Coating hardness

[jimmy]

Hi Everyone,

I was wondering if the members of this board could give me some advice about testing the hardness of a protective coating. I understand the basics of a durometer, but would ideally like to find a simple solution that is non destructive. The range of hardness that we get using a durometer is between 10 and 100 newtons, but most typically around 30 newtons. It is basically a combination of a layers of paint that we are trying to test. Any advice is greatly appreciated.

Thanks,

Jimmy.

[Gordon]

Hi Jimmy

to the Surface Engineering Forum.

Not much experience with testing paint films, but I know most hardness test methods use indentation or scratching, that is they will damage the paint coating. Not sure about pendulum hardness test method and Vickers or Knoop microhardness testing may minimise damage, but I doubt these methods will be suitable for you anyway.

The only thing I can think of, is the pencil test. OK the harder grade pencils will damage paint coatings, but you could use softer grade pencils as a "go or no go gauge". Select a pencil grade that does not damage the paint surface and represents the minimum acceptable hardness of your paint. When testing, paint that is not damaged will be above the minimum hardness and acceptable, paint that is damage will be rejected as being too soft. This is fine as long as you do not need to evaluate the maximum hardness or need numerical hardness values.

A few links:

(link dead) pencil hardness test

pendulum hardness test

(link dead)

Hope that helps

[hvofhamid]

hi jimmy
if you test hardness on a part of matal you don t use with same caracteristique of your pieces,may be you ll be fixed
good luck