Aluminum in Salt water

Corrosion, Paint, Through Hulls, etc.
fighterpilot
Tin star
Posts: 35
Joined: Fri Apr 28, 2017 8:03 pm

Aluminum in Salt water

Post by fighterpilot »

Seriously considering a Marinette Boat. 1982 37 sedan. Will be docked in brackish saltwater. I have searched for information regarding Aluminum boats in salt water and get mixed opinions. What is the recommended bottom paint for such an environment? At least it won't get water logged, but is the interior of the hull painted as well, since pumps don't always get it dry.

Also asked in another post, what were the fuel tanks on a 1982 37 foot sedan?? How about prop size and pitch? Thanks
jralbert
Site Admin
Posts: 885
Joined: Fri Jul 11, 2014 9:15 pm

Re: Aluminum in Salt water

Post by jralbert »

My '88 32' Fly Bridge sedan was in brackish Chesapeake Bay (halfway between Atlantic Ocean and north end of the bay). No corrosion issues with the boat properly protected and with a Capac Monitoring system. Interior of the boat was not an issue as long as there was no stray 12V DC current - there wasn't. Stray DC is the thing to fear.

Interior was factory coated with some weird gunky stuff which flakes off after some years and as far as most of us have been able to determine, serves only to deaden sound which can be annoying when you try to sleep as water laps against hull. It was a coal tar concoction, overpainted with a grey aluminum paint.

Fuel tanks were aluminum and in good shape when I sold in 2011.

I used Trilux 33 and it did the trick. I had also used ZO No Foul but found the similarly priced Trilux did a better job for me (the other company may have changed or upgraded formula so I can't tell you what's best today. I keep urging forum users to experiment, coating an object with different brands and comparing results. And posting their findings).

props were Nibral 16 x 15, cupped.
-joel-
former owner 1988 '32 FB Sedan
Chesapeake Bay
twin 318 / 240 hp
Potomac MD
User avatar
Busia
Royal Aluminum Star
Posts: 406
Joined: Tue Jul 15, 2014 12:21 am

Re: Aluminum in Salt water

Post by Busia »

The Trilux 33 works good, but I won't use it because it has copper in it. They say no tin, but do admit it is copper based.
BUSIA
located in Ketchikan, Alaska. Gods country
32 foot Marinette (no fly bridge)
twin 350 Crusader (Chev 350) engines
1:1 Borg Warner velvet drive transmissions
Closed cooling (antifreeze in the engine)
Proud to be retired IBEW and an A+P
jralbert
Site Admin
Posts: 885
Joined: Fri Jul 11, 2014 9:15 pm

Re: Aluminum in Salt water

Post by jralbert »

Sorry, but you are misinformed. If it contains copper, it is a derivative, not pure copper. It's made especially for aluminum (and can be used on other materials as well). Many of us have used it for years with no ill effect. You have reasons important to you for not using it but those of us who have used it in brackish water were pleased with the results vs other products. Long time ago, there was an anti-foulant containing tin, but that was banned due to effect on sea life. Here's a full pdf sheet from Interlux on boat paints.

http://www.yachtpaint.com/LiteratureCen ... 17_web.pdf

BTW, they do make other stuff for aluminum boats and if one is interested in their brand and want a recommendation, I suggest calling the tech reps who are knowledgeable. years ago, they guided me thru a re-paint process following sandblasting the bottom.

(PS: one other brand uses cuprous sulfate which sounds like like copper but is not the harmful element)
-joel-
former owner 1988 '32 FB Sedan
Chesapeake Bay
twin 318 / 240 hp
Potomac MD
fighterpilot
Tin star
Posts: 35
Joined: Fri Apr 28, 2017 8:03 pm

Re: Aluminum in Salt water

Post by fighterpilot »

Mailed a contract offer on the Marinette 37 sedan today. Now looking for a surveyor. I am familiar with a fiberglass survey but for an aluminum boat i doubt that one goes around tapping the hull with a small hammer. How does a surveyor check the hull thickness to make sure no loss due to electrolysis?
When searching for a surveyor what should I ask him regarding this issue?? What else does a surveyor do if aluminum vice fiberglass?? Thanks
jralbert
Site Admin
Posts: 885
Joined: Fri Jul 11, 2014 9:15 pm

