The diffusible hydrogen in the metals plays an important role in the delayed failure and hydrogen embrittlement. Therefore, the focus is on detection of hydrogen permeated through the steel in this article. The detection of permeated hydrogen electrochemically（Devanathan-Stachurski double cell）is explained in detail. It also demonstrated that the application of micro-electrochemical cell to detected permeated hydrogen during wet/dry corrosion of scratch formed zinc coated steel.
This paper presents an introduction of the polarization techniques using a micro-scale electrode area. It starts with the information about a capillary-based micro-electrochemical cell and a micro-scale electrode fabricated by a coating method, followed by several characteristic features and existing problems. Finally, the paper provides some applications of micro-scale polarization to corrosion research.
The effect of precipitates on filiform corrosion （FFC） growth of coated Al-Mg-Si-Cu alloys with different coolings and chemical components was investigated using a cyclic corrosion test and dynamic polarization in an acid solution. Total FFC growth was accelerated by air cooling, while being suppressed by water quenching for high Cu contained Al alloy. Comparing water quenching with air cooling, cathodic current densities and the number of precipitates including Cu were lower after water quenching at high Cu contained Al alloy. These results suggest that suppression of precipitates including Cu improves FFC growth resistance of Al-Mg-Si-Cu alloys.
CAC 905 is a recently developed lead-free copper alloy composed of 15％Zn-2.5％Sn. In the present study, the corrosion resistance of CAC905 was evaluated and compared to the conventional lead-containing bronze CAC406 using salt water cyclic corrosion test （CCT）, salt water spray test （SST） as well as the corrosion test for determination of dezincification resistance. It was found that CAC905 has an equal corrosion resistance to CAC406. Dezincification phenomenon was not observed in CAC905. Polarization test showed that the polarization curves of CAC905 in 3 mass％ NaCl solution is similar to that of CAC406, supporting the corrosion test result that the corrosion resistance is almost the same for CAC905 and CAC406. SEM/EDS and XRD analyses conducted on CAC905 specimens after CCT for 240 hrs revealed that corrosion products of Zinc were deposited on the CAC905 alloy surface, which may depress the anodic reaction of CAC905 alloy.
The number of photovoltaic system has increased drastically due mainly to a profitable selling price of electricity for owners set by feed-in tariff. Metal piles are currently used as typical foundation of the system from the viewpoint of high workability and low cost. However, there is a problem that the corrosion rate of metal foundation pile at ground level is faster than that of other part of the pile. In this paper, soil corrosion at shallow layer was investigated by exposure test in soil, chemical analysis of soil and electrochemical analysis. The corrosion rate of metal pile in shallow soil layer was higher than 0.02 mm/year which is commonly recognized as the corrosion rate of metal in soil. The corrosion rate in shallow soil layer mostly increased with decreasing the polarization resistance measured in soil environment. Those investigated results showed that the macro cell corrosion at ground level is thought to be attributed to change of chemical composition caused by land creation and dispersion of manure.
Localized corrosion in crevice of SUS316 stainless steel after immersion in 288℃ high purity water with dissolved oxygen concentration of 32 ppm for 100 h was analyzed. Two different types of localized corrosion initiated on grain boundary and inclusions. The former initiated on grain boundary and oxide grown into grain matrix. The oxidized area showed duplex structure composed of microcrystalline FeCr2O4 and island-shaped residual metals. The latter initiated on inclusions containing Ca and S and microcrystalline FeCr2O4 grown into metal matrix. These localized corrosion occurred selectively in oxygen depleted area indicated formation of macroscopic corrosion cell with the corroded area as anode and surrounding oxygenated area as cathode.