I have some steel parts, half of which are cold rolled and the other half are hot rolled. The plating on hot rolled parts rubs off in sheets with the flat of my thumb. The cold rolled seems to have reasonable adhesion - I can’t scratch it off with my fingernail.
Total plating area on the hot rolled is about 4 cm2 The parts are larger and powder coated, but the area to plated is masked so that metal is exposed in the area to be plated. Plating current is around 2 amps. Parts were cleaned with soap and water, and then “Bar Keeper’s Friend” (mostly oxalic acid with a mild abrasive) and finally rubbed down with isopropyl alcohol.
The electrolyte is DIY copper acetate made by dissolving stranded bare copper wire in a 50-50 mix of white vinegar and 3% hydrogen peroxide. Anode is copper water pipe.
When initially submerged in the plating solution and power applied, some black ‘flakes’ appeared in the solution. Plating seems to ‘grow’ from one edge of the area to be plated area across that area.
Current for the hot rolled parts was adjusted about 2A for the ~4 cm2 area. Current for the cold rolled parts is 500 mA for the ~1 cm2 area. Plating bath temperature is ambient (about 85 F today.) Initial copper coverage requires a minute or two. I left part in with mild agitation for 3 minutes.
My basic problem is that I’m not getting adhesion of the copper plating to the hot rolled steel. I do not know the exact alloy of the hot rolled.
I’m guessing this is a surface prep issue, but I don’t know what to do/try.
I’m trying to figure out how to diagnose the issue. I’ve not found the magic search terms to peruse this.
Thanks in advance for any help.
