The Stovebolt Site Forums The Shop Area General Truck Talk Aluminum radiator question?

I have seen a lot of talk about replacing original radiators on the AD trucks with a new aluminum radiator. My question is, has anyone painted one of these aluminum radiators black so that they more closely resemble the original brass copper radiator? If so, what would be the correct process to paint an aluminum radiator so that the paint adheres well?

I see some of them now come black. Like anything you paint, getting the grease off would be first order of business. I would think a good light coating would be all you would want, nothing to heavy or thick. It would be kinda cool if you could get one black anodized, then you wouldn't be adding layers of paint.

Joe

You can in fact buy black paint specifically formulated for painting radiators.
It apparently helps heat dissipation and copes with high temperatures.
Like Joe H mentions I imagine like any paint job,good prep is the key.

If I can remember who sells it i'll post a link.

Edit: Here you go. Radiator black.

Available in gloss or satin finish and it's on special offer just now!

I am trying to understand how a coat of paint, even a thin one can help with heat dissipation. If so, then why don't the manufacturers of aluminum radiators paint the ones which they sell for high performance engines?
The manufacturing process for aluminum radiators is very neat and clean. Conversely, the soldering process involved in the manufacturing process for a brass radiator is not so neat or clean. I tried to clean and polish the tank on mine, but stopped due to spattered solder all over the place. Another reason to paint the brass ones is to prevent corrosion.
I have heard of the heat dissipation theory a number of times before, but I am curious as to the source of the science/physics/chemistry behind the theory.
Carl

I'm not sure Carl,I can't back up that claim but just going back to my VW Bug days,they also painted the engine tinware black for a reason.
I'm sure I don't need to tell you but Black will always absorb more heat than a shiny reflective finish.

I guess I'm thinking along those lines.....

No, I am with you, black will always absorb more heat, thus pulling it away from the water. They don't paint them due to cost, and the fact that they already work so good. You want to keep heat in something, paint it white, same for if you want to keep heat out, paint it white. The white paint reflects heat back towards the source. Black absorbs heat and passes it through.

Joe

Black paint doesn't help with the heat transfer.

you wouldn't want to do any more then just squirt some rattle can on it
you don't want several layers of primer and paint

My question is how in the world does the color of paint have any impact on heat transfer in the darkness under the hood. It is just paint, nothing magical. Now if you expose the black painted surface to sunlight, the opposite and undesirable effect would take place. The black surface would gain more heat, not dissipate heat. What am I missing?
Carl

it has to do with Planck's law Carl, "heat transfer" is thermal radiation .... don't question it, just accept that it works to use the right black paint

Bill

Great read Bill. One problem. Since the thermal radiation originates inside of the radiator and naturally moves in an outward direction away from the inside of the radiator, the black paint would need to be on the inside surface of the radiator for the blackbodies theory to apply.
If black paint applied to the outside of a heat radiating device actually increased the efficiency of heat transfer, every high efficiency heating and air conditioning unit on the planet would have such black paint applied upon them. They do not.
Carl

When I worked at a radiator shop we painted our finished jobs, BUT- - - -we held the spray gun at a 45 degree angle so only the outside 1/8" or so of the fins got painted. All the paint accomplishes is cosmetics- - - -for the ones we wanted to do the maximum cooling, like for race cars, we didn't paint those jobs.
Jerry

There was a article on GM going to Black on their engines from the Orange of a few years before. They did studies and proved that Black pulls heat away from their race car motors hence the change from Orange to Black on their engines of today.
62Blue
Don

We all know paint does not adhere well to aluminum, hence we powder coat or anodize. So I can't see how having even a thin coat of material that is not going to adhere well is going to do anything but insulate and deter the transfer of heat.

Just my 2 cents

I'm pretty sure the emissivity of a black body is orders of magnitude lower than what you get from the air passing through the rad. It'll have an effect just so small that it's negligible. The paint would pretty much be a cosmetic or protective addition rather than performance.

On top of that fact is, blackbodies hypothesis is just that, a hypothesis. Blackbodies do not exist in nature, as far as anyone has proven. Not to take anything away from the hypothesis, as it helps explain much about the universe. But the paint on the outside of our 60 year old truck radiators is not blackbodies.
Carl

http://newton.dep.anl.gov/askasci/eng99/eng99320.htm

Joe

I worked in a radiator manufacturing plant and in wholesale distribution of radiators and heatexchangers for 30+ years. My understanding is that radiators needed a coat of something to prevent corrosion and give them a finished look. The radiators we supplied to Peterbilt Motor Co before the mid 80's were painted a light gray. New aluminum radiators don't need paint. They are all one color anyway and don't discolor like copper and brass. The paint used was the least expensive and only a lite coat applied. Too much paint will insulate and slow down the heat transfer process. I think black was used to match the radiator support and inner fender color.

Steve

This is the most plausible explanation so far, IMO.

I painted the front of my aluminum radiator so that it's not so visible through the grille. I left the back and sides and the top tank bare aluminum. I just used regular black enamel and have no issues.