Paint prep for aluminum boat

[wh500special]

You guys seem to have such a wide breadth of knowledge I thought I'd ask thi question on this forum...

I'd like to freshen up the exterior paint on a 20 year old Lund boat. It's spent it's entire life outside and largely in the water since it previously was a rental boat at a lake in northern Minnesota. Lund used a pretty good paint on these, so what wasn't rubbed off by the docks, rocks, and whatnot is in pretty good shape.

Aluminum is hard to stick to, long-term. So leaving what I can of the factory finish is probably a good idea. So the plan is to scuff things up, feather what I can, wipe down, and prime with zinc chromate primer. Then, paint with urethane.

Anyway, I have been hand scuffing this thing with scotchbrite pads and it seems to really be just the ticket. I'd like to use a random orbit sander with the same type of pad to speed things up. There are tons of rivets on a Lund, so sanding with normal sandpaper and pads on a ro is cumbersome at best.

The scotchbrite pads are quite pricey...so I don't want to head down that path if it's a dumb idea.

So, what am I asking?

1. Does this seem a reasonable approach?
2. Anybody ever use the scotchbrite pads on a ro sander?

Stripping the paint completely is an option, but not what I'd like to do. This is a fishing boat, so I'm not looking for a concours finish. But the thing looks really bad as it sits.

Thanks for any suggestions,
Steve

[terrydowning]

FWIW
I think you're headed down the right path.

I have used scotch brite pads under a palm sander but not an RO, It worked great for me.

If you're not concerned with brand, try the 99 cent or dollar tree for the pads. I picked up a pack of 6 green pads for scuffing and such for 99 cents.

I don't know the grit, but they were green and felt about the same as the scotch brite pads. They work great for removing rust and I don't feel bad disposing of them when worn out.

Pics of progress and completion of course.

Best of luck.

[tenbears]

Festool calls them viles, they come in both 5 and 6 inch hook and loop backs for their disc orbital sanders. 3m makes hook and loop scotchbrite pads but I've only seen them in 4-1/2, 8 and 10" at the welding shops. Use these heavy duty ones on right angle grinders for polishing, Yep Aluminum. That is the easy part. The preferred approach is to use an acid etch primer paint which is nasty, but Zinc chromate works for awhile anyway. After that any high quality single part marine polyurethane paint works. For an even better long lasting finish use a two part poly like Awlgrip. Best to spray and a good 4 stage HVLP sprayer will lay down and excellent finish. You can roll and tip but I always end up with sags using the roll and tip.

[dforeman]

I have a LOWE 16' Canoe that I painted a few years ago. Orriginally it was never painted. It was a used canoe from a Boy Scout Camp that closed down a few years back and just kind of had that clear type finish they hit it with during construction. I scuffed it up with a scotch bright pad, primed with Zinc Cromate Primer and painted with camo paint you pick up at the marine supply outlets. That was over 12 years ago and so far it has held up well. Like you mentioned, don't worry about getting all the old finish off. You just want to scuff up the old finish, remove any loose spots and oxidation you might see. The Zinc Cromate Primer will do the rest (it is fairly tuff stuff). But, make sure you coat anything that needs painting with the Zinc Cromate. Around the rivets, you also need to just scuff. They don't have to be perfect though. Just enough for the Zinc Cromate to adhere.

Ooooo And, be weary that the Zinc Cromate does set up fairly quickly. I did my canoe by hand, so what I did was just pour out a little bit at a time into another container (just enough so I could get it applied before it started to set up). I also did the painting outside. The Zinc Cromate puts out a lot of fumes that you probably don't want to be inhaling any more than necessary.

[lightnin]

First is it riveted or welded?

If it's riveted together that's a big source for leaks in old aluminum boats.
Especially rental boats they get used more and abused more than most boats.
You might want to go to bare metal around all rivets below the water line
then spread and smooth some JB weld around the rivets inside and out before painting.

What kind of paint job are you wanting to do?
Solid color, Camo, Other?

[wh500special]

Thanks Guys.

Progress will be slow; if for no other reason that it takes me an eternity to get a project moving.

It's a riveted hull. Lund really believes in rivets and sinks them everywhere. So in addition to having them on seams, they're also holding the seats in place, the spray rails on, etc. That's the primary difficulty in using normal sandpaper since it doesn't have the flexibility to float over a rivet like scotchbrite. It tries to grind 'em off.

The boat is surprisinly water tight for having so much use. A testament to Lund really knowing what they're doing. But I do have a leak "somewhere" that I haven't found yet that should be in an unpainted portion of the hull as Lund doesn't paint the bottoms in this boat class.

I plan to go with the standard red color that this boat originally was painted. The title says "red", and I like it. I gave up duck hunting years ago, so don't need the camo treatment. Glossy red won't have the sin-hiding power of dull OD green or brown, but I'm not too particular.

Thanks for the Festool Vlies suggestion. I wasn't aware of that series of abrasive and it looks to be exactly what I want. In some freak oversight, the Festool abrasive "Vlies" is actually less expensive than the scotchbrite hook and loop 5" discs. Go figure. I'm ordering some later today. I happen to have an RO125 Festool sander, so I'm set. Craigslist bargain that was "supposed" to be a sell-it-on-ebay-and-make-a-profit deal, but I really like it....

Thanks for the suggestions!

Steve