Epoxy on Aluminum

If you are asking if it will have the same adhesion as unreduced then no it will be somewhat less. Before you apply it it is very important that the AL is prepped correctly. You should either sand with 180 or use a product like Alodine to properly prep and remove the oxidation that forms on AL. After prep you need to get the epoxy on within 12 hours due to the fact that the AL will start oxidizing immediately after prep.
 
Chris_Hamilton said:
If you are asking if it will have the same adhesion as unreduced then no it will be somewhat less. Before you apply it it is very important that the AL is prepped correctly. You should either sand with 180 or use a product like Alodine to properly prep and remove the oxidation that forms on AL. After prep you need to get the epoxy on within 12 hours due to the fact that the AL will start oxidizing immediately after prep.
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what exactly is the product Chris? i assume it is not an acid? would this be a reasonable course of action on aluminum parts that would be very difficult or impossible to sand?
 
Treeslayer said:
what exactly is the product Chris? i assume it is not an acid? would this be a reasonable course of action on aluminum parts that would be very difficult or impossible to sand?
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Alodine is commonly used for aluminum.

A popular version of alodine is Bonderite

If you treat it correctly with the alodine system then no you do not have to sand. If you just wanted to prep something hard to sand then epoxy, a phosphoric acid treatment like Ospho is enough to de-oxidize the AL and allow it to stick. If you could sand it afterwards that would be better, but generally acid treatment if properly applied will allow paint to stick. You would apply Ospho the same way you apply it to steel including neutralizing it.

What I wrote in my post above is slightly misleading as Alodine is a multi part system that leaves a coated surface when finished and eliminates having to apply your primer immediately. I used alodine in the generic sense, as I refer to the cleaning/deoxidizing part as alodine when in fact that is incorrect. It's just what I've always heard it referred as. My apologies.
 
The Henkel stuff to etch and coat aluminum with Alodine is very good. Barry told me it's one of the best things for aluminum prior to epoxy.
I used something like it from DuPont many years ago where they called the second step a conversion coating but it was a yellow stain and looked like the Alodine. Today I use the Bonderite system when I want Alodine.
I have also had good results without etching and Alodine by sanding, cleaning and epoxy priming aluminum fabrications.
 
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Chris_Hamilton said:
Alodine is commonly used for aluminum.

A popular version of alodine is Bonderite

If you treat it correctly with the alodine system then no you do not have to sand. If you just wanted to prep something hard to sand then epoxy, a phosphoric acid treatment like Ospho is enough to de-oxidize the AL and allow it to stick. If you could sand it afterwards that would be better, but generally acid treatment if properly applied will allow paint to stick. You would apply Ospho the same way you apply it to steel including neutralizing it.

What I wrote in my post above is slightly misleading as Alodine is a multi part system that leaves a coated surface when finished and eliminates having to apply your primer immediately. I used alodine in the generic sense, as I refer to the cleaning/deoxidizing part as alodine when in fact that is incorrect. It's just what I've always heard it referred as. My apologies.
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im just leery of any acid.........i guess ill have to read up on how to neutralize.
 
Thanks folks, a customer (still trying to get full picture) sanded the pieces with 180 and hard areas with sctoch brite, cleaned (not sure with what yet) applied epoxy reduced (not sure of reduction) and not sure of the time after cleaning to apply epoxy. Long story short, customer has peeling from the aluminum, trying to piece problem and solution
 
Dutchman said:
Thanks folks, a customer (still trying to get full picture) sanded the pieces with 180 and hard areas with sctoch brite, cleaned (not sure with what yet) applied epoxy reduced (not sure of reduction) and not sure of the time after cleaning to apply epoxy. Long story short, customer has peeling from the aluminum, trying to piece problem and solution
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More than likely waited too long. Or he didn't get it clean enough with the sanding. Got to sand it really good to get the oxidation layer off. Assuming it was in bare aluminum for any time. If it was painted then that's different.
 
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You don't mention what epoxy was used. If it was SPI then the next time advise your guy to reduce no more than 10%. If it was another brand, all bets are off.
 
crashtech said:
We've done plenty of aluminum, stripped and sanded with sharp 80 grit, cleaned with 700 and shot with full strength epoxy on the same day. No comebacks so far since 2006.
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This is how we did the entire Argosy (Airstream) camper I painted. Half of it was done last year and half this year. It sits outside all year long but it’s been fine for at least one year so far.
 
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