Pitted aluminum hull

[Ted Wells]

What causes "pitting" on aluminum hulls? Can it be prevented? Yes, the boat is used in salt. How do I fill the pin holes and can I prevent further damage?

 

[PurpleDragon]

Re: Pitted aluminum hull

Ted,<br /><br />As far as I can tell, the pitting would probably be a minute electrical reaction between the aluminum hull, and the electrolytes in the water - causing oxidation and pitting of the aluminum.<br /><br />The only thing that I've found in a repair manual on the oxidation, says to lightly sand the white powdery oxidation off, but unfortunately, the text did not offer suggestions with what you could fill the pinholes with.<br /><br />Depending on the condition of the boat, you might be able to just use a clear silicon outdoor (waterproof) caulk. Wear a ruber glove and smear it into the inside, and outside of the pinholes. Let it cure thoroughly, and you should be pinhole free.<br /><br />G'Luck!<br /><br />Rex

 

[petryshyn]

Re: Pitted aluminum hull

Hi Ted<br /> Don't know much about corrosion, as we don't get much around here, but I'd bet there's an electrode made just for that purpose.(sacraficial anode = zinc)<br /><br />Might want to be careful on the silicone you choose if you go with Rex's method. Most use a acid base for curing and will cause more corrosion in time. Be sure its metal safe.<br /> <br /> Pending on how 'big' the pitts are, you could try spraying the boat with a 2 part aluminum primer, then top coat with a 2 part plastic paint. Pending on who's product you use, be sure to follow their preping procedures. <br /> I've used a "spray bondo" on vehicles. It may work if holes are large, as it gives quite a build up. Again, it must be top coated.<br /> But don't forget......preping of the metal is everything! If you wimp out on the prep, it'll haunt you....<br /><br /> All these chemicals are highly toxic. Be sure to follow manufacturers recommendations for safety!!! Or better yet, get it done by a professional.<br /><br />(my .01 cent worth)<br /><br />Careful and Good luck

 

[Mike M2]

Re: Pitted aluminum hull

If you paint the hull with a bottom paint, you must use a special paint designed just for aluminum. If you use regular bottom paint, it will pit all the way thru, i've seen it on pontoon boats. The aluminum bottom paint is far more toxic then regular bottom paint, and is illegal in Canada, where they use another type of paint thats $40 a quart! When we have pitts all the way thru, we weld them closed. Aluminum welding is a little pricey, but i think it's the best way. If they are not thru, i've filled them with liquid metal type products.

 

[SeaDawg]

Re: Pitted aluminum hull

Ted, I agree with the guys above, but here is a true story.<br /><br />I gave a 12 ft. aluminum boat to my neighbor a few years back, that another guy had given to me, because he had let his pen raised quail nest in it and the quail doo doo ate hundreds of holes in the bottom of the boat, some as large as 1/4/ inch.<br /><br />My neighbor bought a gallon of auto bondo, and roll of auto fiberglass mesh, and he used vinegar to clean the hull very good. He patched it up, and has used it in a nearby lake for several years, and it has held up fine. He painted it with oil based enamel. Nothing has cracked either.<br /><br />Granted, he only uses a trolling motor, but he's happy.<br /><br />Not very scientific, but it worked.

 

[Mike M2]

Re: Pitted aluminum hull

Great idea! coat it with glass!

 

[turtle1173]

Re: Pitted aluminum hull

Ted,<br /><br /> I have a 1972 starcraft and we used it a lot in saltwater when I lived in the Bay Area (CA). It was never left in the water, it was always trailered. I started having a lot of problems with leaking and took it in to have it looked at. I was told the the hull was "pitted" and that is was most likely caused from use in saltwater. There suggestion was to have the bottom of the boat fiberglassed. That is what I did. It was expensive ($700) but I never had anymore problems with leaks.<br /><br />Shane

 

[SCO]

Re: Pitted aluminum hull

I have a book on corrosion, and looked it up. <br />It indicates that pitting is a stagnant water phenom because ions build up around each pit creating a mini electrical current from the center of the pit to the perimeter. When you are running those ion's can't build up. Its happening in the driveway or boat stall.I just got an aluminum boat. Thanks for putting me on to the problem.