Self-healing protective films were prepared on iron and zinc electrodes by treatment with environmentally acceptable corrosion inhibitors. The electrodes coated with the films were scratched with a knife-edge crosswise and immersed in an aerated 0.1 or 0.5M NaCl solution for many hours. The protective and self-healing abilities of the films were examined by polarization measurement and observation of pit formation within the scratches. X-ray photoelectron spectroscopy and electron-probe microanalysis of the surfaces scratched and immersed in the NaCl solution revealed the protective and self-healing activities of the films against corrosion of iron and zinc.
A copper cooling jacket is the major component in water cooling system for electronic equipment. Corrosion of this jacket is mainly induced by corrosive dissolved ions from other components made of organic materials. We investigated both an ion exchange system with ion exchanger and an inhibitor system using a benzotriazole (BTA) solution as methods of controlling cooling water. A life estimation method for the ion exchange system was established considering decrease in ion exchange capacity of ion exchange resin and dissolution of corrosive ions. The cooling system examined in this study should be able to replace the ion exchange resin for at least four years. A life estimation method of the inhibitor system was established considering decrease of BTA concentration and effective BTA concentration controlling copper corrosion. This cooling system should be able to provide the BTA inhibitor for at least three years. To achieve a new cooling system for controlling cooling water for ten years, we proposed an ion exchange and inhibitor multiplex system. As BTA adsorbed on ion-exchange resin dissolves gradually in the cooling water, BTA can be maintained at above an effective concentration controlling the copper corrosion for 10 years. Furthermore, by using ion exchange resin adsorbed BTA, an ion exchange and inhibitor multiplex system can be achieved without structural modification of an existing ion exchange system.
In MgCl2 solutions containing silicate ions, the susceptibility to stress corrosion cracking (SCC) for austenite stainless steel has been investigated by means of electrochemical polarization measurements, impedance measurements, slow strain rate tensile tests (SSRT), and ion transport measurements. It was found that the SCC susceptibility of austenite stainless steel was reduced by adding Mg2Si3O8 in MgCl2 solutions, and that this is due to the suppression of oxygen reduction reaction by the pH buffering effect of undissolved Mg2Si3O8. Membranes fabricated by pressing Mg2Si3O8 particles showed weak selective anion transport properties, suggesting that Mg2Si3O8 film formed during long immersion period suppresses the penetration of chloride ions to the specimen surface.
The influence of ion implantation of 22 elements on oxidation behavior of intermetallic compound TiAl has been investigated and the mechanisms were discussed. The oxidation resistance was assessed by a cyclic oxidation test at 1200K in a flow of purified oxygen under atmospheric pressure. The possible mechanisms for the improvement are as follows: (1) Formation of a protective Al2O3 scale through β-phase formed in a surface layer, in which Al diffusion is thought fast compared with γ-TiAl; Fe, Nb, Mo, Ta, W. (2) Incorporation of implanted element in TiO2 and a reduction of TiO2 growth rate due to the doping effect; P, Nb, Mo, Ta, W. The implantation of Mg, V or Cr is detrimental due to the enhanced TiO2 growth by this mechanism. (3) Protective Al2O3 layer formation through migration of volatile Al halide; F, Cl. (4) Formation of a complex oxide which promote Al2O3 formation; Zn. (5) Formation of a protective scale of implanted element; Al, Si. On the other hand, the mechanisms for the deterioration can be, (6) lattice defects induced by implantation; Ar, (7) decreased Al concentration in the implanted layer; Se, Ag, and (8) enhanced scale spallation due to a decrease in scale strength; B, N, Zr.
Deterioration of platinum in hydrogen gas environment was investigated at 340°C by means of the electric resistant measurement, and the following results were obtained; (1) The electric resistance of platinum wire increased when heated at 340°C in hydrogen for up to 1512h. Increase of 0.09Ω per 200Ω was observed after heating for 1512h. (2) According to the XRD and EBSP measurements, the increased resistance of platinum wire in hydrogen heated at 340°C was attributed to changes of lattice spacing in Pt crystals. Absorbed hydrogen in platinum resulted in the lattice spacing changes for the crystals.