As relates to an anode and a cathode, a life test of about 2000hrs has been conducted with a single cell using an anode that has improved catalyst material. As relates to the improved cathode durability, the relationship between the types of carbon supports for the cathode catalyst and the cell characteristics was investigated. If the dibutyl phthalate (DBP) absorption value increases, the O2 gain tends to decrease. Results indicate that gas diffusion increases with use carbon supports having DBP absorption value (a highly developed carbon support structure).
During AC etching of aluminum foil used in electrodes for electrolytic capacitors, an anodic oxide film and a non-uniform aluminum hydroxide develop over the etched cell surface. The effects of these products on enlargement of surface area were investigated in 3.6wt% hydrochloric acid solution at 303K by applying AC with an asymmetrical triangular wave and a compound waveform of anodic current with a triangular wave and cathodic current with a square wave. The amount of aluminum hydroxide was measured using a stripping method and the thickness of the deposition layer was calculated assuming that the product is present homogeneously on the entire etched cells surface. Marked enhancement of specific surface area was obtained under condition where the deposition rate of the aluminum hydroxide at the half cycle of cathodic current was high and the pit nucleation potential at the half cycle of anodic current was maintained at about -0.2V (vs. SCE). Larger pits appear at a more noble potential and dissolution takes place on entire aluminum surface as a whole at a less noble potential. The breakdown behavior of anodic oxide film is affected by the cycle of cathodic current to controll the rate at which chloride ions are supplied to the etched cell surface.
The galvanic currents of Atmospheric Corrosion Monitors exposed to the atmosphere are analyzed in order to investigate the scaling behaviors of corrosion. It is found that the time series of the galvanic current have the scaling properties and a scaling relation derived from the scaling theory is consistent with the experimental results. The Hurst coefficient representing the effect of long memory is related to the type of corrosion.
Powder coatings have attracted attention as environmentally friendly coatings. Development of powder coatings with an excellent corrosion resistance and weathering resistance and determination of a method of evaluating these coatings must take place rapidly. In this research, the effects of different kinds of coating films (resins and pigments) on the corrosion resistance of powder-coated steel sheets were evaluate using an Ac impedance method after conducting accelerated weathering tests and outdoor weathering tests. By means of Cole-Cole plots, the size of the capacitive semi-circle was reduced as the coating films continued to deteriorate, and the effects of corrosion below film caused by the diffusion of dissolved oxygen were noted. The resistance of powder-coated steel sheets after accelerated weathering tests and outdoor weathering tests dropped with a long exposure time. The drop rate was lower with resin specimens for coating films with substantial weathering resistance than with resin specimens for coating films with slight weathering resistance. Furthermore, the rate was lower for specimens to which TiO2 white pigments had been added than for specimens of azo red pigment. When the moisture permeability and oxygen permeability increased, the resistance of the powder-coated steel sheets dropped. Furthermore, the coating film surface displayed progressive deterioration with a long exposure time, and the deterioration for coating films containing red pigments was more noticeable than for coating films containing white pigments. In accordance with the XPS method, the production of ketone, carboxylic acid, etc. can be expected to occur as the deterioration of the coating film surfaces progresses.
The hardness and tribological properties of multilayered Cu/Ni-P coatings prepared via electrodeposition with a single bath containing nickel sulfate, copper sulfate, phosphoric acid and sodium citrate have been examined. The location of Cu and Ni-P sublayers that were alternately deposited at 1mA/cm2 and 50mA/cm2, respectively, was analyzed. These sublayers consist of crystalline Cu and amorphous Ni-P. Results have indicated that the hardness of the multilayered coating is lower than that of Ni-P single coating and increases with an increase in the thickness of Ni-P sublayers. A remarkable finding is that wear resistance of the multilayered coating is superior to that of Ni-P single coating, which may be attributed to the suppression of the propagation of cracks in the multilayered structure.