What is the standard test method for the determination of Mohs scratch hardness?

 

In this test, a set of pencils of different hardness levels (from 6B (softest) to 9H (hardest)) are used to scratch the surface of the coating. The hardness of the pencil that does not scratch the coating or only barely scratches it determines the Mohs scratch hardness of the material.

 

The test is performed by applying the pencil at a 45-degree angle with consistent pressure while moving it back and forth across the coated surface. The scratch hardness of the coating is determined by the pencil rating that produces the visible scratches.

 

Please note that while the Mohs Scratch Hardness Test provides a quick and easy assessment of hardness, it may not be as accurate as other methods such as the Vickers or Rockwell Hardness Test. It is primarily applicable to thin coatings and does not provide an absolute hardness value.

 

Of course, in addition to the ASTM D3363-05 (2011) standard test method, the Mohs scratch hardness test can be performed using other hardness scales, such as a durometer or pocket hardness tester. These methods involve scratching the coating with a pointed or rounded tool and assessing the depth or size of the scratch.

 

It is important to note that the Mohs scratch hardness test only evaluates a material's ability to resist surface scratches and is not an accurate measure of its overall mechanical strength or abrasion resistance. Other factors can affect the durability of a coating, including adhesion, chemical resistance and impact resistance.

 

The Mohs scratch hardness test is commonly used in the coatings industry to evaluate the scratch resistance of paints, varnishes and other coatings. It is also used in the jewelry industry to determine the scratch resistance of different gemstones. Overall, the Mohs Scratch Hardness Test is a simple and useful method of determining the scratch resistance of a material, but should be used in conjunction with other tests and evaluations to fully assess the mechanical properties of a material.