The aqueous oxidation of Alloy 600MA (mill annealed) and TT (thermally treated) materials in acidic, neutral and basic pHs (pH 4.5, 7, 10 and 14) under low and high dissolved oxygen concentrations (DO2<5ppb, ≅4ppm) has been studied using a once-through (refreshed) autoclave and Auger electron spectroscopy. The in-depth profile of composition of oxide films on Alloy 600 was measured using an argon sputtering method. Both pH and DO2 have an effect on oxide film composition and also a change in these parameters is reflected by a change in the film depth profile.
A procedure was developed to predict burn-off of a carbon-fibre reinforced composite material based on observation of weight change during isothermal oxidation at various temperatures in air and in oxygen/nitrogen gas mixtures of various partial pressures of oxygen. The oxidation process was composed of four stages, of which the second and the third were significant in practice. The rates of oxidation (Vr) at every oxidation temperature were approximated in terms of the extent of burn-off (x) by log Vr=loga+b·x for both the second and the third stages of the oxidation in air, while they were by log Vr=logV0 for the second and by log Vr=logα+β·logx for the third stages of oxidation in the gas mixture at every partial pressure of oxygen. Here a, b, α, β and V0 are constants and vary with the oxidation temperature and the partial pressure of oxygen. The variation of the values of the constants with the oxidation temperature etc. were established based on the experimental data. Burn-offs in certain oxidation conditions were calculated by numerical integration of the obtained equations. The calculated burn-offs agreed well with the observed ones.
Marine structure models were constructed at Fukuyama Bay in 1974 to study corrosion protection systems over a long term. The models consisted of full scale pipes which were protected by various heavy-duty coatings such as paints, linings, concrete and noble metal wrappings. Field investigations of paint adhesion, electric resistivity and cathodic protection system, as well as degradation in appearance, had been conducted twice a year, . This paper evaluated corrosion protection methods for marine structures based on the results of 12 years exposure. The results indicate that excellent systems for splash and tidal zones were polyethylene, rubber, epoxy mastic and metal wrappings. Also the cathodic protection of uncoated submerged steel pipes in noble metal wrapping at splash and tidal zones were achieved within the required current density of approximately 100mA/m2. From the field tests the corrosion resistance of organic coating was found to depend on film thickness. The laboratory tests showed that the minimum rupture energy of a sprayed urethane coating was proportional to the square of coating thickness.
In the production processes of lead glass, the corrosion of furnace materials causes serious problems, because lead and lead oxides melt at relatively low temperature. Anomalous corrosion occurs when ferrous metals such as seel and stainless steel are in contact with lead oxides at high temperature. This phenomenon was analysed gravimetrically. The oxidation rate of the iron coated with lead oxide powder has been measured. The oxidation rate at the temperature above 1023K was proportional to the thickness of powder lead oxide layer. In contrast, the oxidation rate reaches a maximum at certain thickness below 1023K. This corrosion behavior was explained by the formation of eutectic mixture composed of a few oxides of iron and lead.
The high-temperature protectiveness of Si3N4 films formed on Ni coupons by IBED process has been evaluated by oxidation tests between 1000 and 1400K in purified oxygen for up to 720ks. The oxidation kinetics follows a linear rate law during the initial periods and it then approaches a parabolic rate law. The main oxide identified was NiO. The nitride film crystallizes during the heating or initial periods of oxidation resulting in introduction of mechanical defects in the film. As a result of this, the protectiveness decreases with an increase in the temperature. The annealing of the Ni substrate has no significant influence on the protectiveness. A very thin film rich in Si remains on the outer surface of the NiO scale after 100ks oxidation at 1200 and 1300K.
Semiconductor under illumination produces free electrons and positive holes. These photoproduced charge carriers usually have strong reductive or oxidative forces, and sometimes decompose the semiconductor itself by these forces. This kind of decomposition is easy to take place if the semiconductor has contact with water, that is photocorrosion of semiconductor. This article explains this phenomenon using the concept of the corrosion state, and shows how to prevent the corrosion of semiconductors.
Cultural resource degradation caused by air pollution is a serious problem in the world. In Japan, this problem is also serious. Some studies of cultural resource degradation relating to air pollution have been undertaken for two decades. Studies on the cultural resource have been undertaken much more than before. Metals and alloys used for monuments, such as copper, bronze are affected by air pollution and acid precipitation. It is wellknown that bronze statue “Thinking Man” by Rodin at the Ueno Museum has been corroded by air pollution and acid precipitation. The Statue of Liberty in New York was corroded severely by acid precipitation. Some studies for metal degradation reveal the relationship between damage and affective environmental facters, such as SO2 and SO42-.