Alluminum Boat Repaint

[Wesc]

I am retoring an old 23' All weld aluminum boat.
any advise on how to get the old paint and scale out of the hull and off the exterior.

[gonzo]

Use an aircraft type remover. It is formulated to work on aluminum.

[Dutch Peter]

Can you have it sand/ice blasted?

[Wesc]

I was thinking about sand blasting but didn't know how it might effect the integrety of the aluminum. erosion?

[gonzo]

Ice blasted?! How does that work?

[Dutch Peter]

Gonzo,

Ice blasting works the same way as sand blasting. Don't ask me the particulars of the machine, but essentially water is frozen into small ice balls and released under high pressure. The advantage is that less dust is formed, so less of a health issue!

[Dutch Peter]

I was thinking about sand blasting but didn't know how it might effect the integrety of the aluminum. erosion?
The blaster can adjust the pressure of the equipment in order to just skim the surface and remove the paint. You'll loose the oxide skin of the aluminium, but that is back in a couple of hours/days.
It shouldn't be a problem.

[Paul Mooney]

sandblasting produces the best "tooth" as well as does a great job cleaning the oxide off, Take care to be sure the surface is grease oil free first. Check out Meta in France at http://www.reducostall.com/ they have been building aluminum yachts for 25 plus years. Their standard spec is sandblast and coat with "Inversalu" a zinc primer. They use this as a antifouling coating in mid to northern lattitudes. Below DWL gets 3 to 4 coats, topside get one coat Inversalu followed by epoxy followed by topcoats. Also see our paint spec at www.fairmetalboats.com we use the same spec now for steel or aluminum based on Meta's very successful corrosion control and coating life using zinc on aluminum.

[Richard Petersen]

The ice blaster sounds like a poorly adjusted snow making machine. :p

[Arrowmarine]

I agree with all above replys, but keep something in mind. A quick call to my brother, head painter at Alumaweld Boats, confirmed a couple things. If you are using a "zolatone" type paint inside, all you need to do is make sure to remove any loose paint(which he said can be done at your local car wash with a pressure washer held about six inches away from the surface) then reprime and shoot the zolo right over the top of the old paint. He says the old paint(as long as it is securley adheased to the metal, actually give a better bond than clean aluminum. The outside can be done in the same fashion, just add body filler to any low areas and respray right over the top. This has been done on many a repair boat in his, and my own experience(I fix em, he paints em:-) and no returns to this day.
REMEMBER THO, He does say the "right" way is to strip and clean all paint from the boat and start fresh. The above is meant to save a little time and money if so desired. Just depends on what you are trying to achieve with your finished product. ( Incidentaly, we have had great success with the soda blasting technique)
Hope this helps, Joey

[MATTRESS GUY]

Soda Blasting Is The Best , Less Sensitive, More Adjustable, And Less Messy, You Just Wash It When Your Done...soda , Just Like Baking Soda...i Dont Know All The Detailes But I Think Its Great!!!

[Wesc]

Thanks for all the advise. I think what I am going to do is use a mixture aircraft stripper, Staneless wire brushes & high presure washer. All of wich I have readly avalible.

I have another question. When I removed the wood deck I discoverd many broken welds where the crossmembers atach to the hull. I have the equipment and have welded alluminum before but have never welded on the hull of a boat.

Any advice.

The boat is A 23FT 1984 ALWELD V Hull. I use a Miller 210 with a spoolmate.

[Richard Petersen]

Clean aluminum = clean and pretty weld. Make a few passes on the underside of a support where it will not be seen to get your settings. :)

[gonzo]

Use a proper aluminum alloy wire. Your supplier should know.

[Arrowmarine]

Use 5356 alloy wire and clean your joints with a wire wheel. 210/ spoolmate is sufficient. Just practice a little first.

[Arrowmarine]

Little more advice: If you use a pressure washer, take an air nozzle and thoroughly blow out the areas that you are going to weld to make sure that there is no water in them(I always blow out my seams again the instant before I start welding just to make sure). Water will contaminate and make you weld worthless. Also, dont worry about it just because it is a boat hull. It's no different than welding anything else. If you burn thru, sand off any excess and use a air nozzle on one side and soapy water on the other to check for leaks. If you have a leak, clean all water and soap off(again, with the nozzle) and weld and sand again. Reapeat untill you got it. Believe me, even seasoned vets(myself included) have chased leaks and holes over several "fill and sand" cycles. Especially on old hulls that have a lot of contamination. For a used hull, the important part is clean, clean, clean!!! You will get a lot less porosity and a better flow of your weld. That means fewer chance of failures. If your not happy with your weld, grind it out, clean it up and try again:-) If I can provide anymore help, let me know.
Peace, Joey

[Arrowmarine]

One more thing. If you sandblast, you still have to clean your joints with a wire wheel or small sander to eliminate the loose "sandy surface" of the aluminum that is left by the sandblasting. This stuff kinda makes your welds a little dirty and can cause porosity.(anyone who has welded a cast aluminum piece without dressing it up a little can testify to this). It's quick and easy and it will up your weld quality some.
Joey