The anchor pattern or etch profile on a surface created during abrasive blasting is critical to the subsequent application of a coating such as paint. The anchor pattern is basically the peaks and valleys on the surface of the metal (or any surface) on a microscopic scale. Often coatings manufacturers will specify the profile for optimal adhesion of the coating being used.
The profile is expressed in millimeters, microns or mils. Anchor patterns generally range from 3 mils and lower and is measured by the depth of the 'valley'.
1 mil = 0.001"
39 mils = 1 millimeter
25 microns = 1 mil
The proper profile will be allow the paint to adhere but completely cover the surface.
If too much etching occurs, the 'peaks' will have a tendency to stick above the coating and lead to coating failure over time. If the profile is too small the surface between the material and coating is minimized causing improper bonding.
The media type and grit size, blasting pressure, distance from the surface, angle of blasting and surface hardness will all impact the final anchor profile.
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