Painting exposed aluminum tubes on an ultralight - which paint?

Discussion in 'Finishing Techniques' started by skwier, Sep 15, 2018.

Help Support HomeBuiltAirplanes Forum by donating:

  1. Sep 15, 2018 #1

    skwier

    skwier

    skwier

    Active Member

    Joined:
    Jul 28, 2015
    Messages:
    39
    Likes Received:
    10
    Location:
    Colorado, 5400 feet
    Purely for appearance I am thinking of painting exposed aluminum tubes on a ultralight a pale golden yellow. To save weight I suppose spraying would be best. What paint would be best? Will any paint stick to exterior aluminum for long? Do the "paint plus primer in one coat" products add any value?
     
  2. Sep 15, 2018 #2

    blane.c

    blane.c

    blane.c

    Well-Known Member

    Joined:
    Jun 27, 2015
    Messages:
    2,819
    Likes Received:
    476
    Location:
    capital district NY
    You have to conversion coat the aluminum first, this removes the non bonded oxide layer on the surface of the aluminum and replaces it with something that is bonded to the aluminum. Then you can paint that.
     
    MadRocketScientist likes this.
  3. Sep 15, 2018 #3

    Dan Thomas

    Dan Thomas

    Dan Thomas

    Well-Known Member

    Joined:
    Sep 18, 2008
    Messages:
    4,682
    Likes Received:
    1,917
    Never tried ther paint-plus-primer stuff, but painted a lot of aluminum. Paint on aluminum as it sits has a life measured in minutes, almost. Aluminum forms a skin of oxide that offers little "tooth" for bonding. (Oxides are often created by some types of cutting fluids, and the oxide acts as a super-slippery lubricant in machine work.) That oxide needs to be removed, usually by acid-etching, and to futher protect the metal it is then treated with alodine to form an impermeable barrier to oxygen. The acid leaves microscopic pits in the metal for the primer to mechanically bond to. The paint bonds to the primer. Zinc chromate is the usual primer for aluminum, as the zinc will act as a sacrifical element to preserve the aluminum.

    Yellow? Excellent choice. All other colors are wannabes. But today's yellows are nearly transparent because they no longer use lead in the pigments. Paint the surface white first, and the yellow will be brighter and you'll use less of it.
     
    akwrencher likes this.
  4. Sep 15, 2018 #4

    TFF

    TFF

    TFF

    Well-Known Member

    Joined:
    Apr 28, 2010
    Messages:
    11,007
    Likes Received:
    2,966
    Location:
    Memphis, TN
    Mist some spray can self etching primer on and do the same with the paint. If it's more than a cover dusting, you are putting too much on. If it looks really pretty, it has too much paint on.
     
  5. Sep 15, 2018 #5

    Aerowerx

    Aerowerx

    Aerowerx

    Well-Known Member

    Joined:
    Dec 1, 2011
    Messages:
    4,527
    Likes Received:
    1,198
    Location:
    Marion, Ohio
  6. Sep 15, 2018 #6

    pictsidhe

    pictsidhe

    pictsidhe

    Well-Known Member

    Joined:
    Jul 15, 2014
    Messages:
    5,585
    Likes Received:
    1,422
    Location:
    North Carolina
    'Pretty' anodising seriously reduces the fatigue life of Al.
     
  7. Sep 15, 2018 #7

    skwier

    skwier

    skwier

    Active Member

    Joined:
    Jul 28, 2015
    Messages:
    39
    Likes Received:
    10
    Location:
    Colorado, 5400 feet
    Thanks Dan. With these key concepts I can find what is needed.
    This is the kind of clear and detailed help that is the best of the HB forum.
     
  8. Sep 16, 2018 #8

    Daleandee

    Daleandee

    Daleandee

    Well-Known Member

    Joined:
    Sep 11, 2015
    Messages:
    810
    Likes Received:
    494
    Location:
    SC
    Joe Fisher likes this.

Share This Page

arrow_white