Information for engineers:
Anodising is an electrolytic conversion coating, it transforms aluminium on the surface of components into aluminium oxide. Since aluminium converts rather than deposits, some of the thickness of the coating is ingress into the material and some of the thickness is growth out of the material.
A good rule of thumb is that 50% of the anodic film is below the original surface and 50% is above. So a part that is anodised with a coating thickness of 10µm per surface would only have about 5µm of growth per surface.
Standards such as ISO 7599 make use of AA designations to specify coating thickness: AA5, AA10, AA15, AA20, AA25. Based on these it establishes minimum thicknesses. Most customers find it easier to simply specify a thickness range.
from the AFC Technical Team
A 50 micron film will use up 25 microns of aluminium in its formation, thus it will create growth of only 25 microns per face.
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