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Old 23-09-2016, 19:59   #1
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Aluminum Mast and Zinc Cold Galvanize Spray

Thanks for any help.

The spreader holders (?) are aluminium on my mast and show a lot of corrosion.

Can I use rustoleum zinc cold galvanising spray on them ?

arch
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Old 23-09-2016, 20:40   #2
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Re: alualuminium mast and zinc cold galvanise spray

no !

In Contact with Other Metals | American Galvanizers Association
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Old 24-09-2016, 00:32   #3
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Re: alualuminium mast and zinc cold galvanise spray

Galvanizing is for iron.

For Aluminum, depends on how bad they are. We have carefully polished pitted aluminum, then filled it with epoxy and micro balloons to fair it, then etch primer, epoxy primer, and epoxy painted it. That will slow down the corrosion, but anywhere s/s goes near it, you need to isolate it from galvanic corrosion. Old inner tubes work well, silicon chopping sheets, too. Do not depend on lanolin, or anti-seize for isolating large areas.

Use Duralac, Tef-gel, or Shiny anti-seize for screws. If your spreaders through bolt into the pockets, it is probable the s/s bolts were not isolated from the aluminum. You can use nylon washers, in between, that may help.

For a while, some people were using s/s bands around aluminum masts, with s/s spreader pockets, but aluminum spreaders. Said masts had frequent failure rates -- at the spreaders. Not a big surprise. Just be aware of dissimilar metals corrosion, and isolate what you can. You'll have to be creative.

Good luck with it.

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Old 24-09-2016, 03:29   #4
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Re: alualuminium mast and zinc cold galvanise spray

Greetings and welcome aboard the CF, Arch.
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Old 24-09-2016, 04:34   #5
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Re: alualuminium mast and zinc cold galvanise spray

Welcome to CF Arch !
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Old 24-09-2016, 15:11   #6
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Re: alualuminium mast and zinc cold galvanise spray

Quote:
Originally Posted by boatpoker View Post
Not so fast with the NO!
First, what is referred to as "cold galvanising" is not the same as a hot dipped zinc coating we love on steel.
Paint is paint, not liquid metal. There is some type of body there in the coating that does the adhesion. After all, we can apply an epoxy copper antifoam to aluminium OK, but not a copper rich conventional antifoul.
It is all in the binder and the level of organic zinc in the coating.

In reality - "Read the label!" OK, perhaps the data sheet and/or contact the tech department at the paint company. They are the ones with the product knowledge.
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Old 24-09-2016, 15:24   #7
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Re: alualuminium mast and zinc cold galvanise spray

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Originally Posted by Djarraluda View Post
Not so fast with the NO!
First, what is referred to as "cold galvanising" is not the same as a hot dipped zinc coating we love on steel.
Paint is paint, not liquid metal. There is some type of body there in the coating that does the adhesion. After all, we can apply an epoxy copper antifoam to aluminium OK, but not a copper rich conventional antifoul.
It is all in the binder and the level of organic zinc in the coating.

In reality - "Read the label!" OK, perhaps the data sheet and/or contact the tech department at the paint company. They are the ones with the product knowledge.
Any coating, even paint on aluminum can cause catastrophic damage whic is why there are very specific coatings for aluminum. Many paints contain some metallic compound (something like titanium dioxide among others). Unless you are knowledgeable about these compounds and exactly what is in that coating you should not apply it to aluminum ...... PS I'm a Certified Corrosion Analyst and have a clue as to what I'm talking about.

Sure contact the mfg. and get it in writing (not likely) from them that the coating is compatible with aluminum.
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Old 24-09-2016, 17:28   #8
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Re: Aluminum Mast and Zinc Cold Galvanize Spray

Wattyl kill rust etch primer/ then coat with Wattyl kill rust epoxy gloss enamel top coat aluminium / and hope corrosion hasn't already gone through the mast section / pit marks on top can be the tip of heavy corrosion inside
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Old 24-09-2016, 19:11   #9
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Re: Aluminum Mast and Zinc Cold Galvanize Spray

Zinc chromate, the only corrosion resistant primer to use on aluminum. All aircraft are primed with zc before paint, works even on seaplanes.
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Old 24-09-2016, 20:18   #10
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Re: Aluminum Mast and Zinc Cold Galvanize Spray

A dremel does a great job of cleaning out all the pits back to clean metal, a combination of the little die grinder, and the stainless wire brush works well. Then a quick stainless wire brush just before painting with your choice of primers and prep coats, or just leave bare and use duralac or similar. If the pits are too bad a new aluminium sleave can be made to cover the whole area, and it can incorporate new spreader bases , and also a doubler plate for the shroud attachments.

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Old 24-09-2016, 20:33   #11
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Re: Aluminum Mast and Zinc Cold Galvanize Spray

As important as the right paint and prep solutions is getting the area scrupulously clean of all corrosion products first, and getting paint on before new ones form. Even 5-10 minutes is enough for oxidation to start to form and inhibit the bond. The gougeon brothers talk about wetsanding the wet epoxy just after its applied and right through to the aluminum to scour away the flash oxidation, maximising bond.
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