Sunday, April 7, 2013

Trying to Strip Nickel Plating From Brass Fittings

The fitting that I plan to use in my vacuum pick-up tool arrived the other day, so now I can get started on making a handle for it.  The fitting is a nickel plated brass male Luer lock to 1/4" - 28 UNF thread connector.
Luer Lock Fitting
1/4 - 28 UNF thread
Luer Lock Fitting
Male Luer lock thread
Luer Lock Fitting
Luer lock fitting
My plan is to attach the fitting to the hand piece in the image below.  I can cut the brass piece to the size I want and then connect the Luer fitting to it.  To make sure the fitting is secure and has no chance of coming undone I've decided to braze it in place.  To do this I need to strip the nickel coating off the brass Luer fitting.  I think you can braze nickel plating to brass parts, but I'm not familiar with it, and because the Luer fitting cost $40 I want to stick with what I know.  I should point out that I'm just going by trial and error here.  I just trying things and seeing what works.
Brass Pipe
Brass hand piece

My first attempt to take off the plating involved leaving the fitting soak in vinegar overnight.  I didn't think it would do anything, and as expected nothing happened, but it was worth a shot.
luer lock fitting
Fitting in Vinegar
Next up I decided to try electrolysis to strip the plating.  I've had some experience with it in the past and am aware of things to watch out for.  I fed a wire through the fitting and flared the end of the wire.  By pulling this back, the threaded end of the fitting could be suspended in the electrolyte without the rest of the object being submerged.
luer lock fitting
Electrical connection to fitting
I used the vinegar from the first part of the experiment with some salt in it as the electrolyte.  There was likely to be some pitting, but since I'm not interested in the thread, it doesn't matter if it's slightly damaged.  A small current from a lab power supply was applied to the apparatus for several hours to perform the electrolysis.

The results weren't that great.  The coating was being stripped unevenly, with some parts disappearing quickly while others were left untouched.  One unexpected result was that the surface of the metal started to take on the salmon pink colour of copper.  To me, this indicates that the zinc from the brass was being removed leaving the copper behind.  Did not expect that.
luer lock fitting
Fitting undergoing electrolysis
After my first couple of attempts didn't work too well I decided to use some elbow grease and got to work with a small file and some steel wool.  As you can see in the images below, the thread and the flat part below it have taken on the familiar yellow colour of brass.  I may need to make some further modifications but until the hand piece I ordered turns up I can't really be certain.
luer lock fitting
Fitting with brass exposed
luer lock fitting
Fitting with brass exposed

2 comments:

  1. Silver solder will adhere to both the nickel and the brass with no problem. Use a propane torch with map gas. It makes a hotter flame.

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    1. Thanks for the tip. Funnily enough I ended up using MAP gas to do the job. Good to know for next time.

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