Galvanic corrosion between carbon steel and soldering fluxes was studied in a concentrated LiBr solution at 383 and 433K, using extreme-value statistical analysis of pit depth in soldered parts, measurement of the amount of dissolved Fe2+ and dissolved flux compornents, and corrosion potential and galvanic current measurement. The soldering fluxes used were copper, copper alloys (Cu-Si-Mn, BAg-8, Ag 30-Cu, 70/30 Cupronickle) and nickel. Nickel flux soldered with carbon steel caused considerable galvanic corrosion of carbon steel at 383K, while carbon steel soldered with copper and copper alloy fluxes showed galvanic corrosion of the fluxes at 383 and 433K. The galvanic corrosion rate of fluxes decreased in the order of copper>Cu-Si-Mn>Ag 30-Cu>BAg-8> 70/30 cupronickel at 433K, and Cu-Si-Mn>copper>Ag 30-Cu>BAg-8>70/30 cupronickel at 388K. 70/30 cupronickel flux was considered the most suitable soldering flux in a concentrated LiBr solution at high temperature.
The effects of immersion or electrolysis in nitric acid solutions on the corrosion resistance of stainless steels ground using an abrasive belt and polishing oil were studied by immersing plate specimens of SUS 430, SUS 430LX, and SUS 304 belt-ground using a sulfurized mineral oil in 5∼30mass % HNO3 for 60min or by electrolyzing them in 10mass % HNO3 for 8-16s at 50 or 60°C. Corrosion resistance of samples was evaluated by a modified ferroxyl test and salt spraying followed by drying and wetting (SDW) rusting tests. We found that immersion in 10-20mass % HNO3 was more effective than that in 30mass % HNO3 and that cathodic or alternating electrolysis was more effective than anodic electrolysis in improving corrosion resistance of samples. XPS showed that effective immersion and effective electrolysis in nitric acid solution decreased sulfur content in the surface film. Corrosion resistance is presumed improved by repassivation after dissolution of the original surface film containing sulfur in nitric acid solution.
A photoresist-patterned, rolled TiNi (50at% Ti-50at% Ni) sheet 150μm thick was etched electrochemically in 5% H2SO4/CH3OH solution and the effects of applied voltage and pattern width on etch rate and etching accuracy were studied. SEM observation and AES depth analysis revealed that the rolled TiNi specimen had an unetchable surface oxide layer about 3μm thick. The specimen was etched through microcracks in the oxide layer, then distributed throughout the alloy bulk beneath the oxide layer. At an applied voltage exceeding 6V, grooves of different widths were etched uniformly at 0.15μm/s and an etch factor of about 2, independent of groove width. Etched grooves wider than 500μm had a W-shaped profile due to the current flow concentration at the edge of the photoresist mask aperture. At an applied voltage below 5V, uniform etching did not occur at grooves wider than 500μm. We also took a brief look at the oxide removal before etching.
Nickel, copper and copper oxide films were fabricated by electroless plating and chemical oxidation. The analytical performance of glucose by constant potential amperometry was studied in the flow system with films. An electrocatalytic glucose oxidation peak appeared in cyclic voltammograms of all films, similar to films prepared by other methods. In the flow system, the largest current was observed for the copper oxide film: excellent stability and the widest calibration curve linearity were also seen for the film. Scanning electron microscopy revealed a fine network structure for the copper oxide film. The large surface area due to such structure probably resulted in the large current.
The origin of inductive behavior in electrochemical impedance during metal deposition was discussed based on numerical analysis. Impedance was calculated by the modulation of adsorption coverage Δθ/ΔE as follows: 1/Z=AF+jωCdl, AF=aA1+aA2 Δθ/ΔE, Δθ/ΔE=aθ1(jωaθ2+1), where AF is admittance, Cdl capacitance of electric double layer, ω angular frequency, and ai constant. Results of calculation indicate that the following adsorption processes are related to inductive behavior in metal deposition: (i) adsorbed intermediate in consecutive reaction, (ii) cathodic adsorbed species as catalyst, and (iii) anodic adsorbed inhibitor.
Photovoltaic performance of a Schottky barrier phthalocyanine binder layer solar cell was studied, together with NO2 adsorption influence on performance. A phthalocyanine layer was prepared on an indium tin oxide (ITO) glass substrate by spin coating, and a semitransparent aluminum electrode was vacuum-deposited on the phthalocyanine layer. Copper phthalocyanine (CuPc) was used as a photoactive particulate semiconductor, polyvinylidene fluoride (PVdF) a polymer binder and N, N-dimethylacetamide (N, N-DMA) as a solvent. The CuPc solar cell showed good rectifying characteristics in the dark and photovoltaic effects under light illumination. The photovoltaic performance of the solar cell was improved by NO2 adsorption onto the CuPc layer, attributable to increased carrier (hole) lifetime caused by the NO2 adsorption capturing electrons. However, NO2 adsorption promotes oxidation of the aluminum electrode and deteriorates the Schottky barrier between the CuPc layer and aluminum electrode, deteriorating the solar cell's photovoltaic performance.