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When painting aluminum, does every bit of old paint need to be removed before gong through the alumaprep / alodine / paint process? Please say no.....

We've sanded everything pretty well, but some of that old paint is not coming off completely without a big battle. Talking about window frames here.

Thanks!

Sean...

I removed all the black paint the previous owner put on the window frames and the toe rail with regular paint remover, then scrubbed all the surfaces with warm water, then followed Capt Patricks method of cleaning all bare Al surfaces with AlumaPrep, followed by a rinse immediately with warm water, followed immediately when dry with a coat of Alodine. The next day I applied another coat of Alodine. (Both Alodine coats were sprayed.)

I finished the window frames with two brushed on coats of Aluminum paint. Finding that you can't brush on aluminum paint without having the job look streakey and therefore crappy I sprayed two additional coats of aluminum paint for a total of four finish coats on the window frames.

On the rub rails I have applied two coats of epoxy primer over the Alodine, and will finish off with probably two or possibly three coats of final hull paint (In my case it will be AwlCraft 2000.) when the painter does his thing.

I have been told that you should not try to fill any depressions in aluminum with anything, since salt water will find it's way between the filler and the aluminum and additional crevice corrosion will occur, so I left the pits, etc, as I found them (in the rubrail). Most of them will be covered with the 3/4" wide stainless rub rail cap I will apply later anyway.

Everyone tells me after painting aluminum you will see peeling and corrosion after a couple of years, and I believe them, but I decided to do as good a job as I can while the boat is hauled and I have scaffolding in place for easy access.

Damn I was hoping not to spray. That a lot of stuff to mask off. I wonder if a polyurethane paint would be better to brush on than the enamel "hammertite" that I ordered

As I recall I bought the Al paint from Hammerite.. one quart can and two spray cans. I emptied both spray cans and then used a spray gun to finish the job.

My problem with brushing was caused by the fact that aluminum paint gets dark and light streaks (I suspect due to how the metal flakes orient themselves) as you work it with a brush. If you use regular colored paint I think brushing would be fine.

Are you using hammered finish or regular? I imagine that hammered finish would hide any pitting pretty well.

Sean, it seems to me you have two separate issues.

The first being the alodine application. You can apply the alodine in this condition, it will form the chem film only on the areas you have exposed. The paint covered areas, in theory, should still have anodize in place and should be even better protected than the alodined areas.

The second question seems to be about how the paint will adhere to the areas that still have the old paint in place. I think that you will be fine. But there are a lot of guys here with more experience than I have and I'd like to see if they agree.

But I am pretty confident you have no problem.

John

I bought the matte black Hammerite brush paint, not the metal flake stuff. Not using glossy paint should help me out too. So I'm going to give it a whirl...

I helped a buddy redo his rub rail a couple of years ago , did the alodine process. And brushed on van aluminum product by Awlgrp, it looked great and held up untill the untreated areas on the backside of the rails worked their way outward, other than that the treated areas still look great and extremely durable

Let us know how it goes.