Effects of temperature and concentration of silicate anion in water on corrosion behavior of hot-dip galvanizing were investigated by immersion test, surface analysis, and cross-sectional observation. Immersion test using ion-exchanging water indicated that the corrosion rate decreased due to deterioration of water quality. X-ray fluorescence analysis revealed that much more Si exist on surface of hot-dip galvanizing sample after immersion test using deteriorated water compared to clean water. Now we prepared corroding liquid by adjusting the concentration of silicate anion using distilled water and sodium silicate in order to confirm the effect of concentration of silicate anion on corrosion rate by immersion test. In this test, higher concentration of silicate anion led to lower corrosion rate as well as in the immersion test using ion-exchanging water. Moreover, the influence on the corrosion inhibition by silicate anion was larger in corroding liquid at 60℃ than at 25℃. Glow discharge optical emission spectrometry revealed that more Si existed in the corrosion products on surface of hot-dip galvanizing immersed in 60℃ than in 25℃ water, and the thickness of corrosion products containing Si was about 20-30 nm by cross-sectional SEM image.
Microscopic hydrogen visualization has long been required to clarify the hydrogen embrittlement mechanism of metallic materials. In this study, hydrogen diffusion depending on microstructure in polycrystalline pure nickel film was successfully visualized using an Ir complex, whose color changes with hydrogen. The hydrogen flux in nickel was found to be large at random grain boundaries and small inside grains and at coincidence site lattice grain boundaries.
Soil corrosion rate for architecture and civil engineering is regarded as 0.02 mm/year regardless of the soil. However, it is considered that corrosion rates of each soil are different because soil properties such as particle size, water content, chemical composition and pH are different. In this study, we measured dissolved oxygen diffusion coefficient of each soil and each water content and evaluated the charge transfer resistance of each dissolved oxygen concentration by AC impedance method, to investigate the effect of dissolved oxygen diffusion on soil corrosion.
It was suggested that major oxygen diffusion path in soil is air that dispersed into soil. As a result, dissolved oxygen diffusion coefficient was correlated with air-filled porosity. It is suggested that the corrosion rate in soil increase with increase of air-filled porosity (decrease of water content) in case of considering not metal-water interface surface area.