New Radiator - do I paint it ?

[1978FJ40project]

I have ordered a replacement radiator for my 1978 FJ40 - it comes unpainted ( polishes aluminum). This might be a very uneducated question , but can / do / is it recommended to paint it ? The current one on my FJ40 is painted black ... all help, clarification , shaming for the stupid question would be appreciated

 

[JackA]

If it's aluminum, I would not paint it.

 

[Weedhopper]

Radiator rebuilders and repairers paint them black. Your old one could be one if it’s obvious spray paint. But no, no paint.

 

[Mark Jennings]

Look on your other cars (newer cars) with aluminum radiators, the heat exchange surface (fins) are not painted. However, with that said painting the upper tank black shouldn’t be an issue.
And I think new brass/copper radiators are black...the reason....black is the best heat transfer color.

 

[1978FJ40project]

Thanks everyone for your responses !

 

[Splangy]

Look on your other cars (newer cars) with aluminum radiators, the heat exchange surface (fins) are not painted. However, with that said painting the upper tank black shouldn’t be an issue.
And I think new brass/copper radiators are black...the reason....black is the best heat transfer color.

huh? how does black paint transfer heat better than white paint?

 

[Steamer]

I didn't like the shiny bright aluminum showing through my grill from the front so I did a very light misting with flat black just on what was showing through. The rest is plain bright and shiny. Other than that, there's no need to paint an aluminum radiator.

 

[Cromagnon]

huh? how does black paint transfer heat better than white paint?

He didn't say paint, he said color, and he is correct. Look in any physics manual and black is the best heat transfer color. Some paints are better than others at transferring thermal energy and most of the good ones are indeed, black. Don't know why. I would paint the aluminum radiator black for aesthetics but that's just me.

 

[Mark Jennings]

This is a funny story....years and years ago I Hot Rodded air cooled VW engines. When we shaved the heads to bump compression, yep, they would overheat, warp the heads to the point valves would no longer seat. We screwed with this issue for an entire year and then I was reading an article on heat transfer surface area and color. So I would paint the cast iron fined cylinders black and bead blast the aluminum heads to give a rough texture (more surface area) and no more over heating issues.

Then I went to school and in a general physics class learned why black is a better heat transfer color. If your curious still, google up Blackbody radiation heat transfer or surface emissivities for different colors. It’s a,,,,cool...subject (pun intended, lol).

Last thought, ever own a black car vs. a white or silver. A white car reflects a great amount of heat and will stay cooler. Black cars absorb a ton of heat. Remember paint is the same color on the inside as it is on the outsid (lol).

 

[thebigredrocker]

My biggest concern would be paint pealing. There is probably some acid you could spray on the polished aluminum to etch it.

 

[Splangy]

This is a funny story....years and years ago I Hot Rodded air cooled VW engines. When we shaved the heads to bump compression, yep, they would overheat, warp the heads to the point valves would no longer seat. We screwed with this issue for an entire year and then I was reading an article on heat transfer surface area and color. So I would paint the cast iron fined cylinders black and bead blast the aluminum heads to give a rough texture (more surface area) and no more over heating issues.

Then I went to school and in a general physics class learned why black is a better heat transfer color. If your curious still, google up Blackbody radiation heat transfer or surface emissivities for different colors. It’s a,,,,cool...subject (pun intended, lol).

Last thought, ever own a black car vs. a white or silver. A white car reflects a great amount of heat and will stay cooler. Black cars absorb a ton of heat. Remember paint is the same color on the inside as it is on the outsid (lol).

So, I’ll be cooler if I wear white underwear instead of black?

 

[Mark Jennings]

Yes you will, lol

 

[Bear]

Would those be white boxers or briefs? Are we concerned about surface area?

 

[73fj40lc]

So, I’ll be cooler if I wear white underwear instead of black?

No you won't but your balls definitely be cooler. Your sperm will thank you for not giving them a heat stroke...

 

[eaj71]

So, I’ll be cooler if I wear white underwear instead of black?

Oh snap

 

[Splangy]

Yes you will, lol

The color makes no difference (all other things equal) unless it’s subject to light energy. Since I don’t walk around in just my underpants outside very often, the color of them would make no difference in how they dissipate or retain heat.

But enough about underpants...

Painting your radiator black would only be an esthetic concern. If anything, paint would only serve to limit heat transfer (regardless of color). This effect would be trivial and immeasurable unless you applied a silly amount of paint. Aluminum can be difficult to achieve proper adhesion with unless prepped with a wash or etch primer. If you choose to go this route, choose your primer and paint carefully.

 

[WarDamnEagle]

Radiators transfer heat through convection and emissivity. I assume that convection accounts for the majority of an automotive radiator heat transfer but there will still be some heat transfer through radiant heat. Black will have a much higher emissivity than polished aluminum.

I have an aftermarket, aluminum radiator in my FJ55 and I am debating whether to have the entire radiator powder coated black or just the top and sides. Leaning towards just the top and sides as I think that will take care of the aesthetics. I still have the OEM radiator and might re-core and reinstall it. It's black top to bottom.

 

[Splangy]

Radiators transfer heat through convection and emissivity. I assume that convection accounts for the majority of an automotive radiator heat transfer but there will still be some heat transfer through radiant heat. Black will have a much higher emissivity than polished aluminum.

I have an aftermarket, aluminum radiator in my FJ55 and I am debating whether to have the entire radiator powder coated black or just the top and sides. Leaning towards just the top and sides as I think that will take care of the aesthetics. I still have the OEM radiator and might re-core and reinstall it. It's black top to bottom.

Emissivity and color are not directly related. You’re confusing light energy into the discussion.

 

[Mark Jennings]

Heat and light are the same, just a different wavelength on the electromagnetic spectrum. Polished surfaces look racy but do not transfer heat as well as rough and whites and silver reflect, black absorbs and transfers. Black paint is black on the inside and dose not reflect heat radiation back into whatever’s painted. White paint reflects it back inside.

However, compared with the heat transfer coefficient of copper and aluminum, paint has a minimal effect, maybe .00001%....but it does transfer.

As for you white boxers....poor choice for keeping your butt cool...switch to black.....transfers body heat out. LOL

 

[WarDamnEagle]

Emissivity and color are not directly related. You’re confusing light energy into the discussion.

I never said emissivity and color were directly related and I don't think I'm confusing emissivity with light energy. A flat black body has an emissivity of 0.9+ and polished aluminum has an emissivity of <0.1 (with, as I'm sure you know 1.0 being the highest). I'm guessing that radiant heat is tiny compared to convection in an automotive radiator but in a house radiator it can be as high as 30%. Of course a house radiator has a very laminar boundary layer which impact the convection heat transfer significantly whereas an automotive radiator does not.

I certainly wouldn't paint my radiator black to increase it's efficiency but I would say as long as the film is extremely thin and you aren't impacting the airflow across the fins then I don't think it will hurt anything. Of course those are big ifs which is why I'm leaning toward just the top and sides. FWIW, Eastwood makes a very thin film black aerosol for radiators.