Nitric acid solutions used were 1.0moldm^-3 for nickel and 1.5moldm^-3 for copper, zinc and brass. No particular effect of magnetic field on dissolution of nickel and zinc was observed. This is probably because nickel was not easy to be oxidized, and zinc evolved hydrogen gas so much that the nitric acid solution was violently stirred. On the contrary, influence of magnetic field on the dissolution rate was clearly noticed for copper and brass. The dissolution rate of copper was strongly inhibited above a magnetic flux density of 0.1T. The dissolution of (111) and (200) planes of copper surface was inhibited relatively. The dissolution rate of brass was affected above 0.07T. The dissolution of (020β) and (121β) planes of brass was slightly inhibited above 0.1T. In this case, dissolution rate of copper in brass was inhibited, but that of zinc in brass increased gradually with time. It seemed that the metal components which was easier to be oxidized were affected with magnetic field in case of alloy.

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Solutions were obtained using the Parkhurst's equations on the sulfide formation in gravity sewer lines based on assumptions applied to actual case studies of sewer corrosion. By assuming the presence of an oxidation layer, better known as the “Beggiator Mat”, on the surface of the sludge accumulated at the bottom of sanitary sewers, the destruction process from sulfide build-up was explained clearly. The Z-value proposed by Pomeroy for estimating corrosion damage proved to be similar to the solution of sulfide density at infinite time in the differential equation for sulfide build-up in gravity sewers. Based on the computation of the sulfide formation equations, three locations of severe corrosion were identified, that is, the turbulent flow point, the upstream flow and the downstream flow. The extent of corrosion attack at these respective locations was also estimated.

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Natural corrosion potential and bulk solution pH of Al-Fe alloys which were corroded in aerated and stirred 0.1M NaCl solution for a immersion period of 1000h were investigated in terms of electrochemical behavior. The iron of intermetallic compounds dissolved into ferrous iron. Later, the ferrous ions had changed into metallic iron, directly inside the pit, and outside through the intermediate ferrous hydroxide stage.

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Environmental effects on corrosion behaviors and properties of oxide films were evaluated for austenitic stainless and carbon steels in high-temperature water simulating a Boiling Water Reactor condition. The existence ratios of Cr and OH^- in oxide films formed on stainless steel decreased and those of Fe, Ni and O^2- increased with increases of temperature and dissolved oxygen concentration. Changes of pH in the test region did not affect the composition of these species. These results indicated that Cr tended to combine with OH^-, i. e., Cr existed as hydroxides or oxyhydroxides. Further, Fe and Ni tended to form spinel type oxides, which were identified by XRD. In addition, the corrosion resistance of stainless steel was higher than that of carbon steel in all environments. The protectivity of magnetite films on carbon steel increased with temperature, dissolved oxygen concentration and pH. However, Ni ferrite, formed on stainless steel, further improved the corrosion resistance under such conditions. On the other hand, as the solubility of magnetite increased with decreases in the above mentioned factors, the corrosion resistance of carbon steel decreased. But, even under such conditions Cr, contained in stainless steel, tended to form stable films and suppressed corrosion.

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Almost all chemical plants handle various corrosion fluids. Therefore, the metallic materials for chemical equipments are used adding corrosion allowance after be studied the adaptability and the corrosion resistance of materials, equipment corrosion life and other factors. In this report, the following items in regard to general corrosion are introduced. (1) The major standard or rules for corrosion allowance. (2) An example of corrosion life in oil refinery plant. (3) The failure instances in chemical equipments. (4) The inspection methods to nip in the bud prevent or to predict corrosion troubles.

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Extremely corrosion-resistant amorphous alloys in hot concentrated various acids, such as hydrochloric, nitric and phosphoric acids are reviewed. Amorphous alloys described are iron-, nickel-, copper- and aluminum-base alloys. The extremely high corrosion resistance is attained by alloying with valve metals, particularly with tantalum. Processing techniques of corrosion-resistant amorphous surface alloys on conventional crystalline metals by sputtering and by using laser and electron beams are briefly illustrated.

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Summarization on the corrosion behavior of stainless steels in highly oxidizing nitric acid has been undertaken, including mainly the effects of environmental and material factors on the corrosion in the trans-passive potential region. The mechanism of selective grain boundary attack in stainless steels and corrosion protection by controlling environments or corrosion resistant alloys are also described in this paper.

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