Effects of additional alloying elements on electrochemical properties and corrosion resistance of Al-1% Zn, Al-0.03% In, Al-0.1% In and Al-0.1% Sn alloy rolled sheets were examined. Al-Sn alloy was the nost less-noble and the least corrosion resistant among the binary alloys. The addition of Cu, Si or Mn made pitting potential of all the alloys noble, while that of Mg or Fe gave little effect. Corrosion resistance greatly decreased with the addition of more than 0.3% Zn in Al-In alloys. Al-Sn and Al-In alloys containing a small amount of Zn can be excellent sacrificial anodes with good corrosion resistance.

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The long-term corrosion testing for the copper tubing was conducted by using the water loops simulating the conditions of the hot-water supply system in buildings. The electrode potential of the inside of the copper tube was measured against the saturated calomel electrode holding at room temperature.
In the hot-water (60°C) containing residual chlorine of 3mg/l, the potential of the copper tube exceeded the critical value for pitting (+150mV vs. SCE), after the certain induction period. The pit morphology obtained in the experiment was essentially the same as the type 2 pitting which has occurred in the actual service piping of buildings in Japan. The dosage of a small amount of Phytic acid into water suppressed the potential increase of the copper tube, even under the presence of residual chlorine, and pitting did not occur. The inner surface of the copper tube was uniformly covered with the greenish-blue precipitates consisting of copper and phytic salt. Whenever pitting occurred on the copper tube, the mounds of basic copper sulfate were formed above the pits. The unattacked area of the copper tube was covered with a mixture of copper oxide and copper orthosilicate. On the other hand, the addition of phytic acid in water prevented the formation of these compounds, and only cuprous oxide and the amorphous deposits were formed.
The maximum pit depth of the copper tube in the corrosion accelerating condition was estimated by the application of the extreme value statistical analysis. The growth of pit depth and the inhibitive effect due to phytic acid was clearly shown by the Gumbel distribution analysis.

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The behaivior of preferential dissolution of α′-martensite in Type 304 stainless steel was investigated from the standpoint of the dislocation density.
The dislocation density of α′-martensite was estimated as 1.107×10¹¹(n/cm²) from the relation between hardness and dislocation density. Dissolution rate of α′-martensite was one order of magnitude higher than that for austenite of ordinary Type 304 stainless steel. However, the dissolution rate of austenite whose dislocation density was corresponding to the α′-martensite consisted with the dissolution rate of α′-martensite.
It is suggested that the preferential dissolution of α′-martensite may be attributed to the high density of dislocations.

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The effect of a difference in surface conditions of emery polish and vacuum anneal on the probability distribution of stress corrosion cracking failure times of Type 304 stainless steel in boiling MgCl₂ solution has been studied. The probability distribution for crack initiation times T_i, crack propagation times T_p and also total failure times T_f is found to obey a three parameter Weibull distribution. The shape parameter estimated by the previously reported method is approximately 1.5 for T_f and T_i and 2 for T_p. It is demonstrated that peak potential, at which crack initiation occurs, determines mean failure time of μ_f, μ_i and μ_p. Surface polish causes peak potential to less noble along with the μ vs. peak potential curves and accelarates crack initiation and hence shortens total failure time.

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It has been demonstrated that anodic dissolution rate of the bare surface of steels, which is produced in the process of crack propagation, is much greater than that of the steady-state surface near corrosion potential in NaCl aqueous solutions. In order to understand the roll of anodic dissolution on corrosion fatigue crack growth rate, both the corrosion fatigue and the bare surface polarization behavior were investigated on SCM435 steel in 3% NaCl aqueous solution. Corrosion fatigue tests were carried out under various potentials (-900--600mV) and frequencies (0.03-3Hz). Bare surface polarization curves were measured by scratching electrode method with various pH and dissolved oxygen content (DO).
The results showed that the enhanecd acceleration of growth rate was observed when the potential was -600mV and the growth rate tended to increase as the frequency decreased. The theoretical curves calculated from anodic dissolution model predicted well the acceleration of the growth rate. It appaers to have a great possibility that the anodic dissolution is the rate-controlling factor in corrosion fatigue at low ΔK levels.

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The faradaic impedance of the metals under catholic polarization in a neutral solution was discussed in order to apply the impedance technique to monitoring and determining the optimum catholic protection potential.
Assuming the partial polarization curves of anodic metal dissolution, cathodic oxygen reduction and hydrogen evolution, the impedance-potential diagrams were delineated by computer simulation. It was found that, under diffusion limited oxygen reduction, the faradaic impedance shows a maximum near the virtual mixed potential determined solely by the partial reactions of anodic metal dissolution and cathodic hydrogen evolution, where a rational protection efficiency also shows a maximum. Thus the optimum protection potential can be unequivocally determined as the potential of maximum impedance. Moreover, the rate of metal dissolution at this protection potential can be calculated from the value of the maximum impedance. It was concluded that the a. c impedance technique can be successfully utilized for determining as well as monitoring the conditions for cathodic protection.

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