Plating on Leaded Parts

Q. We have to plate leaded steels with zinc. Can you give me a procedure that will work for such substrates? E. A.

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A. This is a problem that platers continually seem to struggle with. I have addressed this issue a number of times in the last 11 years and the answer does not change. Here is what I wrote in one of my earlier columns:
The lead (0.15–0.35% by weight) is added to the steel to improve its machinability. Lead smears on the part surface during machining and tends to act as a lubricant. Use of “standard” cleaning cycles does not remove all of this lead. The following cleaning cycle should remove the lead and give you a good clean surface for your electroless nickel plating. 

1. 1Soak clean.
2. Clean anodically at a current density of 90–100 ASF in a strong alkaline cleaner.
3. Dip in an acid such as acetic, fluorboric, glycolic or citric acid.
4. Rinse well between each step.
5. Proceed to your zinc plating step(s).

Proprietary acids are also available. Look in the PRODUCTS FINISHING DIRECTORY & TECHNOLOGY GUIDE under Cleaning Chemicals, Aqueous for names of vendors or do a search on www.pfonline.com in the suppliers database.