The regulations that should be followed when using the coating thickness gauge
a Base metal properties
For the magnetic method, the magnetic properties and surface roughness of the base metal of the standard piece shall be similar to those of the test piece base metal.
For the eddy current method, the electrical properties of the base metal of the standard sheet shall be similar to those of the test piece base metal. the
b base metal thickness
Check whether the base metal thickness exceeds the critical thickness, if not, use one of the methods in 3.3 to calibrate. the
c edge effect
Measurements should not be made close to sudden changes in the test piece, such as edges, holes and inner corners. the
d Curvature
Measurements shall not be made on curved surfaces of test pieces. the
e Number of readings
Often several readings must be taken within each measurement area since each reading from the instrument is not identical. Local variations in cover thickness also require multiple measurements in any given area, especially when the surface is rough. the
f surface cleanliness
Before measurement, any attached substances on the surface should be removed, such as dust, grease and corrosion products, etc., but do not remove any covering substances
