Oxidation behaviors of zirconium have been studied in nitric oxide at the pressure ranging from 10 to 50 Torr at the elevated temperatures from 610 to 800°C. This work was done in the series of investigation on the corrosion of various metals in NO gas at high temperature. The oxidation behaviors of Zr have been examined also in oxygen at the same pressures and temperatures for comparison. Various methods, such as microgravimetry, X-ray diffracrometry, massspectrometry and X-ray photoelectron spectroscopy, were adopted for this investigation. The results obtained are summarized as follows: (1) The oxidation of Zr both in NO and O₂ obeyed the cubic rate law during the early stage of oxidation. (2) The oxidation of Zr in NO was slower than that in O₂. (3) The apparent activation energies of the oxidation of Zr in NO and O₂ were 115 and 120kJ mol^-1, respectively. (4) The pressure dependence of the cubic rate constant k_c (reaction order) in the oxidation of Zr in NO and O₂ was 0.1 and -0.5, respectively. (5) The oxide layer was mainly composed of ZrO₂ in both cases, although a small amount of nitrogen probably as ZrN_x, (x<1), was also detected in the oxide layer formed in NO. (6) Only N₂ was detected as a reaction product in the gas phase for the oxidation in NO.

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The final purpose of this study is to obtain a design equation representing the estimated amount of damage which is caused to a metallic material under the simultaneous attack of cavitation and corrosive environments. To detect the influences of cavitation on corrosion process of the test specimen, the following experimental technique was adopted: the test specimen was removed from testing bath in the midst of corrosion test to be exposed to cavitation for a certain duration and then it was put back into the bath again to carry the corrosion test on. The exposure caused a sudden increase in corrosion rate of the specimen and it was found that the corroding surface is imposed with strains by the impulsive pressure of cavitation or renewed successively through removing the protective film on the surface, and thus the initial corrosion rate is always maintained. Basing upon the experimental results, an equation is proposed to estimate the amount of damage due to the corrosion component under the erosion-corrosion condition.

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The author newly proposed the application of state space trajectory method to the electrochemical analysis of corroding systems. The theory treating the potential transients of corroding systems to several current stimuli was developed. Theoretical analysis showed that the state space trajectories and their extrapolations derived the polarization resistance, solution resistance, and double layer capacitance separately with very short time polarizations. Hence, a few problems inherent in the steady polarization method could be excluded. The conceptional design of the measuring equipment for data analysis were also proposed.

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Wrought nickel base HASTELLOY Alloys, have exceptional corrosion resistance to a wide variety of chemical process environments.
This report is intended to introduce the characteristics and applications of recently improved new HASTELLOY Alloys, B-2, C-276, C-4 and G-3.

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