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  for Metal Finishing since 1989
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Making paint stick to nickel without hex chrome?

2003

The US Military has outlawed Hex Chrome and now I have a paint adhesion problem over nickel, and I'm hoping one of the experts can point me in the right direction.

We manufacture suspension systems for military vehicles. One of our applications has the following build-up:

Base metal: 4140 Steel, hardened
Plating: Electrolytic Nickel per FED-QQN-290 (replaced by AMSQQN290)
Prepare per TT-C-490 [from DLA] ; Clean per Method III (alkaline wash), pretreat Type I (Zinc Phosphate) or Type III (Organic Pretreatment Coating per DOD-P-15328 )
Finish using MIL-P-53034 Primer (epoxy) and MIL-C-46168 Topcoat (polyurethane).
Performance Requirement: Adhesion per TT-C-490 [from DLA] , 336 hrs salt spray perASTM B117

Up until now, we were pretreating per TT-C-490 [from DLA] Type III, using DOD-P-15328 Organic Pretreatment Primer. The most recent contract we received indicates that hex chrome is no longer acceptable, meaning we can no longer use vinyl wash primer as a pretreatment. We have moved to Zinc Phosphate instead, and we have had success on all our ferrous applications.

We have been at it for over a year, trying to get our paint to stick to nickel. Just when we think we have something, the confirmation test reveals a problem, typically loss of adhesion at the 250 - 300 hour mark.

The customer is being inflexible and will not budge on the requirement for nickel plating, nor will they budge on the requirement for a CARC paint finish over it (Anyone who does military work can sympathize). None of our plating subcontractors, or our chemical or paint suppliers have been able to offer a working solution, and we have tried too many potential solutions to list here and still respect your time. The only process that seems to work is a zinc-nickel plating over top of the QQ-N-290, but the cost of the additional plating step is prohibitive.

Can anyone tell me if there is some way we can modify the nickel plating so that it still complies with QQ-N-290 but will offer us a surface that paint will stick to? Any help on this is greatly appreciated.

Thank you.

Chuck Williamson
- Georgetown, Ontario, Canada

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This probably will not help Chuck but I do like to solve problems - I was in a very high quality company in Aerospace for many years and we were the best: 1. Sometimes a customer would come to us with a NEAR impossible requirement and we would fix it. 2. Sometimes a customer would come to us with a QUITE impossible requirement (usually because he didn't understand our technology limits well enough) and we couldn't fix it so we told not to be unreasonable and come back later with a modified requirement. My point is Chuck that sometimes the customer IS WRONG and has to be told that he will have to pay or change his spec - even the President of the USA cannot have paint that smells like lilacs - unless perhaps he pays a lot of money.

Richard Alan Bates
property refurbishment - Waterlooville, England, UK
2004