Cascade Crew

[jchaussee]

Tips and tricks on geting paint to adhere to aluminium. I am painting the channels the the t top seals go into and I have not had good luck with painting aluminium. Seems to just Peel off.

[flea]

Lightly sand, use good primer as per manufacturers directions and topcoat.
Allow it to warm up before painting. Paint doesn't generally like cold.

[jchaussee]

Is there a preferred primer for aluminium? I have painted alot cars and parts in my life buy aluminium has always got the best of me.

[flea]

When I was in the USAF painting aircraft we used epoxy primer. It held up to 450 kts lol. It wasn't applied heavy and dark for painting right afterward.
Applied in a thin coat, and topcoat as soon as practical. If it was allowed to sit for more than a day, sanded and start over.
Thats the way we did it anyway. Thin coat of epoxy primer and paint within a few hours and good for jet aircraft.

Chelsea might weigh in, she paints cars and has more recent experience.

[chevymad]

Aluminum needs to be etched and treated before painting. At home you won't be able to do this, but you can get a special primer.

http://www.amazon.com/Moeller-Zinc-Chromate-Primer/dp/B004EPWY2Y/ref=pd_cp_hi_2

[jchaussee]

Cool guys. I appreciate the help. I have cleared our my garage over the last week and I now can finally finish a few small projects.

[flea]

We never etched the AL before painting. However, you can etch at home, Alodine is the product you are looking for. look for it at Aircraft spruce and specialty, http://www.aircraftspruce.com/catalog/cspages/alodine1201.php it is 18.00 a qt. We only used it when the metal surface was to left unpainted because of the cost. I mean 18 a qt, could you imagine doing an entire B-52??
You could try wiping down with white vinegar, that works on galv. metal to etch the surface.
Zinc Chromate would probably be just as easy though.

[chevymad]

The processes I was looking up were at least 5 stages. Some with recirculating distilled water washes. Plus you'd need to buy the chemicals for each stage. Just much easier to use the correct etching primer. There's also more to etching then just using an acid. Acid gets the oxidation off the surface, but now you need to put a coating on it before it re-oxidizes. This is where the phosphate or chromates come in.

Kinda funny.. you went to aircraft painting, and I went to marine. I would think the marine would be a tougher environment requiring more corrosion protectoin.

[jchaussee]

Now that I think about it. Are the t top channels galvanized or aluminium. I thought aluminum because of weight, but it looks like it could be galvanized?

[chevymad]

I've never had a ttop so wouldnt know. Do they rust? Are they magnetic?

[flea]

I went aircraft cause it's what I'm most familiar with. That alodine is more than just the acid wash. It both etches and provides a chemical barrier to corrosion. It leaves the aluminum a gold color. Corrosion is chemical process. You need to have an electrolyte, an anode and a cathode. Both of those are the metal in question, and eliminating them is not generally possible. The electrolyte is typically moisture. Paint is used to form a mechanical barrier between the metal and that moisture, Alodine is a product name, but it is generally speaking just a method of anodizing the aluminum. That creates a chemical barrier between the surface and the atmosphere.

Anyway, its getting way off topic now.

Sand the parts, use zinc-chromate and paint. Don't paint if the surface temp is too low.

[chevymad]

Wasnt saying the alodine was acid.. but the vinegar is.

[flea]

I think the channels are Aluminum, They are way light and pretty flimsy feeling.
When I changed the seals on my tops, I just cleaned 'em up real good and primed the crap outta them then reassembled with liberal dose of sealant both under the channel and between the rubber seal and the channel.

[flea]

[IROCDave]

Go here -
http://www.wescopbe.com/store_locator.htm#RENTON

They will have what you need if it is automotive.