperature.
Addition of proton acceptors such as dioxane to the intramolecularly hydrogen-bonded inhibitor could keep the unshared electron-pair of N-atom free from blocking of the hydrogen-bond by forming intermolecular hydrogen-bond between hydroxy group of the inhibitors and oxygen atom of dioxane. By adding dioxane to the filming solution, therefore, the efficiency of the intramolecularly hydrogen-bonded inhibitor became higher than that of the unbonded inhibitor.
When a proton donor like acetic acid was added to the filming solution, the intramolecularly hydrogen-bonded inhibitor was associated with the proton donor and high inhibition efficiency was observed because associated molecule thus formed was more adsorbable on metal surface.

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