The graph shows the typical surface finish produced by an aluminum oxide abrasive: Curves illustrate the range of results from pressure and abrasive size variations. Exact results will be influenced by material differences, nozzle selection, and other variables. Surface roughness values are generally expressed in microinch (μin.) or micrometer (μm) units.
The American National Standards Institute’s standard for surface roughness measurements calls for Ra which is the arithmetic average deviation from the mean (ANSI B46.1-1978, “Surface Texture,” American Society of Mechanical Engineers).
Other definitions of roughness, such as root mean square, are falling into disuse. There are many other significant attributes of roughness that are equally important, if not more so, in defining roughness. Those parameters help to define the population density of irregularities and surface area. The graph shows a guide to surface roughness expected from alumina of various grit sizes on typical substrates.
Source: ASM Handbooks Online. Volume 5A, Thermal Spray Technology -> Thermal Spray Processes and Coatings -> Introduction to Coating Design and Processing -> Processing Prior to Coating
