The anodic behaviour of copper has been studied in alkaline solution using a rotating disk electrode and an ellipsometer. Anodic peak currents corresponding to Cu₂O and Cu(OH)₂-CUO formation during potential sweep were measured at various rotating speeds of Cu electrode. The peak current values showed a linear relationship to square-root of the rotating speed, indicating that the formation of Cu₂O and Cu(OH)₂-CuO films is controlled by the diffusion process of some species in the solution. A conventional method to prepare the copper substrate was proposed, and the refractive index of copper substrate was estimated to be 1.11-2.42i, which is in good agreement with that reported by other investigators. The refractive index of Cu₂O film, formed anodically, was 1.90-0.30i. This film appears to have a loose structure compared with crystalline cuprous oxide. The surface of copper substrate was roughened by anodic oxidation-cathodic reduction treatments.

View full abstract

The behavior of CaCO₃ precipitation from solutions containing Ca²⁺ and HCO₃^- ions was examined using vessels with and without heat transfer surface. It was found for solutions at 25°C that the precipitation takes place whenever the ion product, K_sp=(Ca²⁺)(CO₃^2-), exceeds 2×10^-7. The situation does not change with stagnant and circulating solutions. These results were inconsistent with the expectation from the Langelier index because K_sp value of 10^-9-10^-8 is assumed in calculation of the latter. The amount of precipitates was found to increase with the rise of pH and temperature. This is expected because the fraction of CO₃^2- increases with pH and the value of K_sp decreases with temperature. The behavior of scale formation on the heat transfer surface was shown to be explained on the same basis as described above. Deposition of CaCO₃ is facilitated because the temperature of the surface is considerably higher than that of the bulk solution. It was indicated that the addition of mineral acid to the solution to keep the solution pH 6.5-7.0 is quite effective to avoid the scale formation.

View full abstract

The deposition of suspended hematite particles on zircaloy surface heated with alternating current was studied in boiling at atmospheric pressure. The effects of various factors (heat flux, pH, ionic concentration, etc.) on the adhesion of particles to the heat transfer surface in the early stages of deposition were explored. The behavior of particles and bubbles formed on the heat transfer surface was observed by microscopy. The results are summarized as follows: (1) Hematite particles, having lyophobic property, are trapped on the water-bubble interface and adhere preferentially to heat transfer surface as the orbicular deposit. (2) The deposition is influenced by pH and ionic concentration related to colloidal properties of particles. (3) The amount of deposit is proportional to heat flux in the early stages.

View full abstract

Corrosion of reinforced concrete structures is grasped as the cause of deterioration phenomena by which the reinforced concrete structures lose durability and is described by dividing it into the subjects of corrosion of reinforcing steel and corrosion (deterioration) of concrete. The features of these corrosion phenomena are that numerous factors are involved, in building planning, in materials used, in concrete mix design, in concrete placement, and in the environment in which a structure is to be put, and that complex traits are thus presented. Therefore, in order to comprehend the outlines of these corrosion problems, the factors for causing corrosion are sorted out and set forth, while further, the principal items among the corrosion problems actually faced by reinforced concrete structures are discussed. Neutralization of concrete, utilization of marine aggregates, offshore structures and cracking of concrete are discussed as corrosion problems of reinforcing steel, while freezing and thawing action, sulfates, various corrosive substances, alkaliaggregate reaction, cavitation and scaling are contemplated with regard to corrosion (deterioration) of concrete.

View full abstract