Wierd new way to copper plate cheap stainless steel

[kingtaco]

Howdy all, first time poster, long time lurker. While I'm having my plating room built, I've been doing some "kitchen chemistry" plating copper along with using caswells silver plug&plate.

A mention about the silver plug&plate: Didn't try with the stainless anode, but a .999 fine 1oz bar instead. used as a "brush" it plated ok, but lots of smut and tarnish. as a dip it plated perfectly.

Now back to the copper plating.

I'm used to acid copper plating. My solution is 450ml distilled water and 50ml Hardware store grade muriatic acid (38% iirc) I have a dual voltage current limited laboratory grade power supply, probably built in the 60s. It can supply on each channel 1A upto 20V or 0.5A up to 40v.

I hook one channel of the PSU up to my breadboard where I do my current limiting. I have 8 2.2K 1/2W resistors in parallel for a combined resistance of about 270ohms. I have caps placed both before and after the resistor array to make sure the power stays consistent.

When acid plating, I adjust the voltage to between 4 and 6 volts, to get a current of 0.1A(about appropriate for the size of what I'm plating.) I can plate quarters like a pro with this setup.

Now, I'm attempting to copper plate a cheap "18/0 Stainless Steel" fork. I was able to get copper onto the fork, but it wouldn't stick. I reread the plating manual and it says you can't plate acid copper directly to stainless steel.

Now, since I have a ruined fork, I decided to mess around a little. I made a solution of 500ml of boiling water, and added as much baking soda as would dissolve. I added a copper cathode and hooked the fork up as the anode. Exactly the opposite I would do if I were acid copper plating. In order to get any current through the solution, I have to run my PSU at 20V. That is giving me 0.15A of current. The copper is plating onto the steel!

The solution is also turning a deep blue, with what appears to be some sort of salt accumulating at the bottom. I keep the plating container(a pyrex 2 cup measuring cup) in a pot of boiling water to keep the temperature up. The plate is darker than the acid copper, but seems to adhere well. It also seems to have a smaller "grain" than the acid copper.

I can't explain what's going on here, but it seems I've found a new way to plate copper onto stainless steel.

Discussion is welcome as I'm not sure why what I'm doing is working as well as it seems.