Proper sample preparation in coating testing is essential to ensure reliable, repeatable results that are compliant with regulatory standards (such as ISO or ASTM). In the case of coatings, sample preparation is also influenced by specific characteristics related to the surface nature of the substrate material. The performance of a coating—such as adhesion, corrosion resistance, hardness, and uniformity—depends heavily on either the quality of the substrate surface or the method of application. Inadequate preparation, such as insufficient cleaning, uncontrolled roughness, or surface contamination, can compromise coating adhesion and compromise test results. Furthermore, during preparation for analysis (e.g., cross-sections or adhesion tests), it is essential to avoid alterations to the coating layer, such as delamination or deformation. The thickness and uniformity of the coating must also be representative of the actual process: errors at this stage can lead to incorrect performance evaluations. Careful preparation therefore allows the true properties of the coating to be isolated, preventing external factors or artifacts from influencing the test results.