Register now to get rid of these ads!

QUESTION: Painting an ALUMINUM RADIATOR?? Cooling efficiency???

Discussion in 'The Hokey Ass Message Board' started by KIRK!, Dec 28, 2006.

  1. KIRK!
    Joined: Feb 20, 2002
    Posts: 12,031


    Is there a definitive answer on how much painting an aluminum radiator lessens it's cooling efficiency? I like the idea of a thinner radiator but I don't want to look at it.

  2. Muttley
    Joined: Nov 30, 2003
    Posts: 18,444


  3. KIRK!
    Joined: Feb 20, 2002
    Posts: 12,031


    "...sprays on thick enough to cover completely, yet thin enough to not interfere with heat transfer."

    That pretty much answers the question. Thanks Muttley!
  4. alaskanroadzombies
    Joined: Oct 10, 2006
    Posts: 72


    used to paint my radiator in my stock car. since we werent supposed to run aluminum radiators. never had any trouble with it.

  5. fab32
    Joined: May 14, 2002
    Posts: 13,985

    Member Emeritus

    A thin coat of BBQ black works well. Available at most hardware stores for outdoor grills. If the radiater is new it will stick well and last. Only use enough to get an even color. Applied this way it will actually enhance heat transfer.

    kidcampbell71 likes this.
  6. Yeah, I remember hearing somewhere in a physics class or somewhere that black is the best color for radiating heat. They often anodize heat sinks in electronics stuff black. A lot of Formula 1 type race cars have black engines, black valve covers, etc. I guess the secret is just making sure the paint isn't too thick. Aluminum conducts heat well, but paint doesn't.

    The last time I painted a radiator, I remember hitting it from two angles, rather than straight into it. I just dusted it on until it looked black. By hitting it from an angle, it only gets paint on like the first 1/4" or so of the fins, but not any in deep inside the fins. It makes it easier to get it a uniform black color without having to cake on tons of paint. I can't remember what brand it was, but it was some kind of dull black epoxy paint made specifically for radiators.
  7. 1320stang
    Joined: Nov 21, 2006
    Posts: 166

    from Edmond, OK

    Yeah, you could anodize it, never heard of anyone doing this, but you wouldn't have to deal with chipping paint.
  8. HotRodFreak
    Joined: Mar 25, 2005
    Posts: 1,935


    Any cheap black paint will increase heat dissapation, also for engine blocks. That is why engine builders and radiator shops use black.

    Maybe someone out there can offer their opinion.
    This is AMERICA!
  9. Eagletucky
    Joined: Feb 21, 2005
    Posts: 728


    My Bro in law works for an outfit that fabricates radiators for NASCAR, IRL, etc. He told me they have run tests before and found that radiators painted black are slightly more efficient than if left in bare aluminum.

    They know their shit.....I would believe him.

  10. dragrcr50
    Joined: Jul 25, 2005
    Posts: 3,865


    on the gold 55 gasser we used john deere blitz black paint on it and it cools great...
  11. 47bob
    Joined: Oct 28, 2005
    Posts: 625


    When painting aluminum most people prime the surface bacause paint doesnt like to stick to it but DON'T use zink chromate on a radiator as it will hold the heat in. Don't ask me how I know. .....Bob
  12. Yeah, that's true, paint doesn't stick worth a crap to aluminum usually. I had pretty good luck with some stuff called "Bulldog Adhesion Promoter" getting paint to stick to aluminum. It's clear and really sticky. It comes in a spray can. I don't know how well it conducts heat though.
  13. old kid
    Joined: Mar 21, 2005
    Posts: 826

    old kid
    Member Emeritus
    from middle ga

    i've painted several aluminum radiators satin black with no heating problems.
  14. All the radiators I put in the old corvettes I restore are aluminum and they are all painted.
  15. Crease
    Joined: May 7, 2002
    Posts: 2,878


    I am digging waaaay back here, but I don't think the color really matters in this case. It is true that black would absorb heat and a shinier surface would reflect it. If this is a closed hood car, this may come into play somewhat. I am guessing that the really problem would be the insulating proerties of the paint. These properties would vary from paint to paint. However, I doubt that any change in efficiency would be noticable. I took like 3 semesters of this stuff and now I can't remember crap, oh well.
  16. GooGooMuck
    Joined: Nov 20, 2005
    Posts: 50

    from Tacoma, WA

    If you're really serious about a stock appearance you could look in to Swain Technologies "stealth coat" it's designed for intercoolers and such but it actually increases thermal efficiency (it's a street racer secret) and is flat black.
  17. raffman
    Joined: Sep 28, 2005
    Posts: 658


    I have been giving this subject some thought myself, an aluminum radiator in a 34 looks too "street rod". I want to paint my Afco unit but know the adhesion problems. Black epoxy will adhere but doesn't hold up well to uv. Could shoot black urathane over that but too much film thickness might interfere with cooling. I guess the answer is to go that route but keep it to a minumin thickness. Does anyone remember the tests that one of the mags, maybe HotRod did a bunch of years back on colors and heat transfere? Seems that the color of surounding area was just as important , dark vs light.
  18. I got curious about this subject and found this physics lecture:

    The main point of it is that things that are good absorbers of light or heat energy are also good emitters of light or heat energy. So black surfaces absorb the most heat of any color and they also emit the most heat of any color.

