Is there any benefit to copper plating before nickel plating?

I know that in cosmetic 'triple chrome' plating copper is used under the nickel and chrome coats. This appears to be because it is easy to polish for a mirror finish on the end result. Is there any benefit to a copper coat under nickel when the main aim is corrosion protection of the steel component?

The application in this case, is some knurled 0BA screws with tommy bar holes through the heads that need replacing on a BCA jig borer.

It always used to be the case, but you may not need it with a modern nickel solution. There should be recomendations included with the nickel bath specification.

Yes,
A layer of copper improves corrosion resistance.

Robert G8RPI.

Having had a car bumper plated without a copper layer (not my choice) I can confirm Robert is spot on.

I remember years ago visiting the Premier Drum factory and seeing their electroplating system. All their metal plating was done in house with copper being the base layer. Their finish was impressive after much hand polishing both prior and after plating.

Yes, that is the reason for the Nickel coating to allow polishing of the item to give a better finish to the Chrome'

The original reason for the copper was that the nickel would not adhere well to steel directly, it was the thick layer of dull nickel that was mechanically polished prior to chrome plating.

And it is the nickel that provides the corrosion resistance by dissolving away instead of the chrome. That's why chrome plating flakes off around damaged areas - the underlying layer has gone. Nowadays they skimp on the nickel which is why modern chrome plating doesn't last so long.

.

Might it be cheaper/easier to make them from Stainless Steel ?

MichaelG.

Where's the fun in that?

HOW do you polish Knurling ? Noel.

I don't want to polish any of it. This isn't bright work, it's corrosion protection, like the originals tried to be.

Oddly, the dials, locking screws and other parts that were obviously made in-house were nickel plated, while the handles for the feedscrews are chrome plated - bought in.

Edited By Mark Rand on 30/08/2021 13:48:41

.

I am still struggling to identify these knurled 0BA screws … If they are the locking screws for the slides, I’m almost certain that mine have plain ‘capstan’ heads. [*]

Or are you replacing some after-market screws with the proper design ?

MichaelG.

.

[ *] ready to be embarrassed when I check

Edited By Michael Gilligan on 30/08/2021 14:46:57

Brain fart! The dials are knurled, the screws are (slightly) domed...

And yes, one of them on the Mk3 was replaced by a nasty mild steel bodge that's gone rusty.

Got a few way locking screws on the Beaver mill that need finishing as well.

Edited By Mark Rand on 30/08/2021 16:02:57

I believe chromium is porus so the copper and nickel provide the corrosion protection and highly polished layers, the Chromium provides the decorative finish.

Mike

.

That’s O.K. then

Thanks for confirming

MichaelG.

.

Edit: for anyone still confused … this is the style of screw which I believe Mark is making:

Adapted from : http://www.lathes.co.uk/bca/page4.html

Edited By Michael Gilligan on 30/08/2021 17:55:05

Unless you intend to keep the machine outside, I don't think there will be much difference between the two approaches.

Yes, I might just plate the nickel directly on the steel.

Michael:- Them're the ones. Even in the photo it's possible to see the colour difference between the handle and the dial, screw, dial gauge mount etc. Not that it matters.

Some bed-time reading for you, Mark: **LINK**

https://nickelinstitute.org/media/2323/nph_141015.pdf

MichaelG.

Get thee behind me satan, and push!