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topic 8623

Electro Plating/Electroforming


We face a problem of small Nickel growth in inner surface while plating on Nickel or chrome.The surface finish of product on which plating/forming is done is of the order 1 R a micro inch. The location of this internal protrusion varies from cycle to cycle. Lower current density or low ramp or changing bath brighteners have not helped. The growth is seen when plated part is removed as a formed part. What could be cause of such growth?

The prior degreasing/rinsing well or brushing base also has not resolved problem. What could be cause and remedy? Watts bath or modified Nickel platings have been tried. The size of growth could be 10 microns in plating thickness of 150 microns.

Tillary [last name deleted for privacy by Editor]
- Los Angeles California, USA


As I understand your question, you are electroforming on a flat sheet and peeling the electroform when it is complete. If the build-up is under the electroform around the edge below the mandrel surface then I believe you have a tensile stress condition in your bath. This causes the electroform to shrink as it is formed and thus lift around the edge. Check your stress carefully and adjust it to 0 - 1000 Psi tensile.

Russell Richter
- Danbury, Connecticut, USA


Thanks Russell.

The electroforming is done on a round object and not flat. The problem is not necessary on the edge but all over the length and diameter. The stresses are very much controlled but are not zero. The inner deposits occur only at 20 to 50 places and can be removed by mechanical method. The size of deposit is of 100/200 micron diameter and of about 15 micron height. The analysis has indicated mainly Nickel, sometimes Chrome (surface of object) and sometimes copper. The low pH has not removed such deposits.

Tillary [returning]
- Los Angeles California, USA

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