Nickel plating zinc die castings for bathroom fixtures

A. Hi, Kashinath.

Ugh! Replacing brass with diecast for bathroom fixtures is a project I can't quite put my heart into :-(

I've always hated diecast bathroom fixtures because, instead of aging gracefully like brass, they become pockmarked with white volcanos and craters. Do you intend to tell the buyers that quality brass castings are no longer under the nickel, but they've been replaced with cheap diecastings :-)

Anyway, the essential elements of plating die castings are: assuring that 100% of the castings are plating quality (consistent finish, non porous, completely free of even the tinest cold-shuts), then properly mechanically finished; your brass pretreatment cycle will need only minor adjustments; then cyanide copper plate; then acid copper plate; then nickel-chrome plate as at present. Good luck.

Best of luck!

A. It will be a very difficult task to use zinc-diecast components in the production of bathroom fittings. The quality of the castings will need to be very good to start with, and the plating quality will also have to be very good to survive the contact with water/humidity. Here in the U.K. we do not find the need to use an acid copper stage. I would suggest a copper cyanide plate of at least 12.5 microns (absolute minimum) and then a high corrosion resistant electroless nickel. This nickel should again be plated to an absolute minimum thickness of 12.5 microns. It will be quite an achievement though to compete with the quality of plated brass components!

 Thanks for providing backup to my assessment, Joseph. I have seen older diecast parts used in bathrooms many times and they are always miserable and full of white mini-volcano pits. Yes, it's theoretically possible to plate the parts so well that nothing will happen to them for a fair amount of time. But the point will always come when the zinc is absolutely pit-ugly, whereas the brass would have aged gracefully, gradually revealing its smooth golden color through the thinning plating.

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A. Hi, cousin Hussain.

We appended your question to a thread that answers it. Please see if a library or a company in your area offers access to the Metal Finishing Guidebook ⇨

or the Electroplating Engineering Handbook .
to flesh out each of those process steps. This site is more about suggesting what books to read, or helping with problems that persist after the books have been read, than about printing excerpts from books :-)
Good luck.

Regards,

A. Hi Harit. Please try to plate a Hull Cell panel so you know whether the pitting is due to low quality Zamak (porous, cold shuts, poor removal of flashing, poor mechanical pretreatment) or due to a problem in the nickel plating bath (gas pits, etc.) or other plating bath. Gas pits sound more likely on a flat surface than on rounded ones. Do you know the surface tension in the nickel plating bath? What do the pits look like under low magnification -- bright and hemispherical, or deep and ragged?

Regards,