Nondestructive Measurement of Hexavalent Chromium in Chromate Conversion Coatings Using X-ray Absorption Near Edge Structure

We developed a nondestructive evaluation technique of hexavalent chromium (Cr 6+ ) in chromate conversion coatings on the basis of a pre-edge peak that appeared in an X-ray absorption near-edge structure (XANES) measured at the SPring-8 synchrotron radiation facility BL16B2. By applying this technique, a percentage of the hexavalent chromium in the actual chromate conversion coating has been evaluated. Furthermore, to determine the depth distribution of hexavalent chromium in the coating, grazing incidence X-ray fluorescence (GIXRF) measurement has been performed. From the data analysis, we found that hexavalent chromium concentration is decreased around the surface region of the coating.