Scratch Resistant Coatings

Improving the life of a coating such as polyurethane, acrylic or epoxy can be achieved with the addition of a small amount of a abrasive such as Aluminum Oxide, White Aluminum Oxide or Silicon Carbide. These materials are significantly harder than the coating material and will increase the scratch resistance of the coating with minimal impact on the other properties of whatever coating you are using.

The specific type of abrasive will depend on a variety of job specific requirements including color, clarity and thickness. The size of the abrasive used is generally a very fine grade such as a 600 or 800 mesh but larger grit (~240 mesh) can be used in thicker coating. The addition rate is also very dependent on the coating you are using specifically related the solids content. Rates of 3 - 5% (about 1/2 pound per gallon) are common.

Anchor Profile

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.