The deterioration behavior of five different paints of epoxy, phenol, polyester, polyurethane, and polyvinyl chloride resins in 30% aqueous acetic acid solution at 40°C was investigated by infrared absorption spectroscopy, electrochemical impedance and glass transition temperature measurements. The absorption of acetic acid solvent was not correlated with the lowering of paint film resistance. Their Tg values were increased with immersion time because of the degree of crosslinking. High paint film resistance of phenol and epoxy resin paints was kept for a long time in comparison with those of the others. The corrosion protective property of phenol and epoxy resin paints was superior to that of the others under these conditions.

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The relation between the corrosion behavior and conditions for solution treatment of type 304 and 303 stainless steels was investigated by using electrochemical means and the measuring corrosion loss in acidic and chloride solutions. The corrosion resistance of MnS inclusion and the matrix depended on solution treatment conditions. For example, MnS and matrix treated at 1050°C dissolved with great facility, but those treated at 1300°C and 1400°C rarely or never dissolved in corrosive environments, 5% sulfuric acid solution at 30°C and 10% ascorbic acid solution at 40°C. However, in a highly corrosive environment such as boiling sulfuric acid solution, in which the δ phases formed at high temperatures, 1300°C and 1400°C were dissolved without difficulty and preferentially, the effect of the high temperature treatment on the improvement of corrosion resistance was not sufficient. In 3% NaCl solution at 30°C, pitting potential of the steel treated at high temperature had tendency to become noble remarkably. One of the greatest reason why the steel treated at high temperature has excellent corrosion resistance is that the dissolution resistance of MnS is increased. This is attributable to that the Cr content in MnS becomes larger with increasing solution treatment temperature.

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In order to predict the safe life of corrosion fatigue under randam loading conditions as are found in service, the fatigue crack propagation properties of high strength steel of HT 80 were studied both in air and in 3% NaCl aqueous solution by using the newly developed variable loading ΔK decreasing test method. The results showed that the acceleration of crack propagation was observed both in air and in 3% NaCl aqueous solution at low ΔK regions when the overload was applied to the compressive direction frequently. The effect of load frequency on the crack propagation rate in 3% NaCl aqueous solution became smaller as the frequency of variable loading increased. The effect of variable loading frequency on the crack propagation rate in 3% NaCl aqueous solution became smaller as the load frequency decreased. The mechanism of acceleration of crack propagation under veriable loading conditions was discussed based on Neumann's model.

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The corrosion behavior of Ni-Cr-P-C alloys in which the Ni/Cr atomic ratio was fixed to unity was studied in connection with metallurgical structure by electrochemical measurement and X-ray diffraction. The Ni-Cr alloy was vitrifiable by the addition of 12 at% phosphorus, but was not by single addition of carbon. In 6N HCl at 30°C, both conventionally cast and melt-spun crystalline Ni-Cr alloys had low corrosion potentials less than -300mV (SCE) and showed high anodic current density of the order of 10³ to 10⁴A/m² by anodic polarization. Once they were vitrified, they passivated spontaneously in the same aggressive solution and showed excellent corrosion resistance. The corrosion resistance of amorphous alloys was largely deteriorated even by a small amount of crystalline phase precipitation.

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The actual states of corrosion of steel structures in marine environments based on field investigations are introduced. Especially the states of intensive corrosion under mean low water level and the conditions in which such corrosion has a tendency to occur are shown. And the design of corrosion control methods is reviewed.

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