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  for Metal Finishing since 1989
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EN adhesion problems

2002

Dear Sir,

Would appreciate if you can assist in this persistent problem. We provide EN plating to some computer parts and after bending of the part peeling occurs.

My query is

1) When we conduct a bend test for adhesion of EN plating and peeling occurs, do we consider the result as poor adhesion if the peeling occurs at the emboss point which is around the bend area?

2) If we are doing the test wrongly, which area should we do it at? The whole pc (emboss point, channel) after bending or before (flat pc/area)?

3) Any preventive measures or our process is wrong?

I hope that you can help us coz we have been having this recurring problem. Hope that you can assist us soonest possible. Thank you very much.

Jenny Koh
GS Chemistry International Pte LTd - Singapore

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2002

Jenny,

What is your substrate and what are your process before you EN plate? UnderASTM B571 (Standard practice for adhesion test for metallic coatings), it says you have to bend your part over a mandrel until the two legs are parallel. The mandrel should be 4 times the thickness of the part. Then examine the deformed area under low magnification,say 4 X for peeling. It would totally be a different test if you bend your part like folding the page of a book or you examine your part under X 10 magnification. What is the intended use of your part after you EN plate? The same way you are bending it?

SK Cheah
New Crown Hong Kong - Hong Kong

There is about a 95% probability that the problem is in the preplate process. Metal--Leaded? Then you need a fluoboride activation step added. Improper cleaning? water break test/check. Over etch or under etch? do some lab testing. How well is the part rinsed between steps? not well enough in most shops. EN parameters- You could be plating at too fast a rate. As you see, there is no simple answer.

James Watts
- Navarre, Florida
2002