In a production environment, films are typically evaluated for visual defects, thickness, and adhesion. Visual defects such as bare spots, small voids, incorporated flakes, or debris can be observed with a stereo microscope having a magnification of 10 to 100 times. Film thickness is generally measured by one of the following methods: 

· Polished metallurgical micro sections are used to microscopically observe the coating thickness on various part surfaces. This method is the most direct way to determine thickness uniformity. 

· Beta (high-energy electron) backscatter instruments are used to measure the film thickness nondestructively. This is an indirect method that requires calibration with a known standard; substantial errors can be made in measuring the film thickness on curved surfaces if care is not exercised.

· A ball-crater instrument can be used to polish through the surface of a coating.

The relationship between the diameter of the polishing ball, the maximum diameter that shows the effects of polishing, and the diameter of the substrate area that is exposed by polishing is used to calculate the thickness. Coatings that are up to 120 m-in. (3Mm) thick can be measured with an accuracy of±4 m-in. (±0.1 Mm) without difficulty on relatively smooth, flat or cylindrical surfaces. The adhesion between coating and substrate is difficult to measure directly for highly adherent films; pull tests capable of measuring yield strengths that are typical of metals and PVD hard coatings on metals have not been developed. A commonly used indirect test is the manual stone abrasion test (SAT). In this test, a fine sharpening stone is rubbed back and forth across the coated surface, allowing the stone particles to make grooves in the surface by nonrealistic deformation. The film is then inspected under a microscope to obtain adhesion information.