Can Aluminum be painted?

Discussion in 'Metal Boat Building' started by jdworld, Mar 4, 2010.

  1. u4ea32
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    u4ea32 Senior Member

    Its been a long time -- 35 years now. But way back then, I was sailing master on an aluminum maxi ketch, built at Abeking and Rassmussen. When the second owner bought the boat, there were several places where the paint was bubbling above the waterline, and pitting below the waterline. We got a big crew of guys to hand sand all these places, and we applied zinc chromate (I think -- it was yellow) primer that was specifically for aluminum. Then lightly sanded the yellow to make it smooth, and then painted over with bottom paint or topside paint (not 2 part, I think it was just enamel, like car paint). We applied all the primer and paint with brushes. Worked great. Very high gloss topsides. Easy to spot repair. We used no acid or alodyne.
     
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  2. CDN-CUCV
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    CDN-CUCV Junior Member

    I wonder if a prepping the aluminum with chromium oxide prior to welding would expedite the process? Then a post-treatment of the welded joints?

    Any thoughts?
     
  3. Ike
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    Ike Senior Member

    When I was on a CG ship that had aluminum superstructue we first removed all the paint (wire brush, sanding etc.) then clean it with plain old soap and water. Then we applied an etching solution we called Blue Death. I have no idea what was in it but we used rubber gloves. You didn't want to get it on your skin. Then we applied zinc chromate (it was a nice yellow) and then painted.


    I don't know if chromium oxide would work. Any aluminum guys out there?

    I found this on a page about prepping aluminum "IN PROCESSING ALUMINUM, OXIDES AND SMUTS REQUIRE AN ACID DEOXIDIZING
    BATH THAT WILL COMPLETELY REMOVE THESE SOILS." http://www.stoodyind.com/Catalogs/FISC/current/05catpg468.pdf Of course keep in mind they are trying to sell their product. But I think they are right. Something is required to remove any dirt, oils or any other contaminants.
     
  4. kmorin
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    kmorin Senior Member

    Allodyne is Zinc Chromate give Chromium Oxide

    Ike,
    the yellow stuff was a chrome solution on the acid 'blue' that cleaned the aluminum oxide and then allowed the zinc chromate solution to substitute chrome in the oxide formation on the cleaned or 'deoxidized' aluminum.

    In other words: Your experience is exactly as posted above- but you may not have looked closely at the chemical contents and bonds formed- but they're set out in this topic.

    etch; convert to chromium oxide while wet; let dry; add primer; then topcoats = painting aluminum.

    Cheers,
    Kevin Morin
     
  5. Ike
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    Ike Senior Member

    Thanks Kevin. I might also add it's clouded by almost over thirty years. It was a long time ago . Senior moments get more frequent. LOL
     
  6. Bigfoot1
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    Bigfoot1 Junior Member

    look on the Interlux or awlgrip website and down load the paint instructions.
    Awlgrip is good, pricey, Interlux is as good, still expensive but will last
     
  7. CDN-CUCV
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    CDN-CUCV Junior Member

    I like the Awlgrip paint, can't beat the finish, but like you said, pricey. We sprayed it at Canoe Cove when I was there years ago.
     
  8. espresso
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    espresso Junior Member

    Blast, Alodine, then paint anyone?

    Hi,
    If I had to blast my 5083 Aluminium hull with garnet, and then within say 20 minutes wash it off with Alodyne, would this be O.K.?
    Basically, how long before the Aluminium Oxide film starts to re-form?
     
  9. CDK
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    CDK retired engineer

    The oxide layer starts forming immediately when air is present. That is the very reason why you cannot solder it, no matter how short the time is between sanding or brushing and the attempt to solder.
     
  10. Bigfoot1
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    Bigfoot1 Junior Member

    aluminum painting

    Re blasting aluminum,
    I would stay away from blasting aluminum unless that it is very thick plate, 1/4 inch or larger. It is not necessary as the oxide that forms on aluminum is thin. Ie you are not trying to remove mill scale.
    We have built many aluminum boats over the years and we would sand it, then use an acid etch prep, then prime it. As per the paint manufacturers recommendation.
    Also, if you sand blast thin sheet, you can actually warp the sheet.

    The easiest thing is to just follow the paint manufacturers processes
    It would go something like this
    wipe the boat with an solvent, ( by solvent, something like laquer thinner, toluene, of course these products need to be handled safely, I mean a product that dissolves oil as compared to a diluent that just thins the oil, like varsol,wd 40 etc) Many paint manufactureres use a water base oil wash
    Then use a wash like alodine
    then an acid etch primer,
    then the surface coats


    To CDK
    Yes you can solder aluminum, but not with ordinary solder.
    Sand the material, use a flux to cover then solder.
    At a material show many years ago, there was a person doing this and
    until that time, I also did not know that you could do it.
    I have seen an experienced welder oxyacetylene weld aluminum though with the aluminum oxide melting at a higher temp than the aluminum substrate, it was tricky. He used a carburizing flame, ie blacker flame, ie a flame short of oxygen, and would wipe the aluminum wire into the joint. This was make shift as he did not have tig or mig aluminum capability on hand. Similar to oxy welding lead.
     
  11. CDK
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    CDK retired engineer

    Yes Bigfoot1, in an inert atmosphere you can both solder and weld.

    Although...... I Have a small jar with a skull and bones printed on the lid and the text that it contains a flux for soldering aluminum. Bought it at a show many years ago, but never succeeded in soldering a wire to an aluminum heat sink.
    And at the time I saw the guy do just that!
     
  12. WickedGood

    WickedGood Guest

    JD World

    How big is your boat?

    I bought 4 gallons of Tri Lux for my 44 ft Winninghoff and only used 3 and 1/4 gallons. I sold the boat and dont need the Alum paint anymore.

    It is around $240 per Gallon at Hamiltons in Portland, Maine

    Im right down the road in Saco, Maine and could sell you the 3/4 Gallon for $100 Cash


    The Paint is Blue. Like it should be.


    Capt Walt

    WickedGoodOutdoors@Maine.rr.com


    PS: What do you want to Solder to Alum? You can make a paste of Borax to braze.

    I also have a TIG Welder and maybe could do a small job for you if you buy the flux wire & Gas.
     
  13. alidesigner
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    alidesigner Senior Member

    For simple alloy repairs this stuff looks good. I havent used it so cant say how good it really is but have seen a similar product demo'd at a car show and have just ordered some to repair an alloy bonnet on a car I am restoring.

    http://tinyurl.com/alloywelding
     
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  14. keysdisease
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    keysdisease Senior Member

    Yes,

    Choose a well regarded marine paint manufacturer and follow their directions for painting aluminum.

    Anything else you do at your own risk for failure, and a failed paint job is a nightmare to fix.

    Steve
     

  15. WickedGood

    WickedGood Guest

     
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