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PostPosted: Fri Oct 14, 2011 5:38 pm 
I'm looking at a Grand Raid 520 with a skin in pretty good shape but the frame needs repair. It appears that the frame wasn't rinsed and/or dried before storage and there's significant saltwater corrosion of most of the brass fittings and some of the moving fittings are frozen. I don't think the corrosion is deep enough to jeopardize the fitting strength and after a thorough cleaning should be OK. So here are my questions.

1. What's the best way to clean the saltwater corrosion? I've seen suggestions from vinegar+salt+flour to commercial brass cleaners such as Brasso or Noxon.

2. If you take good care of your boat, well-cleaned-rinsed-dried after saltwater use, do you get much corrosion of the brass fittings anyway? I don't need it to shine, I just don't want to see the blue-green copper corrosion.

3. Have any Nautiraid owners sealed their brass fittings? If so, what sealant did you use?

Thanks,


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PostPosted: Sat Oct 15, 2011 4:24 pm 
Almost all of the brass fittings on my Raid II are discolored with a brownish patina. I replaced some of the brass screws that were brittle and corroded with brass and stainless. I've seen similar corrosion / discoloration on other boats. I think it's the nature of brass when exposed to salt even if you rinse out the boat after salt water use. Have not tried to clean the fittings, and when I re-finish the wood, some varnish gets on the brass which may add some protection.

Rob


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PostPosted: Sun Oct 16, 2011 6:39 am 
lord high faltbotmeister

Joined: Thu Sep 06, 2007 8:05 am
Posts: 824
Location: atlanta, georgia
The surface oxides on brass gives way to almost any kind of metal cleaner, including a mixture of a mild acid (like lemon juice) and a mild abrasive (like flour or salt). But no matter what you do, the oxidization will return if the brass is exposed to air and any moisture at all, whether salt or not. The only way to stop this is to create a barrier from the elements. Lacquer is often used, but I think it would be worse than nothing in your case, as it tends to crack and chip in a dynamic environment. You might try a coating of wax or oil to help delay the oxidization but don't expect to stop it.
Hope that helps.
g

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PostPosted: Sun Oct 16, 2011 9:40 am 
Site Admin

Joined: Thu Apr 14, 2005 12:34 pm
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Location: Southeast Michigan
I'd agree with the wax suggestion. A shot of Boeshield would be good. Replace the brass screws with new ones where possible. They can become devitrified and weaken even while looking okay. Don't use stainless screws on brass fittings, as you'll accelerate electrolytic corrosion. You can use stainless screws in areas where they serve as anchors to rubber hinges and straps.

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PostPosted: Sun Oct 16, 2011 11:47 pm 
My knowledge of brass corrosion is limited but I believe the brown patina is from oxide formation from brass in contact with air. The copper oxide layer is protective and reduces further oxidation. The blue-green corrosion which I have is from copper chloride formation with the chloride coming from seawater. The type of oxidation actually accelerates further corrosion of the brass fittings. Brown=OK, blue-green=bad.

Brass corrosion in seawater has been known for a few hundred years so it's a bit puzzling that Nautiraid has used brass fittings for 70+ years and has only recently switched to stainless steel.

I'll use the mild acid+abrasive and then baking soda to neutralize any residual acid. After I have a clean, dry surface, I'll try some different sealants and see what works.

Thanks very much for your tips and suggestions.


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PostPosted: Mon Oct 17, 2011 11:13 am 
Site Admin

Joined: Thu Apr 14, 2005 12:34 pm
Posts: 1754
Location: Southeast Michigan
One additional thought: Bronze screws would be even better than Stainless steel, particularly where parts are likely to be immersed continuously.

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PostPosted: Mon Nov 21, 2011 1:38 am 
Here's an update and some tips that seemed to work for my blue-green brass corrosion of Nautiraid fittings. An acidic solution will help dissolve the blue-green oxidation. The baking soda at the end makes sure any residual acid is neutralized.

Lemon juice or vinegar is acidic enough to remove much of the corrosion. However, the
best-easiest corrosion cleaner was vinegar+salt+flour.

No guarantees but this is what I did.

Recipe: 1/2 cup white vinegar+3 tsp salt+ enough flour to make a runny paste.
1. Wet brass surface with water and apply paste with toothbrush,
2. Scrub paste with toothbrush/brush on problem areas for a few minutes
3. Let paste sit for >20 minutes (important that paste completely covers area you want to clean, the long contact time of the paste is what makes it more effective)
4. Completely rinse paste off with water, need to really get ALL the paste off and then rinse well.
5. Soak for >10 minutes in water with baking soda, > 5 tbs/gallon, this neutralizes any residual acid
6. Rinse again in water and then air dry completely.

This didn't completely remove all the corrosion, but it did get rid of all the blue-green gunk. Areas with minimal corrosion (brown patina) look like new brass, areas with major corrosion (blue-green) now look like brass with some oxide oxidation (brown patina). The more corroded areas still have some major pitting but I think I've stopped the major corrosion.

After everything dries, I'll probably seal it with spar varnish as I touch up the wood areas that need repair.

Hope this help other Nautiraid owners.
T


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