The initiation of corrosion fatigue cracks and localized corrosion were investigated metallographically on HT50-CR (controlled rolling) steel by testing with rotating beam fatigue machine in artificial sea water. Two types of localized corrosion, i. e., pitting and grooving, were observed on the specimen surface. The grooving sites were restricted to the center region of the received plate-steel. Quantitative metallographic data of pit distribution indicated that the pit growth rate in this region was significantly faster than that in the other region (surface region of received steel). It was also observed that many cracks nucleated at the grooving. Degenerate or bainitic pearlite and elongated inclusions (MnS) were contained in this region. The preferential dissolution of ferrite around the degenerate pearlite and MnS resulted in the development of pitting and grooving corrosion. An electrochemical measurement showed that the surface region was more noble than the center region and the potential difference between them was large enough for formation of macro-cell.
From these results, the relations among localized corrosion, initiation of crack and inhomogeneous structure of the steel are discussed.

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Corrosion fatigue tests were conducted in synthetic sea water to investigate the influence of flow rate on crack growth behavior in various corrosion potentials for HT80 steel. The effect of increasing flow rate under free corrosion potential was to increase the cathodic reaction rate of dissolved oxygen reduction and results in increase of crack propagation rate. When the potential was controlled electrochemically by a potentiostatt at -450mV (vs. Ag/AgCl), it showed different mechanisms with respect to flow rates. At low flow rate, two mechanisms can operate in series with testing time. The first one is hydrogen embrittlement mechanism, which become possible to occur at the crack tip with low pH. After this process, the crack propagation rate decreases with the decrease of effective stress intensity range caused by cumulated corrosion products in crevice after long test period. On the other hand, at high flow rate, the same mechanism as free corrosion potential test governed the crack propagation rate high. In the case of -523mV (vs. Ag/AgCl) test, both low and high flow rates made no difference in crack propagation rate. This result was considered that the impressed current density at low flow rate was high enough to maintain the high crack propagation rate.

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Depending on the experimental results that the current density at the cathodic polarization break had a good correlation with soil resistivity, the criterion was formulated as a relationship among critical pipe-to-soil potential required immediately after applying cathodic protection current for providing complete catholic protection, soil resistivity, coating thickness and an exposed surface area of coating holiday.

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Five different types of copper or zinc complexing agents as water-soluble dezincification inhibitors for 70/30 brass were tested by using a potentiostatic acceleration technique in 0.5M NaCl solution containing an acetic acid-sodium acetate buffer solution of pH 4.43 at 60°C. Effectiveness of the inhibitors for preventing anodic dissolution of copper and zinc from 70/30 brass was in the following order; phytic acid<octylhydroxamate potassium salt<thioglycolic acid<dimethyldithiocarbamic acid sodium salt<benzotriazole. The inhibition mechanism of these inhibitors is probably due to the formation of copper and/or zinc complex films on the alloy surface. It is concluded that an addition of the most promising inhibitors such as benzotriazole to corrosive environments is an alternative method to prevent dezincification attack of 70/30 brass.

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Stress corrosion cracking was found in Type 304 steel tank for hot water with Cl^- content of 19ppm and temperature of 80°C. It was learned that poor penetration in butt welding left a gap of 40μm in the tank wall, which would behave as a corrosion crevice to initiate cracks under residual stresses.

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As a result of the development and the advances in vacuum technology, it was possible in the early 1960's to obtain clean vacuum systems which could achieve pressures to 10^-10 torr. At these pressures it is possible to obtain and maintain atomically clean surfaces. Shortly after the development of vacuum science and technology in the early 1960's, surface analytical tools became available for analyzing and characterizing surfaces. With the combination of a good vacuum system and analytical surface tools, it is now possible to characterize and analyze surfaces in corrosion science very carefully. The object of this review is to introduce the nature and the basic mechanism of operating the surface analytical tools include (1) AES, (2) ESCA, (3) SIMS, (4) LEED and (5) FIM.

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