This master’s degree dissertation purpose is evaluate, by means of metrological validation techniques, the reliability of the analytical method by Xray fluorescence, used in quantitative analysis of chemical species presents in various materials used in steel production process. The method study and the evaluation of the analytical equipment capacity associated with the correct understanding of the steps of receiving, preparation and analysis of samples will define the critical issues of control to guarantee the emitted results. As motivation, the interest for ensuring the implementation of a method already known in the new demands of chemical analysis, supplying the needs of customers, optimizing, thus, the services provided in the laboratory responsible for quality control of ArcelorMittal Tubarão. The methodological study development was based on good practice of metrology in order to ensure adequate measurements made during a production process, reducing consumption and waste of raw materials and generating productivity gains. In accordance with the EURACHEM Guide, the method validation took into account the Confirmation of identity, Selectivity / Specificity, Limit of detection, Limit of quantification, Recovery, Working and linear ranges, Accuracy, Trueness, Precision (repeatability, intermediate precision) and Robustness. Among the results, the study validates the method for routine work, qualifying X-ray fluorescence as a method of analysis for materials tested in the laboratory. As conclusion the study of the metrological validation methodology leaves a bibliographic source of the method and equipment used, in order to spread these principles. Another contribution of this work was the possibility of expanding this technique to other analysis realized in the laboratory of ArcelorMittal Tubarão.