Estimating the Uncertainty of the Result for Tests of Resistance to Environmental Conditions on the Example of the Method of Resistance to Neutral Salt Mist According to EN ISO 9227 / ASTM B117

Environmental laboratory tests are one of the most frequently performed tests to evaluate materials used, among others, for the construction of rail vehicles. The requirements of the EN ISO/IEC 17025 standard for research laboratories, particularly when evaluating the compliance of materials with the specified requirements, impose on laboratories the need to consider the results of final measurements along with the uncertainties of these results. Due to the complexity of the physical and chemical processes occurring during environmental tests, determining the sources of uncertainty of the measurement result can be very complicated. The article presents one of the methods of estimating the complex uncertainty for environmental tests on the example of corrosion tests using the NORDTEST TR 537 concept of uncertainty estimation. The article presents an exemplary method of uncertainty estimation based on a set of empirical data obtained in an accredited Laboratory for Testing Materials and Structural Elements of the Railway Institute with the use of within-laboratory reproducibility and method bias. Examples of uncertainty estimation depending on the type of tested objects (metal details and paint coatings) and the method of their evaluation after corrosion tests (quantitative and qualitative methods) are presented. The article also briefl y presents the possibilities of interpreting and processing the obtained data as part of the control carried out inside the laboratory on the basis of a simple statistical tool such as Shewhart control charts and the Ishikawa diagram for the method of determining corrosivity in salt chambers, identifying important factors influencing the measurement uncertainty and at the same time showing the complexity the entire research process.