Yes, easy to make a mistake. But in today's world of instant information, it was easy.

Bought some Arm & Hammer Laundry Booster and Wash Soda (Sodium Carbonate) at wally world. That and a 2 amp battery charger and a length of cold rolled steel and some copper wire is all that's needed.

Don't use Bicarbonate of soda. Not the same thing.

As I wrote, no effect on factory bluing, or parent metal. Just the rust is removed.

I did not try it on any hardened steel.