Re: Aluminum in Salt water

Post by jralbert »

good move hiring a surveyor and good questions. Find one that has surveyed aluminum boats, of course. And share your concerns. Boat US insurance helped me find mine. Don't accept recommendation of seller or broker for obvious (conflict of interest) reasons. BTW: contract should read " subject to survey in case major problems arise. But if they do, you can negotiate based on findings. Expect wear and tear issues. God luck with your purchase and if it happens, good wishes for many years of happy boating. Marinettes, at least reasonably maintained, appear to have a very long life
-joel-
former owner 1988 '32 FB Sedan
Chesapeake Bay
twin 318 / 240 hp
Potomac MD
User avatar
Maestro
Aluminum Star
Posts: 175
Joined: Sat Jul 12, 2014 7:27 pm

Re: Aluminum in Salt water

Post by Maestro »

These are the ingredients of Trilux 33, pulled from the Interlux Website.

Note the second ingredient, Cuprous thiocyanate. It is a copper derivative. This stuff is considered safe for aluminum hulls IF you have a proper barrier coat in place. Cuprous oxide is the main antifouling agent in paint for non-aluminum boats. This is the bad stuff you don't want anywhere near your boat.

If you want 100% no copper products in your paint, consider products such as Interlux Micron CF, Sea Hawk Mission Bay, etc.

Xylene 0001330-20-7 25 - 50%
Cuprous thiocyanate 0001111-67-7 10 - 25%
Zinc oxide 0001314-13-2 10 - 25 %
Rosin 0008050-09-7 10 - 25 %
Zinc pyridinethione 0013463-41-7 2.5 - 10 %
Isopropylated triphenyl phosphate 0068937-41-7 1 - 2.5 %
Maestro
1986 32' Sedan
Chrysler 360s
1.5:1 Gears, 16x16 props

1970 28' Express
Single Chrysler 440
1:1 Gear, 14x12 prop

Green Bay, WI
User avatar
Busia
Royal Aluminum Star
Posts: 406
Joined: Tue Jul 15, 2014 12:21 am

Re: Aluminum in Salt water

Post by Busia »

Yes, I agree it works well (the Trilux 33) and they sell it for aluminum boats. But I am not going to rely on a barrier coat for separation. I sand blasted to bare metal and used a two part epoxy primer. Then two or three coats of zinc based E-Pro bottom paint. Not real happy with it but I feel it is safe. Sometimes I will add cayenne pepper to the paint, I think it helps. Just painted the bottom and used pepper this year, so I will have to pay attention to how clean it is when I pull it out
BUSIA
located in Ketchikan, Alaska. Gods country
32 foot Marinette (no fly bridge)
twin 350 Crusader (Chev 350) engines
1:1 Borg Warner velvet drive transmissions
Closed cooling (antifreeze in the engine)
Proud to be retired IBEW and an A+P
honestcharlie56
Royal Aluminum Star
Posts: 258
Joined: Tue Jul 19, 2016 8:27 pm
Location: Lake Charles, LA

Re: Aluminum in Salt water

Post by honestcharlie56 »

cayenne pepper?
1990 Marinette 32 Sedan Flybridge "Hubba" Lake Charles, LA
Twin Chrysler 318's
jralbert
Site Admin
Posts: 885
Joined: Fri Jul 11, 2014 9:15 pm

Re: Aluminum in Salt water

Post by jralbert »

Some swear by putting pepper in the mix to ward off critters. It could be an urban (marine) myth. But the one way to get a feeling is to put some of that on a piece of metal and on another piece, straight anti foul. Dunk them in the drink for a few weeks and compare. I did that with interlux 33 on one side and ZO No Foul on the other. Trilux won my unscientific but useful test. It was far less encrusted with barnacles.
-joel-
former owner 1988 '32 FB Sedan
Chesapeake Bay
twin 318 / 240 hp
Potomac MD
Post Reply