This investigation was made to evaluate the inhibiting effect of mercaptobenzothiazol (MBT) on the corrosion of copper and brass in non-oxidizing acid solution containing oxygen or oxidizing agent such as Fe³⁺ or Cu²⁺. The results obtained are as follows.
(1) MBT gives good inhibition to the corrosion of copper and brass in HCl, H₂SO₄ or H₃PO₄ each containing oxygen. But the requisite concentration for good inhibition in HCl is higher than in H₂SO₄.
(2) Under the existence of Fe³⁺, the corrosion nhibiting effect of MBT for copper and brass in H₂SO₄ is excellent, but in HCl it is less effective than in H₂SO₄. In H₃PO₄ containing Fe³⁺, the inhibiting effect of MBT for brass is excellent, but the effect for copper is insufficient and is similar to the effect in HCl.
(3) Also, MBT gives good inhibition to the corrosion of copper and brass in H₂SO₄ or H₃PO₄ both containing Cu²⁺.
Furthermore, the inhibiting mechanism of MBT for the corrosion of copper in H₂SO₄ or HCl has been studied by the polarization characteristics.

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The corrosion of iron-chromium alloys containing 0-30% Cr in maleic acid solution was investigated. The results were summerized as follows;
(1) An increase in chromium content had a favorable effect on the diminition of the active current density of the alloys. The similar results had been found in sulfuric acid and concentrated alkaline solution.
(2) The anodic dissolution and the corrosion weight loss became larger, as the concentration increased and temperature rose.
(3) The logarithms of time and initial current density necessary for the onset of passivity of iron showed straight-line relation.
(4) The formation of the order lattice (Fe₃Cr) in the alloys was found to be responsible for a remarkable anodic dissolution.

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The corrosion of austenitic stainless steels and titanium in the aqueous solutions of several amino acid and their salts was investigated. The total immersion tests, the cell voltage-current curve method and the potentiostatic polarization curve method were adopted.
The following experimental results were obtained: The aqueous solutions of acidic amino acids such as glutamic acid or homocysteic acid were comparatively corrosive, while neutral and basic amino acids scarcely; the corrosive behaviors of acid and basic salts of various amino acids bore some resemblance to those of acids and bases which were estimated to be freed from the salts.
It is suggested that amino acids, which form salts with acids or bases, might have some neutralizing action on them, resulting in reduction in the corrosive effects of these salt solutions.

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