Powder coated aluminium- cleaning up and repainting

Kelpie

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The rudder stock for my dinghy is (or was) powder coated aluminium. It was badly damaged and bulging with corrosion under the coating.
I've ripped off all of the remaining powder coating, leaving the aluminium basically intact but covered in grotty, crumbly, white/grey corrosion products.

1- what's the best way to clean up and prepare the surface for a new finish

2- short of having it powder coated again (not an option) what would be the best type of finish? I've got a little Hammerite, or I've got International Perfection two pack. I think the latter would need a primer.
Open to other options too- I don't suppose I can leave it unfinished. I guess I could varnish it 🤔😁
 

Kelpie

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Oh here's another option, I've got a can of galvafroid... that would be a bit quicker and easier...
 

Neeves

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If you have one stainless rotating brush on an angle grinder will remove the corrosion, get back to bare metal and prepare the surface for coating. As on the windlass thread then Hammerite and your tins of 2 pack. If you touch the surface after you attack with the wire brush it will feel nasty - it catches your skin, perfect key for the primer. But after the stainless brush on the angle grinder, wash with fresh water, wipe with alcohol (to remove grease) .... not your best Malt :) and don't touch is agin - your fingers will leave grease on the surface (so wear gloves). You want to remove ALL the white powder.

You cannot leave it - it will continue to corrode.

If this all works but the thicknesses are a bit skinny next time you are in civilisation re-stock with Hammerite and maybe give the 'repair' another coat - unless it has started to bubble - in which case you start again.

Paint has micro-porosity (even powder coat) more coats give you a better chance to completely seal the surface

Jonathan
 
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B27

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Epoxy sticks well to aluminium.
A paint like Durepox might be a good answer.

Or just warm it up, apply a couple of coats of WEST or SP, then spray it white to keep the UV off.
 

Kelpie

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Epoxy sticks well to aluminium.
A paint like Durepox might be a good answer.

Or just warm it up, apply a couple of coats of WEST or SP, then spray it white to keep the UV off.
Ooh that's an idea, I've got a good stock of epoxy. So maybe epoxy as a primer and then 2-pack top coat?

I want to avoid too much build up though. It's a rudder stock and the rudder blade is a fairly snug fit between the cheeks (if that's the right term!). I realised I had a problem when I was struggling to get the rudder to swing up, the bubbling had swollen it up so much that everything was starting to bind.
 

Neeves

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Ooh that's an idea, I've got a good stock of epoxy. So maybe epoxy as a primer and then 2-pack top coat?

I want to avoid too much build up though. It's a rudder stock and the rudder blade is a fairly snug fit between the cheeks (if that's the right term!). I realised I had a problem when I was struggling to get the rudder to swing up, the bubbling had swollen it up so much that everything was starting to bind.
Its as good a solution as any.

Your problem might be the snug fit, engendering abrasion. You need to watch the places you repair to make sure whatever you decide to use remains integral - or it will start to corrode.

Jonathan
 

rogerthebodger

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The way I would refurbish an aluminum item would be to grio blast back to bear metal then have the aluminium anadied as a protective coating.

If you wish to have it coloured you can colour the anadiing what ever colour like

One thing I found with aluminium coating is that any flour / damage to the coating will promote corrosion of the aluminum under the coating
 

Kelpie

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The way I would refurbish an aluminum item would be to grio blast back to bear metal then have the aluminium anadied as a protective coating.

If you wish to have it coloured you can colour the anadiing what ever colour like

One thing I found with aluminium coating is that any flour / damage to the coating will promote corrosion of the aluminum under the coating
I don't that option is available to me here.
 

Kelpie

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Well this is tedious.
I don't suppose I can use oven cleaner or something like that to strip off the corrosion? There's so many little corners and hard to get to bits on this casting.
 

rogerthebodger

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Well this is tedious.
I don't suppose I can use oven cleaner or something like that to strip off the corrosion? There's so many little corners and hard to get to bits on this casting.

I have used swimming pool acid to remove corrosion from both steel or aluminum.

Hydrochloric acid or phosphoric acid
 
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