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Delamination of powdercoating on nickel

2005

We have parts which have been nickel plated that the customer wants powdercoated. The problem is delamination is occurring especially over chamfer holes and around openings.
We pre-bake to remove any vapor outgassing. Is this a result fo dirty rinse water, parts improperly rinsed and dried using a surfactant or should it be zinc rich pretreated prior to powder application?

If none of the above what could be the delaminating cause?

Wyatt Buchanan
- Binghamton, New York

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Dear Wyatt,

Your client has asked you to powder coat one of the most difficult substrates to which to apply powder.

Try to obtain some TWO Pack Etch/Wash Primer and apply this to the nickel prior to coating and this may overcome the defect.

Make sure you have achieved FULL cure of the powder.

Zinc Rich will not overcome your problem.

Please supply progress report to enable further assistance.

Terry Hickling
Birmingham, United Kingdom
2005

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2005

A poorly prepared surface could be part of the problem, but the areas in which you describe the failures (holes, etc.) make me think that it may be undercure of the powder coat, as Terry says. Knowing the chemistry (urethane, TGIC, epoxy or other) would be a help. When coating vendors indicate a temperature range for proper cure of the powder coating, it is the temperature of the substrate that is important. Curing a heavy steel part for the specified time will not usually give you a fully cured coating. The part must come up to the full cure temperature before the cure timing is started. A 20 minute cure time means 20 minutes with the substrate at the cure temperature.

ACRONYMS: TGIC = polyester triglycidyl isocyanurate

There are many companies that powder coat over a nickel finish with success, so don't give up trying.

If you are sure that you are achieving full cure, you might try installing a deionized water rinse after your pretreatment. I should be a low pressure spray to be most effective. By the way, The Powder Coating Institute offers a number of good teat methods for testing cure.

Daryl Spindler, CEF
decorative nickel-chrome plating - Greenbrier, Tennessee