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Old 18-01-2021, 10:09   #1
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Aluminum Protection

I have a keel stepped sailboat. I removed the aluminum cabin top mast support to rebed it and found corrosion on the aluminum. I've cleaned it up but I'm wondering if there is something I can put on it to help prevent future corrosion
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Old 18-01-2021, 10:23   #2
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Re: Aluminum Protection

You can slow the onset of the corrosion with PERFECT preparation and coatings, but it will always come back, eventually.

I just went through this same problem on a customer's boat. After much deliberation over which coating/procedure to use, our fiberglass man brilliantly suggested that he use the aluminum collar as a mold to make a new FIBERGLASS collar.

Problem solved.

Steve
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Old 19-01-2021, 05:00   #3
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Re: Aluminum Protection

I'm touching up corrosion on my spreaders (which looks a lot worse than it is) with an etching primer then I'll paint it with an epoxy(?) paint (I have a tin of it in my workshop) I think it is called Metalshield

This is it.


Metalshield 300g Etch Primer Spray Paint Light Grey ...
www.bunnings.com.au › metalshield-300g-etch-primer-sp...

Anti-corrosive metal primer · Protects against rust and corrosion · Etches surface for optimal topcoat performance · Ideal for aluminium, copper, brass, stainless steel ...Minimum Temperature for Use: 10

Recommended Surfaces: Aluminium, copper, ...
Coverage Area (m2/L): 1.5
Container Size (L): 0.3
$13.40

Metalshield Premium Aluminium - Dulux Protective Coatings
www.duluxprotectivecoatings.com.au › products › ranges

METALSHIELD® PREMIUM ALUMINIUM is an alkyd enamel paint formulated with metallic flake to impart a bright metallic finish to a range of suitably primed metal substrates, such as mild steel, galvanised steel and aluminium. METALSHIELD® PREMIUM ALUMINIUM has excellent reflective properties and weathering resistance.
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Old 19-01-2021, 09:31   #4
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Re: Aluminum Protection

Just for clarification, you will spray or paint on the metal shield to etch the aluminum to prepare it for the application of epoxy. The epoxy is to fill and smooth out the surface. Correct?
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Old 19-01-2021, 15:14   #5
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Re: Aluminum Protection

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Originally Posted by weephee View Post
Just for clarification, you will spray or paint on the metal shield to etch the aluminum to prepare it for the application of epoxy. The epoxy is to fill and smooth out the surface. Correct?

I'd get expert advice on that.

I'd get rid of all corrosion by wire brushing (or sanding) and then straight away hitting it with the primer. If you leave it too long the aluminum will oxidize before you prime it (apparently that is not good)

After priming it logically you would the smooth the area with epoxy(?) and then paint it. But DYOR! (and talk to the people who know eg paint manufacturer)
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Old 19-01-2021, 18:24   #6
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Re: Aluminum Protection

The primer is described as an "etch primer" which usually means that the etchant is mixed in with the coating so that the etching and wetting by the coating can take place on the metal surface in the oxygen free environment provided by the coating of liquid primer.

The purpose of the etch primer is to provide good adhesion to the metal whilst also providing a good surface for the following coats to adhere to, epoxies do this well however they are porous and in the marine environment require over-coating with a more waterproof coating layer to prevent moisture access to the metal surface.

For small aluminium items powder coating is sometimes the best solution.
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Old 19-01-2021, 19:13   #7
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Re: Aluminum Protection

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.......r the following coats to adhere to, epoxies do this well however they are porous and in the marine environment require over-coating with a more waterproof coating layer to prevent moisture access to the metal surface.

For small aluminium items powder coating is sometimes the best solution.

What you say fits in well with the recommendation on the side of the tin of Metalshield (Obviously I'm not using epoxy)


Dulux 1L Metalshield Premium Industrial Aluminium Topcoat ...

www.bunnings.com.au › dulux-1l-metalshield-premiu...



METALSHIELD® PREMIUM ALUMINIUM is an alkyd enamel paint formulated with metallic flake to impart a bright metallic finish to a range of suitably primed metal substrates, such as mild steel, galvanised steel and aluminium. METALSHIELD® PREMIUM ALUMINIUM has excellent reflective properties and weathering resistance.
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Old 19-01-2021, 20:52   #8
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Re: Aluminum Protection

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Originally Posted by coopec43 View Post
What you say fits in well with the recommendation on the side of the tin of Metalshield (Obviously I'm not using epoxy)


Dulux 1L Metalshield Premium Industrial Aluminium Topcoat ...

www.bunnings.com.au › dulux-1l-metalshield-premiu...


METALSHIELD® PREMIUM ALUMINIUM is an alkyd enamel paint formulated with metallic flake to impart a bright metallic finish to a range of suitably primed metal substrates, such as mild steel, galvanised steel and aluminium. METALSHIELD® PREMIUM ALUMINIUM has excellent reflective properties and weathering resistance.
I think the aluminium is included for mainly decorative purposes. Zinc is a more usual inclusion for anti corrosive purposes.

It is surprising where one finds aluminium. I was told that it's included in the plastic from which shade cloth is woven to provide UV protection and it's one of the primary components for solid rocket fuel.

When I was young I worked in a hardware store and we sold it in powdered form for inclusion in various things including paints and putties.
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Old 20-01-2021, 04:01   #9
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Re: Aluminum Protection

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Originally Posted by RaymondR View Post
I think the aluminium is included for mainly decorative purposes. Zinc is a more usual inclusion for anti corrosive purposes.

It is surprising where one finds aluminium. I was told that it's included in the plastic from which shade cloth is woven to provide UV protection and it's one of the primary components for solid rocket fuel.

When I was young I worked in a hardware store and we sold it in powdered form for inclusion in various things including paints and putties.



From memory aluminum powder and sulfur was the best fuel for our home made rockets.
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