Plating an I.D. with Zinc

Question:

We are planning to manufacture parts that are tubular in shape and require plating in both the O.D. and I.D. One such part is approximately nine inches long and has an O.D. of 0.8 inch and an I.D. of 0.5 inch. The parts are made of steel. A number of people have suggested plating the part with electroless nickel and at least one individual suggested zinc plating with a chromate conversion coating. What are your thoughts about this? A. R.

Answer:

Based on your description of the part, I am afraid that you have only one solution and that is electroless nickel. Trying to get the entire I.D. plated with zinc or any other electrolytically deposited metal is going to be difficult without resorting to fixturing and the use of special anodes. The I.D. is rather small and using a conventional zinc plating bath will not allow you to throw more than 0.5 – 1.0 inch into the tube. EN on the other hand should do the job for you as long as you use a vendor who knows his way round parts with small I.D.s.