Aluminum boat, JB Weld repair, now what to do???

[Luna Sea]

Moved the battery away from the transom of my Aluminum Lund and put in in a covered box. Used the JB Weld to repair the 6 holes that were forming where the deck meets the transom. (Left it in overnight in the rain and "Yikes"! Man, what a bunch of damage a battery can do!) Going to sand it down tonight. Looks like, whatever happened, the aluminum is no longer anodized(?) below where I made my repairs. Looks like something dripped down the back of the boat and removed all the coating. Is there something I can put on this one area? Clear? A wax maybe just to protect the bare aluminum? Or if someone can recommend a paint that won't react with aluminum in salt water, I'll paint this one little area. Thanks

 

[Boat_Boy!]

Re: Aluminum boat, JB Weld repair, now what to do???

It sounds like you have removed the anodization (or maybe just paint) from the aluminum. The absolute hardest thing you can put on aluminum is the oxide itself. Let me explain. There was probably some salts from your battery left on the boat when you hauled that battery out. The rain got in there, and solubilized the salt to create the acid (sulfuric acid in batteries). That etched the coating off of your boat. Now, if you leave it, the clean aluminum will begin to oxidize in the air, creating a hard coating only a few hundred microns thick, but harder than any paint you can get. it will not "progressively" oxidize.<br /><br />Aluminum oxide is so strong that it is used for polishing glass, making sandpaper etc. It needs to be carefully removed during welding of aluminum structures since the oxide melts at about 3200 degrees F and the aluminum itsleg melts between 1200 and 1400 degrees, depending on the alloy.<br /><br />My advice, leave it be. If you're putting that battery back there, get some rubbery deck paint, and pait the whole compartment.

 

[Luna Sea]

Re: Aluminum boat, JB Weld repair, now what to do???

Yeah, Boat Boy, thanks. Battery was on deck in back with no cover on it. One rainy night...........Got that solved though but when I sand down the JB Weld tonight I'm sure to remove some more of the anodized surface, well, I guess I could mask'n gring carefully, by hand. Sure looks ugly back there though. Like acid rain (no pun intended) ran down the transom. But I suppose it will blend in time? Kind of poked those areas this morning with a scraper, keeping an eye out for more.......... but you say it will get harder as it ages/oxidizes

 

[Boat_Boy!]

Re: Aluminum boat, JB Weld repair, now what to do???

Luna Sea,<br /><br />As that area gets a heavier coat of oxide on it, it will become, in chemical terms, stable... in fact, it's nearly inert. Aluminum oxide is tough stuff. Ask anyone who's tried to clean a badly oxidized aluminum hull or pontoon! All my compartments near the battery are coated with this rubbery deck coating. Go to your local Home Depot and ask for a filler for decks. I always try to tell them that I'm looking for something by explaining it's intended purpose, not necessarily what I wil be using it for. It's less confusing. Tell them you want to fill some large cracks or knots or something like that. Tell them you'll be putting a deck coating over top of the product. The stuff you want will be thick and grey in colour. I put mine on with a wide putty knife (3 to 4" wide). If you want, you can paint over the coating, mine was grey anyway, with the same colour as your boat. While a coating like this does not STOP the electrical conductivity you expereinced, it will insulate your boat from such events, making them less likely, and less devastating.

 

[Luna Sea]

Re: Aluminum boat, JB Weld repair, now what to do???

Thanks again Boat Boy. Happy with the dry battery box. Not sure I'll bother with this goopy stuff though. But made me think of putting a thick piece of rubber under the box.(?) Happy boating!