Replacing radiator (opened new one to find this. Need help.)

Hey folks. In garage now with car torn apart. Opened replacement radiator to find a small portion of the radiator (about the size of a quarter) is not coated in the silver coating like rest of radiator. Fins look ok and bar looks ok. No damage other than just no coating.

Is this a big deal/show stopper?

I need to get this done and thought I could just paint that spot with some radiator paint and move on, but not to sure. I haven't even unpacked the thing all the way yet, so sending back is option but need to get done ASAP. For background, it is my son's car and he is headed off to college in it Friday. It is an E90 328i - not a collector vehicle or "racing" situation. Daily driver for son at college. 

Paint it and move on, or send it back for new one and burn midnight oil to get it in before he leaves? 

Thanks!

Are you sure that's not black paint? The rest of the radiator looks to be aluminum. 

I would just install it as is and not even stress about it. 

Is the area raised or a different texture? It might be a fixed leak.

Install it and forget about it. I've seen stuff like that before on radiators but never even slowed down to mull it over. Never had a problem.

Thanks for questions! Yeah, it is not paint, or raised, or different texture. The photo does make it look like paint, but it is actually bare in that spot. I can see on close inspection that the silver coating just stops in that spot. It is bare aluminum on those two bars and the fins in that circular area; the rest of radiator has some sort of coating on it. Like they had their thumb (or something) over that spot when they coated it.

Thinking I will just paint that spot to give it some corrosion resistance and move on. 

If aluminum,  nothing required.  It doesn't corrode enough to be an issue.

Thank you all for the help!!

You don't need to paint aluminum. It forms an oxide layer and doesn't react with the surrounding environment.

I put it in and buttoned everything. No leaks! Success! Things always seem easier putting back together than taking apart. Glad it is done. Thanks for the help everyone!