As the corrosion-products which are formed in a halogen gas at high temperature are often volatile, it is necessary to know both the rate constants of scale-formation and scale-evaporation. The graphical method to estimate the rate constants is presented under the assumption of diffusion-controlled scale-thickening and time-independent vaporization loss of a volatile scale. The method presented is based on the derivation of the differential equation for the weight-change of the tested specimen and the numerical solution of the normalized differential equation. The procedures to estimate the rate constants are as follows; (1) Calculate the ratio of the molecular (atomic) weight of the metal tested and the corrosion-product. (2) Refer to the figures presented and determine the characteristic values for the calculated latio. (3) Calculate using these values and the data obtained experimentally. (4) Confirm the fit of the numerical solution of the difierential equation using the parameters calculated above to the experimental weight-change curve. From the rate constants, the metal recession can be estimated. A numerical example of the application of this method to the corrosion of nickel in chlorine gas is presented.

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The polarization resistance method was used to evaluate the corrosion resistance of anodized aluminum in neutral phosphate solution and the results were compared with those of salt spray and atmospheric exposure tests. It was found that the polarization resistance values at 20h immersion had a linear relationship with the pit numbers observed on sample surface. The polarization resistance, therefore, corresponds to the density of the weak points residing within oxide films. The samples anodized in sulfuric acid were definitely more resistant to corrosion than those anodized in phosphoric acid solution. The corrosion resistance of anodized aluminum was seemingly independent of oxide film thickness.

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The effects of pH and applied potential on the IGSCC of sensitized Type 304 SS were studied in dilute Na₂SO₄ solution at 285°C in connection with the polarization behaviors, in order to clarify the roles of crevice and dissolved oxygen in the evaluation of SCC susceptibility with double U-bend specimen in high temperature water. The results are summarized as follows. (1) The role of dissolved oxygen in the IGSCC behavior of sensitized Type 304 SS, is to make the potential of the steel noble. On the other hand, in the deaerated solution this same role was proved to be played by externally-applied potential, which is as noble as in the aerated solution. (2) The IGSCC in the inner specimen of double U-bend is caused by the environmental change inside the crevice, where the pH value is lowered to less than 3 due to the hydrolysis of metallic ions dissolved from the specimen, and by the potential shift of inner specimen to the transition region from an active to a passive state on the locar cell anodic polarization curve, where IGSCC can readily be generated.

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The SSRT method, electrochemically controlled SSRT method and measurement of anodic polarization curve are conducted in high temperature water for a carbon steel (STS 42) and a low alloy steel (SFVV 2) to study the environmental effects on SCC (disolved oxygen, temperature and potential). The following results are obtained. (1) The carbon steel and the low alloy steel show SCC susceptibility in oxygenated high temperature pure water, while they do not show the SCC susceptibility in deaerated pure water. (2) The low alloy steel is more susceptible to SCC than the carbon steel. (3) SCC occurs only in the high temperature water (over 200°C). (4) From the results of electrochemically controlled SSRT method in 0.1M Na₂SO₄ solution at 250°C, SCC occurs only in the potential region of higher than -400mV (vs SHE). (5) The anodic ploarization curves of the carbon steel in the Na₂SO₄ solution indicate that the steel passivates at 250°C but does not passivate at 150°C. The passivation is divided into two regions at 250°C, that is, the first passivation below -400mV and the second passivation above -400mV (vs. SHE). Judging from the Potential -pH diagram of Fe-H₂O, the second passivation is attributed to the formation of Fe₂O₃.

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The diffusion coefficient of hydrogen in 403 stainless steel was measured using a modified electrochemical technique. And the experimental results show that the diffusion coefficient should be obtained from the transient curve of permeation with 1.5-1.2 in cathodic current ratio and also the thin nickel layer should be deposited on the extraction surface of specimen.

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Seven testing methods for corrosion in dynamic environments were taken up from the experience of the author own and devided into three types of classifications namely, (1) erosin and corrosion, (2) so-called erosion-corrosion, and (3) corrosion in flowing media. Procedures to improve the reproducibility of the test results in each testing method were also described.

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