What Coating is this on Aluminum 6082 rods?

Q. Hi, I need help identifying the coating on 6082 aluminum rod profiles. Profiles are being used in cold forming/forging operation. Coating has dark grey color and dull appearance. EDX results from coated area shows: C, O, Mg, Al, Si, Fe elements that are already in 6082 composition. C and O may come from atmosphere or it can be said that coating is an organic material. I used torch fire to heat up the profile and coating started melting showing brown melt droplets and smelled like burning of plastic. DSC results showed 3 peaks whose peak maximums are around 63 C, 150 °C and 177 C. Looks like an organic coating or a coating with organic binder. It must be feasible for aluminum wire rod production (maybe dip coating?). What do you think about type and material of coating?