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Old 21 March 2010, 12:09   #1
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Best corrosion protection for aluminum in saltwater

As I just reached the 55 yr milestone I decided to buy a house in a warmer climate so I bought one in Punta Gorda fl. Being very close to the gulf (800 ft) I was kicking around the idea of hauling the ole War Machine down south to use. My only concern is the corrosion issue with saltwater use. Being as the boat is nice and pretty now with fresh powdercoating on the seat hardware and elsewhere I am seeking advice from those of you out there who have run aluminum hulled boats in seas and what you have used to reduce corrosion and what you might recommend as advice. Keep her on the Great Lakes? Or haul it down?
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Old 21 March 2010, 16:40   #2
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I certainly wouldn't let it stop me from using it, as far as your powdercoating goes the only measure you could take that I can think of is to just wash the boat down with fresh water at the end of a day out. But I think that it would go a long way towards keeping the corrosion at bay.
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Old 21 March 2010, 19:27   #3
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I had an ally yacht some years back which we used extensively for blue water cruising and for me if money was no object it would always be my material of choice.

From my experience with ally you can avoid many problems by careful design and build but your boat is beyond that stage and you probably canít change much so that isnít very helpful. As long as careful attention has been made to avoid wherever absolutely possible mixing metals then you are off to a good start.

I assume you are keeping her afloat so another thing to consider is where she is being berthed. I would think carefully about leaving her against steel pilings for any period.

A good marine engineer, naval architect or boat builder with experience in ally would no doubt give you sound advice. Ally is not so common a material for boat construction in the UK but he Ozzies and Kiwis use it and I thought you guys in the states were fairly familiar with it. I think I saw that there were some Canadian built ally ribs about so it might be an idea getting in touch with them.

I have heard of horror stories where ally yachts have sunk on their berths but have never seen this. My yacht did multiple Atlantic crossings and a circumnavigation with no problems and after 3 years had almost no wastage on her sacrificial plates.

Jon
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Old 08 April 2010, 11:25   #4
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Powder coated aluminum parts will resist corrosion if the aluminum is treated before painting. I spent 15 years with a manufacturing company in the diving industry and gained quite a bit of experience from conditions all over the world. We tried once to just zinc chromate our aluminum parts prior to powder coating, that was a total mess with a lot of returns. The best was to anodize with a sealer but more importantly not to contaminate by touching the parts without gloves or well cleaned hands. Anything assembled on the parts with screws was stainless but also we used zinc based grease. We used loctite for a while but it ate away at the anodizing in the thread holes just enough for corrosion to start. But by far the very best is to always rinse and wash with fresh water.
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Old 08 April 2010, 11:51   #5
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Also depends on the alloy used. I think you'll see most problems in crevices and such rather than on the plate, especially in areas where dissimilar metals are in contact (think fastening hardware.) Might invest in a *lot* of aluminum-safe anti-seize, and apply it whenever you pull something apart.

Keep your zincs clean and fresh to avoid any electrolysis problem.

5000 series Al doesn't really need much protection; just let it turn its normal powder gray and you're done. 6000 series should be pretty close to that.

FWIW, I don't do anything to mine except give it a quick hose-down after a weekend n the water.

Not much help, but I don't think you've got a lot to worry about...

jky
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Old 08 April 2010, 13:17   #6
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Quote:
Originally Posted by jyasaki View Post
Also depends on the alloy used. I think you'll see most problems in crevices and such rather than on the plate, especially in areas where dissimilar metals are in contact (think fastening hardware.) Might invest in a *lot* of aluminum-safe anti-seize, and apply it whenever you pull something apart.
I use tefgel
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Old 08 April 2010, 21:53   #7
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If you use stainless screws from a hardware store they will rust real fast. Stainless hardware for marine use has been processed by "passivation treatment". As for aluminum, 6061-T6 alloy s quite resistant.
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Old 08 August 2010, 22:54   #8
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Many alum boats...

I have had several aluminum boats out here on the Chesapeake Bay, not quite as salty as the Gulf, but salt is salt. Here is what I do:

1) First part of year I clean it up good. Then apply some WD-40 to screws, seams, and other such parts. If I find any screws or such that are rusting/corroding, I pull them out (assuming you can)...and replace them with new marine grade stainless. Mind you, I have only had to replace things about 5 times over 25 years...cost me about $30.

2) There are lots of choices for plates...just find ones that work for your boat. These should be replaced at least every 2 years, or every year...depending on deterioration

3) After EVERY outing, wash down EVERYTHING with fresh water.

4) After you wash it with fresh water, give another quick bath with something like "Salt Away"...just attached the connector to the hose and spray away. You can just leave it on the boat. Remember, plain water will NOT take out all the salt, it can create bonds with the metal...using something like Salt Away will take away those last bits of salt...also great to use when flushing the motor (and it is environmentally safe to boot).

5) At the end of the season, do #1 again.


Thats' it...once you get a rhythm down, you are talking about a whopping 10 minutes for wash down, and maybe 1 hour prep-time at the first/last part of the year. 25+ years from now it will still be working/looking fine...hell, I still have a 1950's 7.5hp Evinrude I put on my sons first boat (the one I mentioned above)...damn thing probably weighs as much as he does!
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Old 09 August 2010, 06:37   #9
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Limit the amount of steel on the outside of the boat. If you have a stainless steel props and want to stay with them, be sure to have a zinc anodes as close as possible to them. No copper.
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