What did you use to do that? I used Eastwood radiator paint on my Jetta's front mount intercooler to make it black: I was thinking about doing the same to the MINI's intercooler
Radiator paint is originally meant for steel shell radiators that need help with both conductivity and rust prevention. Modern import radiators and intercoolers are constructed of aluminum, which resists oxidation better than steel. A conventional paint on aluminum would serve as a barrier to heat exchange; a thermal dispersant coating would be appropriate for those two applications. The MINI’s radiator and intercooler have a neutral color coating that can be seen under magnification. It appears to be a plasma coating, but it could be a phosphate, in either case it serves to guard against oxidation. The aluminum radiator Nitrominis has shown us evidently did not have a coating because it tarnished when handled; but a thermal dispersant is not available in red, only black. Nitrominis’ anodizing is a way to place a film over the substrate to obtain anti-oxidation properties without diminishing its thermal conductivity.