Adhesion Problems over Aluminum "Silver" Leaf

      Advice on how to make a clear finish stick to aluminum leafing. October 15, 2009

Question
I am a spray tech for a small furniture company. We have been using gold and silver leaf on some of our metal products for years now with no problem. I spray ML Campbell's Klearplast over top of it. Recently we got an order for a wood piece to be silver leafed and when I sprayed it, the Klearplast peeled right off.

We did numerous samples with different methods and everywhere there is leafing it is peeling right off very easily, but literally one inch away where the only difference is no leafing, it adhered perfectly fine. We tried using steel wool on the leaf and wiping it down with alcohol before spraying and saw no improvement. There is no doubt in my mind that this is a leafing issue. We have no troubles otherwise.

I'm wondering if any of you have ever used silver or gold leaf on wood before. If so, what did you seal it with? This is a coffee table top, so it needs to be pretty durable. I think we will give a call to the company who makes the leaf and ask what their recommendation is.

Forum Responses
(Finishing Forum)
From contributor G:
Is it real silver or imitation silver leaf (aluminum)? There have been reports of difficulty finishing aluminum. Let us know what the manufacturer's recommendation is.



From contributor R:
I like Chemcraft's 2K isolante myself.


From contributor J:
If you can get a hold of the manufacturer or at least someone knowledgeable, ask them if there is any substance applied to the leaf to inhibit or prevent oxidation. Many imitation leafs contain brass and in the case of finishing pure brass, the oxidation is so quick that special lacquers may be needed that contain some phosphoric acid to neutralize the oxidation.


From contributor C:
Contributor J is on the right track. Really all you have to do is get SW's metal etching lacquer thinner and then you can use any good acrylic finish over it - the thinner contains phosphoric acid.


From the original questioner:
This is not real leaf. This is aluminum. I'm having trouble finding the company that makes the leaf since we get it through someone else in an unmarked box. It's definitely aluminum, though.


From contributor G:
Try checking at the automotive paint store. Ask what they carry to clear coat aluminum wheels.


From the original questioner:
I will do that. I got hold of the manufacturer and they recommended polyurethane...


From contributor R:
I coat aluminum inlay on tables all the time with the isolante. Excellent adhesion. Using a phosphoric acid etch is always a good practice.


From Paul Snyder, forum technical advisor:
Klearplast works well on brass and copper, but I haven't tried it on aluminum. I have used SEM etching primer followed by Magnamax on aluminum and it was very easy to peel off with a fingernail. The lacquer bonded to the primer and lifted it from the surface of the aluminum. I haven't tried it again, but it would probably be okay with a better primer.

I use 2K PU on aluminum on a regular basis with very good results. When I'm doing a clear coat on the bare metal, I start with Matthews Spray Bond and follow with the poly clearcoat. Matthews has a satin PU that does a nice job... Most PUs are gloss.

I haven't tried the spray bond/PU combination on wood... just bare aluminum. I would do a test on a wood sample that had an area gilded with the product you're using before committing to the coffee table.



From the original questioner:
Thanks for all the input. It seems 2k PU is the way to go, and since I have some of ML Campbell's Euro Series here already, I'm trying that first. If not I guess I'll move on to a sealer made specifically for surfaces that are hard to adhere to (like the Matthews).


From the original questioner:
I'm awaiting the arrival of the Matthews paint now. But I was wondering if anyone knows of a silver-colored leaf that is not aluminum that is also not insanely expensive? I saw genuine silver, and palladium, which are both out of our price range for this project.


From contributor G:
Stainless steel? Nickel?


From contributor S:
There is no leaf out there that is cheaper than aluminum, as far as I know. But the myriad of paint products available now are so good that they are a fairly convincing substitute. They don't tarnish like the early metal based bronzing powder paint. The mica based powders are so finely milled they lay out without a particle look to them. You can even make your own by putting the powders in whatever you are using for your coating. Not sure that the cost would be drastically lower than the cost of aluminum leaf, but the labor cost and dry times should improve. Might be worth your time investigating if you do a lot of this.


From the original questioner:
Thanks for the input. I'm thinking maybe in the future we should use some sort of leaf other than aluminum. Has anyone heard of any problems sealing real silver, palladium, nickel, or stainless steel? It seems aluminum is the problem, but I don't want to switch if I'm going to end up with the same problems and a higher bill for supplies.

I don't think we'll be able to spray the silver color. It sounds like something I'd like to do, but then you don't have the square patterns that leafing creates and the clients actually like to see the individual leaves.



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