The photoelectrochemical behavior of 304 stainless steel coated with TiO2 by sputtering was studied in NaCl solutions at ambient temperature. It was confirmed that the coating from 30 to 100nm thick could protect 304 stainless steel cathodically under illumination. The coating defects don't hinder the protection performance when its area ratio is less than 1/10. As shown by Honda and Fujishima, the anodic reaction on TiO2 is neither dissolution nor photodecomposition but oxygen evolution. Therefore, the TiO2 coating is expected to work as a non-sacrificed anode. This is a highly contrasted feature of the coating as compared with zinc coating for steels which is destined to be consumed.
Characteristics of pit initiation of SUS 304L and SUS 316L stainless steels were studied using iodine solutions in which triiodide ions (I3-) accumulate with time due to the dissolution of metal between 333 and 363K. The pit initiation process of SUS 304L and SUS 316L stainless steels followed exponential laws. It was found that a stable pit growth in the triiodide solution occurred when the pit depth reached 0.1mm regardless of temperature, the initial triiodide concentration and materials. Stable pit growth had a tendency increasing linearly for SUS 304L and exponentially for SUS 316L with time.
A MOS (Metal-Oxide-Semiconductor) capacitor dissolved oxygen sensor, which has a thin porous Pt layer as a metal layer, was developed and its response characteristics to dissolved oxygen (DO) were examined in aqueous solutions containing 2.5×10-2-37 mass ppm DO at temperatures of 303-363K. It was found that the porous Pt-MOS capacitor DO sensor showed a linear relationship between the response voltage and log [DO concentration] in the range of 2.5×10-2-37 mass ppm DO at 303-363K. The responce voltage at a given DO concentration became large with decreasing thickness of Pt layer and also with increasing temperature. The response time of the sensor became short with increasing temperature. The 90% response time at a given DO concentration was less than 400s at 363 K. The slope of the linear relationship between the response voltage and the log [DO concentration] was 133mV/decade for the Pt layer 12nm thickness at 363K. The slope did not depend on the solution pH. The principle of this DO sensor was thought to be based on its Pt-EOS (Electrolyte-Oxide-Semiconductor) structure.
Electrochemical behaviour of Ag coupled with Indium-Tin-Oxide (ITO) containing 10wt% SnO2 was studied in NaCl solutions at ambient temperature. ITO accelerates corrosion of Ag under illumination in 3 and 25% NaCl solutions. Corrosion potential for Ag becomes relatively more noble in 0.3% NaCl solution than photopotential for ITO film with decreasing resistivity. Then ITO could become anodic to protect Ag from corrosion. More stable corrosion protection for Ag even in more concentrated NaCl solutions was confirmed to be obtained by additional coating of TiO2 on the ITO film.
Effect of phenol resin addition on corrosion resistance of aluminum sheet coated with epoxy resin using electrodeposition process has been investigated. Corrosion test results revealed that the weight loss of the aluminum sheet in 1wt% NaCl solution (311K, pH3.0) decreased with an increase of phenol resin addition to epoxy resin. It was found that glass transition temperature (Tg) and effective network density (ν) of the electrodeposition film were independent of phenol resin addition, but that water absorption and water permeability decreased with an increase of phenol resin addition. Water permeability was correlated well with the corrosion resistance. Corrosion behavior of epoxy resin coated aluminum is discussed in terms of physical properties of electrodeposition film against water in the coating film.
In general, a volatile corrosion inhibitor is the liquid or the solid reagent as the compound or the several mixture which is vaporized (sublimated) slowly at the normal temperature. The resulting vaporized gas has the corrosion inhibiting reaction by the chemical or physical adsorption on metal surface. In Japan, the material with this volatile corrosion inhibitor which is coated on the material, or impregnated into, or extruded into paper or film, is referred to as the “volatile corrosion inhibiting paper” or the “volatile corrosion inhibiting film” respectively, and in which this one is dissolved referred to as the “volatile corrosion inhibiting oil”. We give a general name to above inhibitors referred to as the “volatile corrosion inhibiting material”. This report comments on the summary of kind, standard, nature, property, use and application method and the future trend of these materials.