Hello, I am new here, nice to meet you! I have a question regarding adhesion to metal, and I would like to ask knowledgeable people of the automotive world, as I think you can help me out. I don't know if it can be considered off-topic, as it's more of a technical question, but would like to ask just in case. I am an fine arts oil painter. After lots of research and bad experiences with more traditional supports, I have decided to paint on aluminum panels. I am mostly driven towards using anodized aluminum panels or etch primed ones as supports for my paintings, but adhesion is indeed a concern, as I want to ensure the artwork to last long and not suffer delimitation along the way. Acording to an UK store, their anodized aluminum panels are unsealed and warrant a good absorbency and adhesion, even better if some 100 grit sanding is performed on the surface and a lead oil ground is applied on top of it before starting painting . On the other hand, I have read people advising to sand a raw aluminum panel and then etching it, still doubtful on how to proceed afterwards, if applying an oil ground also or just directly painting on top of the etching primer. These are my two main options, I would appreciate any advice or alternative on this topic. Thank you so much!
You're going to need zinc chromate for a primer. Worked for decades on airplanes finished painted with enamels.
Thank you for your reply. after applying that primer on top of the sanded aluminum, would it be good to apply a coat of lead oil ground (a traditional painting surface made of lead white, linseed oil and calcium carbonate), or better painting directly with fine arts oils would be good? I want the artworks to last for centuries, so I would try to avoid any coating that cannot last that long. I am aware yes. Currently aluminum is used in fine arts as a more archival support than canvas and wood, which are way more sensitive. What would you suggest as a better support? Remember I want to use it to create artworks that are going to be inside my and my clients' homes.
You do realize that you're dealing with people on this site who deal with automotive paints, acrylics, alkyds, and polyurethanes enamels not fine art oils?
I know, I wanted to ask people knowledgeable of working with metal, as the fine arts world is far from experienced with working on metal surfaces besides copper (which has already its flaws). I was curious if anyone knew about a similar issue.
Another thought , raw aluminum corrodes immediately , some sort of coating/ acid wash would be needed , especially on the rear of the painting .
Ordinary corrosion of aluminium forms a protective layer of aluminium oxide. Aluminium is unlikely to corrode progressively, especially in an indoor environment, especially on the back of the work, which doesn't get as much as touched for years on end. In fact anodization of aluminium is in effect a process of creating that protective oxide layer artificially and at a far greater speed. Anodizing is typically sealed by immersion in water at very high temperature, to dissolve the outer skin of oxide partially and have it reform as a smooth, tough surface. That rather suggests using non-anodized sheet and seasoning it, even outdoors, so that it can form a nice co**** layer of oxide, which will take either your primer/undercoat or your final paint directly far better than an anodized and sealed surface. I'd start with a highly thinned coat, which will soak into the oxide. Use a more volatile solvent to preserve the key.
Definitely the way to go. If not using an anodized panel, I see no other way of proceeding. Thank you so much for the thorough explanation, Ned. I was precisely asking about the anodized option due to that UK store's product. Their statement is that those panels are anodized, but not sealed, to warrant absorbency. Despite that, I am always doubtful on whether or not they are trying to sell their product and that's it, because no further explanation on how they are prepared is given, claiming the process to be ''registered and private''. Your suggestion is truly intriguing. Two questions: Can you expand a bit on the seasoning step? How should I proceed? And, after the surface has been finished, would it be sound to apply a lead oil ground? (lead white pigment, linseed oil and calcium carbonate), or could the lead cause any reaction with the aluminum? It shouldn't due to the oxidized layer, but I prefer to ask. The reason for using a lead white coat afterwards is to create a more homogeneous surface to paint on, as well as taking advantage of the lead, as its molecules strengthen the later oil painting layers.
As stated aluminum oxidizes immediately. Prep your part. When you're ready to shoot paint have it all mixed and in the gun. Scuff your part and wipe with panel prep, keep it wet, blow the panel prep dry and shoot paint immediately. Or Don't remove the Anodizing, it's bonded to the part. Scuff that without breaking thru and shoot paint on it.
Made these aluminum frame covers for the Model A twenty eight years ago. Asked the painter at the Freightliner shop we worked at, how to prep the aluminum for paint and what primer to use. He told me to wash it with soap and water until the water layed out flat without beading up... Did as he said, used a standard primer and painted with single stage paint. Still on there today and no problems...for what it's worth
2 words: epoxy primer. Sticks to just about everything, seals, and is water resistant. Sand the panels thoroughly (if anodized) with 400 grit, clean and shoot immediately. Lets sit a couple days, sand lightly with 600 grit paper, and paint away!
A good etch with a coat of epoxy after is indeed the safe bet. You're saying "ground" and we say base in this industry so I'll ***ume we mean the same thing. Your base needs to remain as thin as possible, or low mil thickness. Brushing oils are thick by nature and have their own delicacies over time and temperature changes so you want the 1st white lead base to be at the minimum possible thickness. Painting over anodized isn't as permanent as it seems. Just look under the anodize on used car trim. In 5 or more years that stuff is clouding up so it isn't the win/win it seems to be. Scuff the raw aluminum like @chopolds suggests, a light epoxy (preferably a non-sanding matl), and as light a lead based ground coat as you can get away with. Once dried you'll need to scuff that pretty fine too, no more co**** than 600 but I'd think 800 to 1000 grit would be best, then get your brushes out and have at it. Thickness of coatings will be what to watch. Keep it conservative, your brush work will be thick by nature anyway. How about some pictures? I'd like to see what you do.
