Now talking about measuring a surface coating's thickness using the so called "calotest".
With a ball of steel and diamond suspension as grinder, you grind a calotte into the surface.
Looking at that calotte with a microscope, you will gain a view like the scheme above indicates: two concentrical circles.
By measuring these circles diameters you can calculate the height "h" of the surface:
The total depth of the Calotte T is:
the depth of the calotte in the substrate t is:
thus, the height h of the surface is:
as the radius R of the steel ball is much greater than the diameter of the calotte, this equation can be simplified to:
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