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Painting a New Radiator

Rick Anderson

NAXJA Forum User
Location
Lusby, MD
Just got a new Radiator for my XJ.

It was $108 free shipping. From www.completeradiators.com
433871_large.jpg

The manufacturer is "Ready-Rad".

Its an aluminum core, and it came bare metal. I would think the thinwall aluminum would need a little protection from corrosion and I'm thinking of painting it.

Anyone have any suggestions on what paint to use on a radiator?

This is a single row core, but my existing radiator was a single row core as well. My old radiator had the typical tubes for the row, probably a 1/3" deep and 1/8" wide, leaving mostly unused space under the tanks with a shallow core inbetween them. The tubes on the single row of this radiator are a full inch deep, maybe slightly wider than 1/8" and takes up all the space under the tanks, the core (even though its single row) depth takes up all the space between the tanks.
 
My aluminum has gone through two winters and still looks new, bare metal. I think I'm gonna leave it that way and just wash it periodically. If I see any signs of corrosion, I might paint it. After it's oxidized a bit, the paint will probably stick better anyway. Many paints require a special primer for aluminum.
I think a few very lite coats of say, Rustolium grill and BarBQ paint, would cover enough without serious fish eyes, to get the job done. I wouldn't put the paint on too thick, I'd try for several very lite coats.
I recently painted a copper radiator that came blank, it's hard to get everything coated, without going too thick and getting drips and dribbles. Kind of a fine line between coating it and plugging it up.
 
Seems to me that painting a radiator may affect it's cooling ablility. The paint could hold in the heat, not to mention it could gum up the fins, not allowing air to pass through. Millions of vehicles have come from the factory with unpainted aluminum radiators...there's probably a reason for it.
 
Aluminum technically oxidizes quite easily, but the oxidation forms a microscopically thin hard protective coat of Aluminum Oxide on the surface, which prevents any further oxidation from taking place. If all you are throwing at it is air and water, it will remain corrosion free for years - without paint or any additional coating.
 
Don't paint it, the aluminun rads have a coating on them already that does not interfere with heat transfer. Most any paint you use will add insulation to the fins and thats not a good thing.
 
The term is anodized, and I don't think its anodized that usually changes the color and surface texture slightly and it looks like bare metal.

I'll look closer to see if there is some sort of coating, there could be coating that you can't really tell. Considering the low price I would think they don't go to the extra effort of coating or clear painting the core. If I can detect some sort of coating then I'll leave it as is, maybe I'll scratch it in a unconspicous spot and see if that shows me signs of a coating.

Yes, I worry about the effect of paint on the heat transfer, thats why I'm hoping there is some sort of special Radiator Paint designed to have a minimum effect. I haven't found any, but you see OEM and aftermarket radiators that have painted cores, so I'm sure there is a paint that has a minimum impact on the heat transfer.

I know aluminum oxidizes to form a protective barrier layer, BUT that doesn't always work, I've seen aluminum corrode thru (although it takes a long time and usually needs some extra help from something particularly corrosive) and thats my worry, that road salt and chemicals could give me a hole in the radiator after a couple of years.

If I paint it, still deciding, I may just leave it bare metal, but I've got an air compressor with a blow gun, I'll spray compressed air thru the fins before the paint dries, thus spreading the paint around a little better into the core and removing any clogging inbetween the fins.
 
Friend of mine has a shop, almost all the OEM aluminum rads have no color on them, only the copper cores. I just took one back for him to the local GM dealer for one of the big 1ton diesel's, almost as wide as the back seat of my XJ, aluminum and no color on the fins, $500 rad too....
 
Hmmm, maybe I'll just leave it bare aluminum.

Why paint copper but not aluminum? Copper also corrodes to form a protective layer and stop further corrosion. I'm guessing the protective corroded layer of copper is thicker and effects the heat transfer, while aluminum the protective corroded layer does not.
 
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