I had my Hyper flow cats polished

I'm not sure if I missed a step, but when I had brought my 360 in for a srping check up, I had the mechanic pull out the Hyper Floe cats do I can have them polished. They were very tarnished. The place I sent it to did a fantastic job at bringing them back to life. Only one problem. After they were reassembled and i drove the car home, they turned blue again! They are not easy to get to from the engine bay. I could probably access them by removing the rear wheels and liners and the wheel arches for hand polishing. My question is, is there something that can be done to eliminate or reduce the amount of bluing other than not driving the car ? Anyone with experience, please lend me your wisdom!

Thanks,

Lino