It is necessary to electroclean before plating to remove oils, grease, rouge, passive oxide films, and other surface contaminants left over from manufacturing and polishing.
Electrocleaning utilizes a heated alkaline solution, low voltage direct electrical current (DC) and a stainless steel anode. The piece to be cleaned is connected to the cathode side (-) of the rectifier giving it a negative charge, using a stainless steel anode connected to the positive (+) lead of the rectifier, low voltage current is applied producing hydrogen at the cathode through electrolysis.
The hydrogen bubbles scrub the piece while contaminants are dissolved into the solution. (Note: Spring steel can be embrittled by hydrogen so an alternative process my be necessary.)
This process is followed by a thorough rinse in clean deionized (or distilled) water followed by a 20-30 second acid dip. The acid removes film left behind by the alkaline cleaner and activates the surface for plating. A simple and effective acid dip can be prepared using Sparex ® at 2.5 ounces per quart or 70 grams per liter (one-quarter it’s recommended pickling strength). And remember, NEVER steam a piece during this process.
The acid dip is then followed by a 2nd distilled water rinse to remove the acid before plating. (A double rinse is recommended if plating with a cyanide based solution.) The acid dip, also called neutralization, prevents the drag out of the electrocleaner into the plating solution, avoiding contamination and prolonging the life and quality of the plating solution. This also “activates” the surface of the metal prior to plating.
The rinse water should not bead on the piece after activation. Water should sheet off the piece. Any beading indicates an incomplete cleaning process. If beading occurs, repeat the electrocleaning steps above, change to a fresh electrocleaning solution, or consider using a different electrocleaner.
Electroplating is a process where each step reliant on the prior step, and is necessary for consistent quality plating.