The relationship between corrosion weight loss and weight of surface corrosion products of hot-dipped galvanized steels, in a coastal area has been studied to estimate corrosion rates. The weight of surface corrosion products was shown to increase almost in proportion with corrosion weight loss. Therefore corrosion weight loss of galvanized steel articles used in coastal areas can be estimated by measuring the weight of remaining corrosion products. Thus, corrosion rates can be easily obtained without special atmospheric exposure tests or measurements of corrosion factors in the environment.

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Stress corrosion cracking behavior of nickel containing 13Cr martensitic stainless steels was examined in high temperature-high purity water. Nickel content was varied from 0 to 5.7wt%, while carbon content was varied from 0.024 to 0.31wt%. The steels were tested under slow strain rate test (SSRT) conditions in high purity water of 8ppm dissolved oxygen (DO) in the temperature range of 50-288°C. SCC susceptibility peaks at temperature of 150-250°C. This may be ascribed to chemical stability of the surface film formed in this temperature range, being independent of cracking forms such as active path corrosion (APC) type and hydrogen embrittlement (HE). Active path corrosion type cracking tends to initiate at corrosion pits on the free surface, while seldom occurs in the crevice and inside the casting defects. This may be owing to the fact that APC susceptible potential lies in a rather noble potential range such that the free surface shows. Furthermore HE does not occur even when the corrosion potential of the creviced surface reaches hydrogen reduction potential unless stress concentration or film breakdown is induced by pitting. Thus HE susceptibility does not appear to increase. Low Ni and C containing steel subjected to high temperature tempering is immune to SCC and this steel may be concluded to be highly resistant to SCC judging from severe stress conditions given under SSRT conditions.

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Electrochemical noise generated from corrosion potential of Type 304 stainless steel in MgCl₂ solution has been studied by using a FFT analysis. White noise was observed in a frequency range below 0.1Hz and hence PSD at 0.05Hz was used as a measure for a noise power of the system. PSD at 0.05Hz was found to change as a function of the concentration of MgCl₂, temperature and immersion time. The slope of the log(PSD) vs. log(t) line was correlated with the kinetics of the film formation, by assuming that corrosion velocity is proportional to PSD.

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The effects of alloy elements in aluminum alloys on the corrosion preventive layer prepared by the chemical conversion with dilute solutions containing MgSO₄ and NaHCO₃ were investigated. Both A 5052 and A 7072 were resistant to a dilute NaCl solution containing cupric ions, similar to pure aluminum (99.99% Al), when they were pretreated to obtain the protective film. The alloy elements, Mg in A 5052 and Zn in A 7072, existed as the solid solution. On the other hand, Cu in A 2017 and Mn in A 3003, may form the intermetallic compounds such as CuAl₂ and (Fe, Mn)Al₆, and Si in BA 4045 forms an eutectic mixture. The films on A 2017, A 3003, and BA 4045 were poor, and hence the resistivity to pitting was insufficient.

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General concepts for life evaluation of equipments operated at high temperature were described. Creep and high-temperature corrosion were focused. For the remaining creep life evaluation, three methods calculated from operation records, by accelerated creep tests and by measurments of creep deformation and creep cavities were introduced. Concerning the high-temperature corrosion, it was emphasized that fire-side corrosion of waterwall and superheater tubes in boilers using corrosive fossil fuels frequently governs the tube life. And it was introduced that carburized thickness was always monitored for life management of hydrocarbon cracking tube, since creep cracks were initiated with the stress increment induced by the carburization.

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The current major mechanisms for the adherence of oxide scales which is greately enhanced by the addition of rare earth elements, reactive elements or their oxides are summarized and critically reviewed in the light of recent experimental results. A drastically new mechanism is also examined which is based on the prevention of both segregation and concentration of a small amount of sulfur in the alloy to the scale/alloy interface.

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