Adhesion Test for precious metal plating
Q. Dear Reader,
I am interested in a non destructive adhesion test for electroplated stainless steel parts with a precious metal. I would be grateful for any suggestions with regard to this test as it is proving quite difficult to find any company / literature which can offer a solution.Sean O Reilly
- Republic of Ireland
A. Adhesion tests are destructive to at least the plating. the chisel test is the only test that I am aware of that is only minorly damaging to the parent metal.
Most shops will run test panels or scrap parts that are absolutely identically processed and those are destroyed.James Watts
- Navarre, Florida
A. Hey Sean,
I have used a high tach (very sticky) cellophane tape (I think is was Scotch tape #602). All you do is press the tape in place and run your finger over it to get out the air and make good contact with the surface. A quick pull of the tape should tell if you have adhesion. As I remember, the tape represents about 5 to 10 pounds per square inch. A little bit of alcohol on a soft rag (we used a lint-free paper product) will clean off the residue.
Regards,Fred Mueller, CEF
- Royersford, Pennsylvania
A. I conduct testing of plated and coated automotive parts. You might want to get a copy of ASTM B571 [link by ed. to spec at TechStreet]. This is a specification from the American Society for Testing and Materials and is titled "Standard Practice for Qualitative Adhesion Testing of Metallic Coatings." It is a few adhesion tests that may or may not be applicable to your situation. I have found that adhesion testing usually is destructive, even some of the tape tests.
I have done some adhesion testing in the past. The tests I have done consist of a corrosion test (salt spray or CASS), scribing the part (which is destructive) before or after the corrosion test, then using pressure-sensitive tape. The tape is applied then peeled away quickly to see if any coating or plating peels away with the tape.
I hope this helps!
Rochester Hills, Michigan
A. You might also try glass bead peening. It is used on IVD aluminum coatings all of the time with little damage to the substrate. If the coating comes off, the adhesion is bad. The peening also densifies the coating, important for IVD aluminum. Any IVD aluminum facility will have a glass bead capability if they do work for the military -- it's part of the MIL spec.
- Vista, California
A. The tape test is a formal test for a couple of things in metal finishing. I do not think it is appropriate for a precious metal finish. I would not want to buy a watch or a pin or a pen that I paid gold, silver, or etc. price for to only pass a tape test. I doubt if your customers will buy off on it either.James Watts
- Navarre, Florida
Have you tried a bake test? We have used bake testing to not only enhance adhesion, but to check for blisters and lifting plating. (250 Degrees C for 1.0 hour, 400 degrees C for 5-20 min. pending on the grade of your Au deposit.)
Good Luck,Mark Kruzel
- El Cajon, California
A. Dear Mr Sean,
There is this test prescribed for Silver Plating in Indian Standards :
that is to take a round tipped Mild steel rod and rub it back and forth five six times on the Silver/precious Metal plating . The Heat caused by the vigourous rubbing and pressure applied causes an improperly adhered plating to come off and fail the test.
Haven't tried it myself and I am quoting from a Sunday morning hangover memory. If you want a copy of the Indian Standards, write again with your mailing address to enable me send it to you.
Bangalore, Karnataka, India
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