Kiyokatsu Kudo

Anodic oxidation and kinetics of titanium in 1 M chloride solutions

Abstract The anodic behaviour of titanium was investigated in 1 M chloride solutions of pH ranging from 0.0 to 12.0 by using electrochemical techniques combined with chemical analysis. No active region appears in solutions of pH above 2.0. In the passive region, the amount of titanium dissolved into the solution during 1 h oxidation decreases with increasing pH, and no dissolution occurs at pH 10.5. The thickness of passive films estimated from the electric charge accumulated on the surface increases linearly with the potential. The kinetic analysis between the anodic current and the film charge indicates that the growth of the passive film obeys the inverse logarithmic rate law, and the kinetic parameters are calculated.

Intensity-following ellipsometry of passive films on iron

Abstract Structures of passive films on iron formed by a two-step passivation method in acidic and neutral phosphate solutions were investigated by means of intensity-following ellipsometry combined with a cathodic reduction technique. The passive films thus formed were generally composed of a barrier layer and a deposit layer each with different optical constants. In pH below 5.5 the barrier layer was divided into two, and below pH 2 the outer deposit layer was dissolved away. The total thickness of the film at a constant overpotential increased with the solution pH, but the thickness of the barrier layer was nearly constant irrespective of the pH.

Pressure vessel for tensile testing in high-pressure gases at elevated temperatures.

A pressure vessel for tensile testing has been developed to measure tensile stress in high-pressure up to 50.5 MPa at elevated temperatures up to 773 K. The vessel is designed to facilitate the measurement of the actual tensile load on the specimen by an external load cell without the influence of axial stress due to high pressure in the vessel and the effect of friction at sliding seals where the load rod enters the vessel. Application of the vessel to tensile testing of a steel in hydrogen atmosphere is briefly described.

Effect of hydrogen attack on tensile and creep properties of low carbon steel

Abstract The tensile and the creep properties of low carbon steel were investigated in 9·9 M Pa hydrogen and in argon at 500°C. The results obtained are as follows: 1. (1) The tensile strength and ductility in hydrogen decreased relative to those in argon with decreasing strain rate. They also decreased with increasing exposure time in hydrogen. 2. (2) In hydrogen the extent of the secondary creep stage, the creep rupture time and the creep ductility were all smaller and the secondary creep rate was greater than those in argon. 3. (3) An incubation period for hydrogen attack that is found without stress disappeared with an applied stress. That is to say, the start of hydrogen attack was accelerated by stress. 4. (4) Internal methane pressure in bubbles formed by hydrogen attack were estimated using the model given by Shewmon and the effect of stress on the bubble growth is discussed.

Apparatus for creep rupture testing in high‐pressure hydrogen at elevated temperatures

An apparatus has been developed for creep rupture testing in high‐pressure hydrogen up to 49.1 MPa at elevated temperatures up to 873 K. The apparatus is designed to facilitate the measurement of the actual load on the specimen with an external load cell irrespective of axial load caused by high pressure in the vessel or friction at sliding seals where the pull rod enters the vessel. The exact strain of the specimen can be directly measured with an external extensometer. In addition, the specimen mounting assembly is also designed to simplify the installation and operation of the apparatus. Application of the apparatus to creep rupture testing of a low alloy steel in high pressure hydrogen at elevated temperature is briefly described.