7.5 Finish—Test specimens should be smooth, flat, and free of scale. Surface defects such as porosity and roughness may bias the test results, and such specimens should be avoided unless the surface itself is under investigation. Typical suitable surfaces are mill-rolled surfaces such as are present on cold- rolled steel, electroplated and similar deposits, ground surfaces, and finely machined or milled surfaces. A ground surface finish of approximately 0.8 µm (32 µin.) or less is acceptable. The type of surface or surface preparation shall be stated in the data sheet.