Q. Powder chips off of some of our fastener products in the field. Could you recommend a quality control test to better predict when this will happen so we can catch the parts before they make it to our customers? A.R.
A. The metal you are coating may make a difference in the test you use. If it is steel, I would try to create an impact test that applies a measured amount of impact on a chosen surface. There is an ASTM test that does this on steel panels, but it does not work for fasteners. You would need to hold the fastener firmly and drop a precise weight onto the surface. This could also work on non-ferrous metal, but you may be able to test that with boiling water. Make a small cur in the coating, and then put the fasteners into boiling water for 5 to 20 minutes and see if the adhesion breaks. The length of time depends on what kind of surface treatment you use. If it is minimal, you will only get around 5 to 10 minutes. If it is very good, you will pass beyond 20 minutes.