I started making custom car badges a few years ago. I machined them from thin aluminum plate and TRIED to get paint to adhere. I tried every type of paint, including the super durable, made for car wheels, won't chip, sticks like you know what to a blanket. I couldn't find anything that I was happy with. Yes, some did adhere fairly well, but not good enough. That's when I got into powder coating.
For those that aren't familiar with it, as I wasn't when I started, it is fairly easy and inexpensive to do. I bought a gun and some powders from Eastwood and a cheap toaster oven from Walmart. You need a compressor, and that's about it. It is super durable; you basically can't scratch it off. If you don't want the whole part coated you can mask it (high temp tapes are available) or sand areas off after coating. The stuff is not easy to sand or remove, but is by far the best coating for aluminum I've ever used. I use it often now on parts I make that I would otherwise just leave bare aluminum as it is so easy to do and looks great.
A motor mount for a Taig lathe powder coated:
A couple badges, hot out of the oven. These were coated with black, baked, the surface sanded off to leave the black in the machined areas, then coated with clear and baked again:
Rick