The atmospheric corrosion behaviors of carbon steel have been studied by one-year exposure test in urban, Phnom Penh, and marine, Sihanoukville, atmospheres in Cambodia. The morphology, crystalline phase, and the cross-sections of corrosion product were characterized. The annual corrosion rates in Phnom Penh, and Sihanoukville was approximately 9 μm y^-1 and 27 μm y^-1, respectively. According to the category of corrosivity classification ISO 9223, Phnom Penh is classified as a low corrosive atmosphere （C2 category）, while Sihanoukville is classified as the medium corrosive atmosphere （C3 category）. The severe corrosion attack in Sihanoukville resulted from the airborne salinity, which contained higher concentrations of Cl^- in this marine atmosphere along with the longer time of wetness, while the Phnom Penh atmosphere contained less chemical species with a short time of wetness. The formation of rust layer in the Phnom Penh was more adherent and compact than that in Sihanoukville thus the corrosion resistance of metal in the Phnom Penh was higher than that in the Sihanoukville atmosphere.

UCL tests were performed in hydrogenated steam to accelerate SCC initiation in PWR Primary water environment. Although surface finishing effect on SCC behavior has been discussed by many researchers, it remains unresolved. The surface finishing effect on the test results was investigated by using two types of UCL specimens. One specimen was polished by the emery paper （emery polished） and the other was polished the emery paper and OP-S （mirror polished）. UCL tests were interrupted every 450 hours. Some micro cracks whose length is less than one grain boundary length were observed by SEM on the mirror polished specimen after 450 hours, but no cracks observed on the emery polished specimen after 450 hours. When cracks shorter than one grain boundary length were eliminated, time dependency of total crack number was almost the same in both the specimens up to 900 hours. After 1350 hours, total crack number on the emery polished specimen was larger than that of the mirror one. The maximum crack length of the emery polished specimen is larger than that of the mirror polished specimen. Crack volume was calculated from crack data under the assumption that crack depth and crack width were proportional to crack length. The relationship between the sum of AE energy and total crack volume suggested that crack depth in the mirror polished specimen might be larger than one in the emery specimen, or that contribution of coalescence and propagation of micro cracks in these specimens might be different.

In order to evaluate and compare the corrosion resistance of 329J3L cast steel, 329J3L rolled steel and 329J4L rolled steel, field test using sea water, immersion test and electrochemical anodic polarization test in ferric chloride aqueous solution were conducted, and inclusions in 329J3L cast steel and 329J3L rolled steel were examined with SEM/EDS. 329J4L rolled steel having the highest PRE （pitting resistance equivalent） showed the highest corrosion resistance. The corrosion resistance of 329J3L cast steel was lower than that of 329J3L rolled steel although their PRE were nearly the same. The SEM/EDS analysis revealed that the number of inclusions which could induce corrosion was much more and the size of inclusions was larger in 329J3L cast steel than in 329J3L rolled steel.

In order to clarify the applicable conditions, the corrosion resistance of SUS445 as a pipe in which 80℃ hot water flows was evaluated under the condition simulating an actual environment. In case of combination with a resin joint, pitting corrosion may occur at the chloride ion concentration of 65mg/L and more when the residual chlorine concentration is 1.0 mg/L. Same in case of combination with a resin joint, the chloride ion concentration at which pitting corrosion may occur is 110mg/L and more when the residual chlorine concentration is 0.5 mg/L. In case of combination with a brass joint, pitting corrosion may occur at the chloride ion concentration of 1000mg/L and more when the residual chlorine concentration is 1.0mg/L.

The time required for passive film breakdown, t_bd and the protective efficiency, P of an ultrathin two-dimensional polymer protective coating prepared by chemical modification of a carboxylate ion self-assembled monolayer adsorbed on a passivated Fe were measured in aerated 0.5 M NaCl. The value of t_bd was short, 1.7 h. The t_bd value of the passivated Fe electrode covered with the polymer coating and further, healed in 0.1 M NaNO₃ was 4.1 h. The P values of these coatings were extremely high, around 99.9% before t_bd, indicating perfect protection of Fe against corrosion in both solutions, unless the passive film was broken down. The P values of protective coatings prepared by chemical modification of three self-assembled monolayers adsorbed on metals and oxidized metals were compared with one another in short and long ranges of the immersion time in oxygenated 0.5 M neutral solutions.