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Discussion Starter · #1 ·
I had the cast aluminum binnacle components on my Crealock 34 stripped, prepped and painted with Awlgrip around 1-1/2 years ago. The paint is bubbling horribly at this point.

It is clear that the applicator botched the Awlgrip job as the finish never truly cured. However, it is also clear that despite abrading the surfaces with coated and non-woven abrasives and grit blasting with a fine glass media we were unsuccessful in ferreting out all of the previous corrosion.

Two questions:

1. Has anyone had experience successfully prepping previously corroded cast aluminum? How did you do it?
2. Does anyone have any insight into the relative merits of powder coating vs Awlgrip or other "wet" coatings?

Thanks.
Rich
S/V Kelly Rae
 

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Cast aluminum that has started to corrode is very difficult to paint and keep painted. That corrosion will continue to return and blister your paint. more likely the prep than the application of paint.
 

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I recently had mine powered coated, which is pretty much what they do at the factory IIRCC. I paid $125, not much more then what materials would have cost to do it myself using Interlux 2 part. Of course you could go cheap and use Rustoleom or something. Edson re-coating directions: Edson Pedestal Repainting Instructions

Don't mind the fish, but you can see how pretty that pedestal looks :)

 

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I had the Edson Binnacle repainted with Awlgrip 15 years ago by a professional painter in Rock Hall, MD. He apparently did it right as its still glossy white and not deteriorating at all. I assume its all in the "prep" in order for a good job. Sorry I don't have a photo of the binnacle.
 

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The only way I have ever found to keep paint on aluminium is to prime it with zinc chromate after thoroughly cleaning it first. Sandblasting is best but I've had good luck with sanding and wire wheels.

It's critical to get the zinc chromate on immediately after prepping the surface and wiping with solvent - aluminium starts oxidizing the minute you stop sanding.

I've had powder coating fail in one big piece - corroded under it and it came off like a mould of the piece.

Zinc chromate is what all the aircraft manufacturers use - it's the chartreuse colored coating you'll see on internal parts.
 

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My binnacle is 35 years old and there was some corrosion present when I rubbed it down. I did not remove all the old paint just feathered the edges. I applied two coats of red Berger undercoat that was marked as an etch primer and then two coats of oil based enamel. 3 years on and it is holding up.
 

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Discussion Starter · #8 ·
Thanks to all for your helpful responses.

Has anyone ever heard of treating the stripped and blasted aluminum with an acid of some form to clean out any last bits of corrosion? One paint company representative suggested to me using Sno Bowl (technically a bathroom cleaner but with HCl acid as an active ingredient. I have used it to remove ICW Mustache). I have also wondered if FSR or On and Off might help.

Any thoughts?
 

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...Has anyone ever heard of treating the stripped and blasted aluminum with an acid of some form to clean out any last bits of corrosion? One paint company representative suggested to me using Sno Bowl (technically a bathroom cleaner but with HCl acid as an active ingredient. I have used it to remove ICW Mustache). I have also wondered if FSR or On and Off might help.

Any thoughts?
The technical term is etching. I would choose products formulated specially for aluminum, for prepping the substract and remove oils, corrosion, etc.
Follow the instructions carefully.

Alumiprep 33 is one that comes to mind, another is Awlgrip Wash Primer CF.

http://www.solvents.net.au/index_htm_files/ALUMIPREP 33 (169315).pdf

http://www.awlgrip.com/products/primers/wash-primer-cf.aspx
 
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