In situ Measurement of Dissolved Ion Concentration inside an Artificial Crevice by X-ray Fluorescence Micro-probe Technique

In this study, solution chemistries inside artificial crevices of high purity nickel and Type 316 stainless steel were investigated by in situ energy dispersion X-ray fluorescence microanalysis technique. Concentration of dissolved metal ions inside the artificial crevice was successfully measured by the technique. In case of high purity nickel, diffusion coefficient of nickel ions inside the artificial crevice was estimated as approximately 6×10-6cm2/s.Super-saturation of nickel ion at steel/solution interface inside the artificial crevice prior to formation of salt films on the metal surface was detected.The concentration was about 1.4 times higher than the saturated value. In case of Type316 stainless steel, concentration of iron, chromium and nickel ions inside the artificial crevice were decreased similarly when the potential was stepped down to open circuit potential from 0.6 V (vs. SCE). The diffusion coefficient of these ions was estimated as 8.4×10-6cm2/s. This technique is very useful for analyzing local solution chemistries.