Then you should scrap the parts and remake them to the proper material spec. That is the ONLY acceptable solution for production automotive parts.
There is some chance that these could be mechanically coated with Zinc Nickel. I'm assuming that they were supposed to be made from electro coated zinc nickel coil steel. What is your steel chemistry (IE 1008/1010 or 1075 etc) and rockwell. As carbon content and hardness increase, resistance to aqueous corrosion decreases.
Are these production PPAP'ed parts? Then you have no choice but to scrap and re-make. I'd then hunt down whoever allowed regular cold roll to be ordered/supplied/run and nail them to the wall. If you have a PO that specifies the proper material and its your suppliers fault then you might get them to pay you back for the steel and some costs, but they wont cover all of them.
Good luck!
Nick
I love materials science!