As the OP stated ground is a specific product that oil painters use to cover canvases to provide a base so the oils don't absorb into the fibers of the canvas. It's like gesso for acrylic canvases. You do not sand it. It is based on Linseed oil. I doubt very highly it will stick well long term to epoxy primer.
We used to scuff chem-filmed panels at work to adhere metal and plastic mounting bases to them. Some we even made scuffing-templates for tight areas. After the item was bonded, the surrounding area was touched up with conformal coating to prevent oxidation. We had it in spray cans and little brush-on bottles. And of course a serious system for coating circuit boards.
The biggest detriment to long term adhesion is material thickness, or mil thickness. I'm guessing that even though centuries old fine art still exists it's that the canvas is a woven material that can microscopically stretch and shrink with the materials over the top. Maybe that's why even though the artwork is crackled and crazed it's still there, hasn't come off, and actually mechanically bonded. Maybe even a superior mechanical bond as the grounding layer has perhaps "stained" the canvas, soaked in, can't come off except where it may be excessive thickness or received some minor abuse. Frankly I don't see how fine art can stand the test of time on metal but the best chance will be the most ultimate of mechanical bonding. That requires both fine (etch) and co**** (sanding) preparation. In simple terms the coatings will move more or less than the platforms they're applied to. Our old endeavors on custom cars are crazed and cracked just decades later. Even old OEM lacquers cracked over time. How many heat cycles were involved? "But this is in a house..." and to that I say raise a rt hand and promise it will always be the same temp for, as stated above, centuries. And aluminum will move way more than steel. Every original paint aluminum bodied car I've ever seen is almost completely cracked or crazed. Steel fender finishes more intact, less of it. Is that a tell?
The second option is in fact what the UK store advices the clients to do. It sounded sound to me, but wanted to ascertain with other opinions, and also checking optional steps to improve adherence. Reading other comments here, it seems that just following the sanding + painting would be good, but not the best option out there, hmn. Definitely @chopolds and @theHIGHLANDER have a point here. I read before about etching, with lots of artists stating it wouldn't be necessary, which I am more doubtful of now I have read you all guys. An oil ground is not at all considered necessary to use as a base, my interest in it was the fact that the presence of lead could contribute holding and strengthening the top painting layers, but if it is going to struggle to adhere nicely to the support, that step could be skipped. Either way, if adherence is a problem with the ground, I ***ume oil paint would suffer from the same issue. Thankfully I am not too much into impasto (thick application of paint), so that contributes to the artwork's lifespan. I am adding a few of my last artworks, they all have thin painting application. You will understand why I am bothered about permanence: my art is pretty realistic and it pained me to see an old piece falling apart due to the canvas' expansions and contractions, being it the main reason of this whole interest in metallic supports. In fine arts, only copper has been used as a painting support in the XVII century. I read a lot about it, and seemingly copper and oil painting do bond not only mechanically but chemically, and there are copper panel paintings that have been around and kept a wonderful state to this day. What pushes me away from it are both its price and the fact some other paintings have suffered from deterioration due to the same oil-copper chemical interaction. I definitely agree the best chance should be to get the best possible mechanical bond between the painting and the metal. I don't know if it is possible or even worthwhile seeing the doubts the topic is raising here. Also the interest in aluminum is mainly how easy is to get these panels even in art stores around the globe, while steel is not at all considered in fine arts. Maybe considering ACM panels is another option. A lot of people paint on them after sanding, cleaning and applying an industrial bond primer on the polyester coating to use it as an adhesive to apply then the oil ground and paint on it. I have to admit that alternative sounds good as well, and adhesion tests seem possitive, but I am either way concerned on the long-term adhesion of industrial bond primers, and the lifespan of ACM panels, which have not been really created to serve this purpose. With all this options and opinions, I have to admit it to be hard to narrow down which would be the best alternative, other than experimenting and letting time test the different practices.
What about a synthetic linen or canvas type material? Organics like cotton, wool, hemp, etc, they can certainly deteriorate or suffer pestulance, yet so many fine works have indeed lasted centuries likely from being sealed in the paint mediums. Something synthetic as long as it wasn't soy based might hold up for many many generations. Just a thought, a possible alternative.
There exist in fact polyester canvases, which are used in restoration to be glued upon too deteriorated old canvas paintings. ACM panels are coated with a polyester material and apparently adhesion is so far considered good. Do you think that material could be better than metal? In fact, thinking about it, a polyester canvas nicely glued to a metallic support for more structural stability (like ACM, but maybe just a pure metal panel that could last longer) sounds quite the way to go. Could that be done, or glueing such canvas to metal would still be an issue?
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