Determination of passive film thickness of tin plate type 71 by X-ray fluorescence spectrometry
The passive film thickness of tin plate type 71 is closely related to the product quality and proper-ty,so its accurate determination is of great significance.Seven pieces of tin plate type 71 samples with dif-ferent passive film thickness gradient were selected and sampled according to the satellite sampling method in GB/T 1838.The spectrophotometry in GB/T 28290 was adopted for quantification.These samples were used as calibration sample series for the preparation of calibration curve.The determination of passive film thickness of tin plate type 71 by X-ray fluorescence spectrometry(XRF)was realized.Since the passive film type 71 contained various forms such as chromium oxide,chromium hydroxide and chromium metal,and the storage and quantification of passive film standard sample could be seriously affected by the content of chromium metal and the variation of chromium oxide layer with time,the accuracy of calibration curve would be influenced.The methods for rapid stabilization of passive layer were discussed in experiments.The corrosion resistance of surface passive film was investigated using polarization curve.The results indi-cated that when it was heated at 200 ℃ for 15 min,the corrosion current density was lowest,and the cor-rosion resistance of tin plate was best.The calibration sample 2# with passive film thickness of 4.26 g/m2 was used for short-term stability and long-term stability tests.The results showed that the relative stand-ard deviation(RSD,n=10)of determination results of short-term stability and long-term stability tests was 1.2％and 2.0％,respectively,which could meet the requirement of intra-laboratory RSD less than 5.3％in GB/T 27417.Six samples of passive film tin plate type 71 were selected and analyzed according to the experimental method and spectrophotometry in GB/T 28290.The results showed that the found re-sults of this method were basically consistent with those obtained by spectrophotometry.The statistical magnitude P=0.817 5 was obtained through calculation,indicating that there was no significant difference between two groups of data.
tin platepassive film type 71X-ray fluorescence spectrometry(XRF)thickness
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