    So yeah, it does make sense that a black radiator is going to emit more heat than a shiny aluminum one, as long as it's not caked on super thick to where the paint acts like an insulator.

    I think most of the heat is transferred to the air as a heat exchanger, but some of it is radiated out in all directions as infra red light. For the heat that shoots out in all directions from the radiator as infra red light, it would make sense that you don't want to surround your radiator with shiny aluminum or chrome or bright colored paint, because those bright colored things would just reflect heat back towards the radiator again.

    So in a car with a grill mounted in front of the radiator, I think it could possibly make the radiator slightly more efficient if you painted the backside of the grill with black paint too (or don't even have a grill).

    But I think the vast majority of the heat exits by warming the air passing through the fins of the radiator. Painting the radiator black probably just makes it slightly more efficient.
    Stogy likes this.
  19. bogart62
    Joined: Dec 20, 2006
    Posts: 187


    Lood in the Eastwood Catalog. They have some rattle can paints specifically for radiators. Good Luck
    Stogy likes this.
  20. I had my radiator in my avatar powder coated Satin Black, cost $60, looks great and cools perfectly.
    Stogy likes this.
  21. Neighborwood
    Joined: Nov 7, 2010
    Posts: 37


    I boiled water for a living working at thermal electric power plants. Nuclear, oil /gas fired boilers, and gas turbine/boiler plants.
    Black receives all colors (light) and well into the radiant heat spectrum. Polished aluminum reflects all colors and into the radiant heat spectrum. That is why you see your pretty face the first time the radiator top tank comes out of the carton.
    Within the containment at a Nuc. plant ( Westinghouse PWR) all the reactor coolant lines are insulated with polished stainless steel. ( this stuff was massive) But it did reflect the radiant heat well, though the costs were a tad big.
    Stainless was used because of the possible chlorides in normal high temp insulation react with the stainless pipe used.
    Saying that to make a point that all materials have what is called a emissivity number. ( the ability to emit or receive heat) Black is 1.0. If considering blue or red they are around 0.9, the number for polished aluminum is 0.1 - 0.05. Less then one tenth to one twentyth the ability of matt black to emit or receive heat.
    I have used a thinned flat black to paint when needed to enhanse the ability of the radiator to emit as much heat as possible. Just enough to make it look black.
    If a thicker paint is used then the insulating qualities and the heat transfer qualities of the paint comes into the equation. This is why some who did the back paint job had unimpressive results.
    Hope this helps the discussion
    j hansen likes this.
  22. Painted my aluminum radiator flat black. Never noticed any difference in cooling capacity whatsoever.
  23. dreracecar
    Joined: Aug 27, 2009
    Posts: 3,113

    from so-cal

    Its not done for a reason
    its about $100 minimum charge now a days unless you know a guy
    anodize fades after awhile , quickly if in the sun and turns purple
    depending on who built the core, fins are either soldered or epoxied in place and the black dye will not cover over the epoxy
    57 HEAP likes this.
  24. OK
  25. Bandit Billy
    Joined: Sep 16, 2014
    Posts: 7,435

    Bandit Billy

    Another thread gave me a good idea for my next aluminum radiator, fake brass and copper patina. You can paint he core black, that is just fine but why stop there? A little antique brass paint on the tanks, streak some green with a q-tip, and presto, faux radiator patina. :cool:
  26. DDDenny
    Joined: Feb 6, 2015
    Posts: 14,573

    from oregon


    That would look great with about 150 drawer pulls in the grill too!
    Bandit Billy likes this.
  27. Blue One
    Joined: Feb 6, 2010
    Posts: 10,940

    Blue One
    from Alberta

    Cosmo49 likes this.
  28. Rusty O'Toole
    Joined: Sep 17, 2006
    Posts: 9,458

    Rusty O'Toole

    The black BBQ paint must be formulated to stick to aluminum since so many barbecues are made of aluminum. I know the stuff is tough as nails. I bought a black Lincoln the previous owner touched up with it, had a hell of a time cleaning it off. Also it is heat proof .
  29. Neighborwood
    Joined: Nov 7, 2010
    Posts: 37


    The difference will only be noticed if a heat load test is conducted under controlled conditions. Comparing the polished aluminum radiator against a flat black painted radiator.
    The '1' value given to flat black is indicating all heat ,100%, is emitted or absorbed and the .1 to .o5 for polished aluminum refers to only 10% or less is absorbed or emitted.
  30. Ned Ludd
    Joined: May 15, 2009
    Posts: 4,201

    Ned Ludd

    It depends on the frequency of the radiation. Colour makes no difference to the mid-to-LW infrared an engine typically radiates. Surface finish does: matter is better.

Share This Page

Register now to get rid of these ads!


Copyright © 1995-2021 The Jalopy Journal: Steal our stuff, we'll kick your teeth in. Terms of Service. Privacy Policy.

Atomic Industry
Forum software by XenForo™ ©2010-2014 XenForo Ltd.