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topic 4343

Prevent corrosion of Aluminum in salt water


An ongoing discussion from 2000 through 2015 . . .

(2000)

Q. I am doing maintenance on boats made out of aluminium. Have experienced corrosion pitting on bottom plating, etc. Boat is working in salt water. This is more serious on the inside of the plating. Need some solution to this problem. The boats are about 12 years old.

Suresh kapur
- Hilton Head South Carolina USA


wikipedia
Fluoropolymer
(2000)

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.

kalyan dhakane
Kalyan Dhakane
Mumbai, India


(2000)

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.

Jeff Watson
Jeff Watson
- Pearland, Texas


High Performance Powder Coating

(2000)

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.

Daryl Spindler
- Portland, Tennessee


(2000)

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.

Kalyan Dhakane Kalyan Dhakane
Mumbai, India


(2000)

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.

Teresa Sedmak
Everbrite, Inc.
supporting advertiser  
 Reno, Nevada

Grill protected with Everbrite



(2001)

Q. Have a 1997 aluminum 14 l/1 MonArk fishing boat that is developing numerous holes in middle section of hull. Planning to drill holes in floor of boat and fill hull with closed ceil flotation.

Good Or Bad Idea? If good, what to use and where to get. If bad, please explain. Thanks.

Ray Burns
- Charlotte Harbor, Florida, USA



Protecting aluminum from saltwater

(2002)

Q. What kind of primer and paint should I use to protect a cast aluminum fishing reel from saltwater corrosion?

John Segal
- Nanaimo, BC, Canada



Aluminum fence on salt water: best finish

(2002)

Q. Aluminum fencing, which is the best finish for location on salt water?

Holly Ferguson
- Miami Beach, Florida


(2005)

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.

Buddy Miller
- Claxton, Georgia, USA



Aluminium corrosion protection in seawater

November 24, 2015 -- this entry appended to this thread by editor in lieu of spawning a duplicative thread

Q. Hi

I created a diving light which will be a lot in sea water and a little bit in fresh water.
Aluminium used is the 5000 series.

I was thinking to anodize it and put power coating.

I want to get it a black finish and keep it during a couple of years.

Any suggestion to get aluminium good with salt water?

thanks

Eric Duhamel
- Canada


November 2015

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,

pic of Ted Mooney
Ted Mooney, P.E. RET
finishing.com
Pine Beach, New Jersey
Striving to live "Aloha"


4343_seawater_series
^ from http://www.nordhavn.com/resources/tech/images/Galvanic_Series.pdf ^

4343_eurospace_galvanic
^ from http://esmat.esa.int/Services/bimetallic_data/Bimetaltable/bimetalemf.html ^
November 29, 2015

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

William Doherty
Trainer - Salamander Bay, Australia


November 2015

thumbs up signHi William. You're probably right about Zinc anodes offering negligible (<1/4 volt) protection for 5xxx aluminum alloys.

Regards,

pic of Ted Mooney
Ted Mooney, P.E. RET
finishing.com
Pine Beach, New Jersey
Striving to live "Aloha"



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