ACM prep?

I am wondering how others might be preparing ACM panels.  
The panels I use has a white coating in them.  Not sure what the coating is.  
I prep them by roughing the surface lightly with steel wool and then spraying a coat of automotive gray primer.  
I let that dry for a day and then I put a thin coat of Holbein oil ground that is mixed with umber and thinned with oderless turps to a mid tone (like what mark shows in his video). (I wear a mask and work outdoors when doing this).
I am wondering if others use a coated ACM and how you prep it.

Comments

  • GTO

    Wikipedia : the coating

    The aluminium sheets can be coated with polyvinylidene fluoride (PVDF), fluoropolymer resins (FEVE), or polyester paint. Aluminium can be painted in any kind of colour, and ACPs are produced in a wide range of metallic and non-metallic colours as well as patterns that imitate other materials, such as wood or marble.
    I have used sandpaper for tooth and xxx auto primer but the fumes were just too much.
    I switched to sandpaper and a tinted water based metal primer.
    Used sandpaper alone and painted direct to metal.

    Denis


  • @dencal. Did your ACM have a white coat of some kind on the aluminum?
  • GTO

    Some panels were coated (hardware store bought) others bare metal (art store bought), though they must have had some sort of transparent coating as aluminium will oxidise very quickly.

    Denis
  • I buy the ones with a white matt coating (which actually has a slight sheen) and then I use soft wire wool all over the surface. I then currently apply 2 coats of either clear or white gesso which I then sand lightly.

    I think the automotive primer will give you more of a bond, but from the articles I read by Golden on JustPaint.org it seems to be good enough as long as you give it time to dry/cure.
  • Thanks @dencal and @Richard_P sounds like gesso or enamel / auto primer will bond good to it.
  • I use much the same process as described above. I have the mat white panels that I lightly sand, then paint with the priming product below, which is the best painting surface I’ve found so far. My first paintings were on the bare aluminum art panels. I may have used the wrong sort of primer, as the paint surface is very fragile, and the paint is not bonded well at all. Live and learn. Or maybe bare aluminum is a terrible choice to paint on, which may explain why those particular panels are no longer available. 


  • edited September 8
    One of the reason I'm wary about primer is I once used several layers of Zinsser's Bulls Eye 1-2-3 - "100% acrylic resin water-based Interior / exterior stain blocking primer sealer." Which made a lovely surface, but it was super absorbent and made the oils 'dry' in hours even when thinned with walnut oil.

    I may have used too many layers but I prefer non-absorbent surfaces to increase the working time.
  • @roxy is the langridge primer lead based?  

  • @GTO it’s titanium white, and very thick - the instructions say to thin a bit before application. The downside of titanium is it takes ages (=weeks) to dry. I painted half a panel ages ago and just cut to size as required. At the rate I paint that’s no big deal, but might be a limitation to some. Paint just flows off the brush onto it, and I’ve not noticed any absorbency problems at all. In fact I first used it to fix some ‘pre-primed’ linen that, overnight, sucked the life out of any pigment applied. 
  • Hmmm interesting 🤔 @Roxy.  It takes about three days for the Holbein to dry, but I thin it way down.
  • If the coating is a plastic layer, as opposed to backed on enamel, then you can flame it just enough to haze the surface.  That is an oxide layer, and almost anything will stick to that resolutely.

    If you can find out what exactly it is, you may be lucky to find it is something they sell plumbing primer for like abs or pvc, that without the flaming will double adhesion.
  • Thanks @TamDeal.  I’m not sure what it is but since it can take enamel well it should be good with using an oil primer.
  • The coating is normally white coil coated polyester.
  • The primers for that sound pretty dire...

    Any the one SNAME member who has an approved test for SNAME, that I know, thecoatings test they use is just a scratch and masking tape test, it gives legit results and is easy to do if one wants to bother.
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