Coating thickness tester

Ball Crater

A quick method of measuring thin film coating thickness
The coating thickness tester is either referred to as a Calo® tester or ball crater equipment depending on the manufacturer. These coating thickness testers are a quick and inexpensive method of measuring thin film coating thickness.

Coating thickness tester – Basics
A rotating hardened steel sphere with a measured diameter (Ø ball) is pressed onto the surface of a coated test piece or an actual coated component. Diamond paste is applied to the sphere and as it rotates the crater is abraded through the coating to the substrate. See an impression of a coating thickness test below.

Coating thickness measurement using a Calo® tester or ball crater thickness tester
The distances “x” and “y” above are measured using an optical microscope. The thickness of the coating “t” is calculated using a simple equation shown above. Usually simple analysis software is provided with the Calo® tester / ball crater thickness tester that automatically calculates the coating thickness and allows the user to capture and store images of the ball crater for future reference. This is particularly useful when the coating equipment is part of a production department.


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