Painting aluminum

[REBrueckner]

"...Stainless steel screws in aluminum parts are a disaster..."

Isn't that just the mix in my Hatteras aluminum rub rails? I'm quite sure the through bolts are SS and I can't see any deterioriation between them and the aluminum rub rail. Whatever mix Hatteras used, it sure APPEARS stable.

Is this a common problem in window frames? The few pits I see in mine don't seem to be associated with screws. Would the window frames and rub rails be a different aluminum composition?

There are clearly irregularities from aluminum piece to aluminum piece, some are bright and some are dull, and the anodizing is hardly uniform within a given piece after many years with some pitting here and there.

 

[Paul45c]

The stainless/alum prob is a well-known one over the years; the only thing that helps is to keep the two metals as isolated from each other as possible. Apart from mechanical spacing (like the nylon washers Rupp puts between its outrigger couplings of stainless/alum), the best thing I've seen used is a product called TefGel -- it's specifically made to slow the process of galvanic corrosion. Nothing will work forever, but TG will last a long time. Great stuff.

 

[dwaynec]

I sanded my rails with 220 grit until I had sanded the anodizing off. I could tell by the color difference when I was down to the bare aluminum. I then used 320 grit to smooth out the scratches left by the 220. Then I polished with the Flitz using a 7" buffer.

As I stated before, my rails still look pretty good after about 6 months exposure to the sun and rain and .... During the summer season my boat is in an uncovered slip where the sun can beat on it all day long. During the winter season we are in a covered slip. Since we boat in "fresh" water we don't have to deal with the effects of salt, so that may be the reason that the rails still look pretty good.

If I were going to do this again, I would not have stopped with the 320 grit. I would take it down to either 400 or 600. I say that because in places I have had to hand sand to get rid of some of the scratches. I will also say that I would not do this unless the boat was being repainted, as ours was.

Using the Flitz with a power buffer will load up the buffer pad really fast as you don't let the Flitz dry. I would typically get about 30ft of rail done before the pad was so loaded that it was ineffective. I also used a plastic tarp taped above and below the rail to keep the Flitz from being slung all over the boat from the buffer.

By the way, Flitz is great for cleaning and polishing the paint too. When you are done it has that "wet" look that we all desire.

Hope this helps....

 

[exsailor]

Thanks for the feedback on the aluminum pulpit. after waiting forever for Cameron from Hatteras to call me back (No longer works there?) I talked to Allen Hills and he told me that most were built with fiberglass, but some with none. However Cliff from Ideal says they made several for the Hatteras factory, so who knows. I was just surprised to look at a 53ED 1984 that had one.
exsailor

 

[Boss Lady]

The problem with aluminum is that is if it were not for the fact that it corrodes very quickly it would not exist at all, what I mean by that is that it forms a protective oxide layer when exposed to oxygen and stops corroding. when we buff or polish it we remove this protective oxide layer and the corrosion starts again. Any type of corrosive (salt) greatly accelerates this process and prevents the protective layer from forming, and we wind up with the white chaulk remnants of the aluminum. The only thing that stands a chance is the anodizing process and that evenually goes to hell. I have several powder coated items on my other boat and they have already started bubbling up under the paint. You can maintain aluminum but it takes a lot of time to clean it, and apply a protective wax or coating, if you get behind, mother nature wins and it looks like crap. Anodizing is the best (about 10 years max, usually less, from my experience) if you paint, just be prepared to do spot painting because it will corrode again. If you do paint, I would recommend a zinc chromate primer to slow down the corrosion.

 

[GaryNW]

When fasteners are needed in aluminum boats, they are stainless. Titanium would be better-but hey these aren't airplanes ($$$$$). High end gillnetters in the PNW and Alaska are aluminum. Fasteners are generally not needed below the waterline because struts, logs and such are weldments. You can't avoid fasteners above the deck with all the stuff you have to mount. I believe you would find that steel and iron parts (like hyd blocks) are isolated with gaskets or even wood and fastened with stainless. BTW, aluminum commercial fishing boats aren't expected to look like yachts- the shiny is gone in about a year.

Hard anodize-unpainted- is used on aircraft where no paint scheme will hold up. Cockpit window frames and fixed wing and stabilizer leading edges are examples. This anodize is kind of a gun metal grey. Such treatment would best all but concrete or steel pilings. But.....

By the time you spend the money to get the best damned aluminum rub rails in the world, why not just go stainless?
Gary