The effects of 0.5 mmol L^－1 sodium molybdate and 0.5 mmol L^－1 aluminum lactate on the corrosion of steels under 10 mmol L^－1 NaCl solution layers were investigated. Electrochemical measurements were carried out using a siphon cell to form solution layers of 0.2 mm-1.0 mm thickness on the samples. From the potentiodynamic polarization measurements, the diffusion limiting current, j_lim and the anodic current, j_anode were measured and the changes by the effects of the corrosion inhibitor were evaluated. There was no change of j_lim, while j_anode decreased, indicating that used inhibitors reduced the anodic reaction rate. From the electrochemical impedance measurement results, impedance behavior under the solution layer was different from that in the bulk solution, and it was suggested that the protective layer structure changed with the quantity of solution.

Effects of temperature on electrochemical behavior of aluminum alloys and carbon steel were investigated in aerated 20 mass％ NaCl solutions at sub-zero temperatures. Rest-potentials of carbon steel shifted to positive direction with decreasing temperature, which of aluminum alloys were unaltered with temperature. Clear oxygen diffusion limiting current densities were observed in all the experimental conditions. The limiting current changes are in the order of A6061＜A1050＜carbon steel. The oxygen limiting currents of carbon steel decreases slightly with decline of temperature, which of Al alloy are independent of temperature. Electrochemical impedance spectroscopy （EIS） results of carbon steel implies that EIS behavior changes with temperature.

For safe and stable operation of chemical plants, we studied the implementation of artificial intelligence to determine and evaluate damage mechanisms for damage of non-metallic materials. Existing damage cases of non-metallic materials were collected, data cleansing was performed, and decision tree analysis was conducted. In addition, the presence or absence of over-learning was also examined. As a result, with a certain number of cases, it is expected to be possible to extract conditions for determining the damage mechanism and to predict possible damage for mechanisms.

In order to clarify the effect of W on suppression of paint blistering and its mechanism, analysis of rust formed on W bearing steel by corrosion test, and verification experiments such as an artificial synthesis Fe₃O₄, measurement of membrane potential of rust films and electrochemical measurement were conducted. As a result, W refines Fe₃O₄ particles which are main components of rust under paint film, and gives rust cation selective permeability. Both effects prevent corrosion factors from reaching the surface of substrate. In addition, W forms insoluble oxides and prevents Fe dissolution by inhibitory effect. These effects suppress Fe corrosion and the formation of rust, thereby suppressing paint film blistering.

The effects of chloride ion, acetate ion and Mo addition on the depassivation pH （pH_d） of martensitic stainless steel were investigated using anodic polarization measurement and surface film analysis （XPS）. The increase of chloride ion concentration promoted partial destruction of the film and obscured the transition from active state to passive state. The increasing of acetate ion concentration increased the pH_d and acted as a negative factor for passivation. It is considered that the addition of Mo lowered the pH_d and promoted the formation of passivation film in a high-concentration acetic acid environment.