Prevent corrosion of Aluminum in salt water

Fluoropolymer

A. Hi. You do a Xylan/Teflon/Dykor/Greblon, etc., fluoropolymer based coatings on your aluminium boat. That protects from salt water up to 20 Years.

A. The fluoropolymer is along the right track, for repair of these boats sand blast to white metal, apply the fluoropolymer coating as soon as physically possible. Contrary to popular opinion, Al corrodes almost instantly, the oxides will hurt adhesion. Under new production conditions I'd recommend chemical treatment before paint, but that may not be an option for you.

A. Wouldn't hard coat anodizing do a pretty good job of corrosion protection in salt water? If that wouldn't be sufficient I think hardcoat impregnated with a fluoropolymer would be great.

A. Hi. First you do sand/grit blasting, hard anodizing and then fluoropolymer coating. Hard anodizing giving a 60 micron thickness and afterward fluoropolymer coatings obtain up to 200 micron thickness. This system protects your boat minimum 20 years from salt water.

adv.,
Everbrite Protective Coating is a one part, clear coating that will protect the aluminum and other surfaces from salt water corrosion. It will also protect from U.V. oxidation. You can see more information by following the link to our website.

A. The term "powder coating" is so universal now that there is a connotation of "magic" implied. Like most coatings the devil is in the details. Powder coatings are by far the best coating for salt spray conditions, but the chemistry, manufacturer of powder, quality testing at the applicator and the pretreatment process used are the critical elements. The surface preparation is so critical and the most likely item to be abused. I recommend a 5 stage pretreatment with attention to proper cure. The evaluation of the applicator is often done as part of a powder manufacturer certification process. I recommend seeing these documents. Beware. BUT there are 10, 15 and 20 year warranties available. Good Luck.

A. Hi. You're on the right track, although chromate conversion coating before the powder coating would probably be as good as anodizing, and less expensive, and offer conductivity which you might want ... for example, I think a tiny replaceable zinc anode for salt water would not be a bad idea, although magnesium would be better for fresh water.

Regards,

^ from http://www.nordhavn.com/resources/tech/images/Galvanic_Series.pdf ^


^ from http://esmat.esa.int/Services/bimetallic_data/Bimetaltable/bimetalemf.html ^

Well, I am not sure how a Zn anode could be expected to protect Aluminium, though I am willing to listen and learn.
I would think that the best protection could be to select a marine aluminium as a base, give it a chromate pretreatment and then give it a fusion bonded epoxy finish coat.
Hope this helps,
Regards,
Bill

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Hi William. You're probably right about Zinc anodes offering negligible (<1/4 volt) protection for aluminum alloys. The 5xxx series are the marine grade, so Eric is off to a good start :-)

Regards,

Ted Mooney, P.E. RET
Striving to live Aloha
finishing.com - Pine Beach, New Jersey
November 2015

A. Hi John,
Any coating, once chipped, will expose the parts to the seawater again so you've got to do something UNDER the paint too.

Chromium conversion coating is not only a good protection against corrosion, it helps the paint adhere better too, and prevents it bubbling and peeling if scratched. As a bonus, it doesn't require electrical contact, so would be possible to basket-process.

The other option is anodizing; the parts would need to be racked appropriately, and this is done by hand and can be time consuming and therefore expensive.

You'd want to weigh one time consuming process against a double process before committing.

Stainless steel isn't an option?