X-ray photoelectron spectroscopy has been used to investigate the effect of the composition of surface films on their protective properties. Amorphous cobalt-chromium alloys passivate by the formation of a certain amount of hydrated chromium oxy-hydroxide in their films. The open circuit corrosion resistance also depends upon the concentration of hydrated chromium oxy-hydroxide in corrosion-product film, despite the fact that the corrosion potential of the alloys is in the active region. The surface film formed on Co-Cr-20B alloys contains a large amount of borate together with hydrated chromium oxy-hydroxide, whereas the passive film formed on corrosion-resistant amorphous Co-10Cr-20P alloy by spontaneous passivation consists exclusively of hydrated chromium oxy-hydroxide. The presence of a large amount of borate in the surface film increases the corrosion rate and is detrimental for passivation.

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A probability statistical approach to pitting corrosion life prediction was discussed in order to bridge the gap between laboratory and field data. It has been demonstrated that probabilistic approach is required for quantitative evaluation of pitting corrosion data. A probabilistic model of pitting corrosion was presented, which is analogous to the stress-strength model in reliability analysis. In this model, pitting corrosion takes place when the probability distribution function of the pitting corrosion propensity of the environment and of the pitting corrosion resistance of the material overlap. It was shown that a reliable estimation of the pitting corrosion depth of a product can be made by means of the extreme value probability plot of the experimental data obtained for numbers of small specimens. Log-log plots of the estimated maximum pit depth against time yielded a linear relationship for pitting corrosion of aluminum with a slope of 0.5, which agreed with the results of the log-log plots of the published long term pitting corrosion data of aluminum. It was suggested that extrapolation of this line to the expected corrosion life of the product or the thickness of the metal used yielded the pitting corrosion life of the product.

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The rate of hydrogen absorption in cathodically polarized zirconium was measured by using the differential etching method, in which the specimen covered with hydride was dissolved layer by layer from surface in hydrofluoric acid solution containing hydrogen peroxide, and the volume of liberated hydrogen was determined with a gas burette. Sigmoid in-depth hydrogen concentration profile was obtained with this technique and the results were ascertained both by the methods of the (d, n) reaction and the mass spectrometric measurement. Total amount of absorbed hydrogen and the thickness of hydride layer were estimated respectively by the integration of the profile and the determination of the profile front. In general tendency, the linear and the parabolic rate laws were held before and after the absorption reached at the level of 0.3 NTP cm³/cm² respectively. The existence of alkaline salt in the electrolyte stimulated the absorption, and abnormally high surface hydrogen content in the hydride layer was observed. Under the condition of galvanostatically cathodic polarization the maximum absorption was obtained at pH=7 in any kind of electrolyte. The mechanism of absorption process was discussed on the basis of the kinetic relations among the intial rate of absorption, the electrolytic current and the electrode potential.

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Based upon linear elastic fracture mechanics approach, a damage tolerance design philosophy for light water reactor pressure vessel and piping components where the presence of a significant crack is acceptable, was reviewed with special reference to stress corrosion cracking and corrosion fatigue subcritical crack growth.
The published data of failure analysis were discussed from a viewpoint of fracture mechanics evaluation. Here, weld toe cracking in crude oil pipe-lines in Canada, and corrosion-pit initiated cracking in low pressure turbine discs at Hinckley Point ‘A’ and turbine shafts at Ferrybridge power stations in England were compared and discussed. Hence three parameters such as mechanical, metallurgical and environmental factors are taken into consideration.

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