Thickness of Metal Coatings

Abstract

The concept of coating thickness is clear, but surface roughness can confuse the meaning of the term. Thickness is usually not of interest in itself, but it tells us something about the properties of the coating that are really of interest such as the corrosion life or wear resistance. Instead of measuring the property of primary interest, thickness is measured because it can be measured more easily, less expensively, and nondestructively. The commonly used coating thickness instruments do not measure thickness directly but really measure something else (X-ray emmission, for example) that is proportional to the thickness of the coating. Some of the instrument measurements are not proportional to thickness unless variations of the density of the coating material are corrected for.