Laser-induced breakdown spectrometry; X-ray fluorescence spectrometry; Chromium; Surface layer; Steel sheets;DEPTH PROFILE ANALYSIS; GALVANIZED STEEL; COATED STEEL; ABLATION; SPECTROSCOPY; COPPER

A method was proposed for the determination of Cr in a thin surface nanolayer deposited on top of a micrometrical Zn-based anticorrosive coating of steel sheets using laser-induced breakdown spectrometry . Optimization of the LIBS parameters was performed with respect to the statistical parameters of regression, these being the coefficient of determination , akaike information criterion and mean-squared prediction error. These were calculated for curves describing the relationship between the Cr surface concentration and the intensity of LIBS signal. The most critical parameter of analysis appears to be the focal spot diameter. When its value was 200 mu m and corresponding energy density had value of 413.8 J/cm, the intensity-concentration relationship revealed a negative slope. This phenomenon was caused by the difference in total ablated volume for samples with a different content of Cr in the surface layer. This phenomenon was not observed for higher values of the focal spot diameter and lower values of fluence ). A range of calibration obtained under optimal conditions was 11-21 mg/m and the limit of detection was 0.7 mg/m. The recovery values calculated from the results of the proposed LIBS method and the standard ED XRF method ranged from 99.2 to 101%.