Aluminum dye...?

[doctorpimp]

Is there any type of product that will dye aluminum?
Something that will produce a chemical reaction to change the alumunum to black.

Kind of like the Bluing used on rifle barrels etc...

I don't want to cover my aluminum rad with paint (kills efficiency), but I want to black-out my grill...

[FLG]

How about radiator paint?

They sell paint specifically for car radiators.

[vancamp]

try this but yu would need quite a bit.

[Mike DC]

Just tailgate a raggedy old commercial diesel truck in city traffic for about half an hour.  Then hose off the exterior of the car only.  Problem solved. 

[OttawaCharger]

You could anodize it. 

[375instroke]

Look at this stuff:
http://www.birchwoodcasey.com/metal/aluminum.html
https://www.birchwoodcasey.com/store/antiquing.html#oxd

[doctorpimp]

Thanks guys, but they all look a little costly...

[plum500]

Is there any sort of louvered/screen/grate you could fab to put in front of the rad and black that out -- still allowing the airflow, but visually blocking the view of the aluminum rad?

[doctorpimp]

Maybe... I still didn't want to hamper flow of cool air. 
Don't mind the asthetics of seeing the aluminum - as long as the trade off is a cooler engine...

[plum500]

Yeah, .. hmm, for that matter, if you really want the grill blacked out, could/should probably stay away from the rad anyway. Do something that will blackout the back of the grills next to the lights -- would think there would be still loads of air coming in up over the valance? Dunno...