Removing Cad Plate

[morthman]

Could anyone point me in the right direction to a specification or a in house procedure I can plagiarize, to remove Cad Plating. The situation is; we have parts Cad Plated before they where welded, and I need a procedure to reference for the Engineering Order. If I could get assistance it would be greatly appreciated.

 

[aviat]

Chapter 6 of AC 43.13-1B gives means of corrosion removal and on page 6-39 it gives instructions buffing platings. You may be able to adopt it for your situation because buffing will take the plating off.

 

[swall]

I would be leery of buffing cadmium plate, as cadmium dust is toxic.Also, any partial removal of the cadmium would be risky. Any that remains could cause liquid metal embrittlement when you weld.I would return the parts to the plating vendor and have them stripped, and then baked for hydrogen embrittlement relief.Then you can weld and replate.

 

[morthman]

aviat & swall, Thanks for the response. I have sent
the parts to our plating vendor and will be using
ammonium nitrate to remove the CAD Plate. Then they will be
welded and Cad Plated per ASTM B766.

swall, you state the parts should be stripped and then to have hydrogen embrittlement relief. Isn't that done after?
Cad Plating.

This is what our note reads on the drawing.
Finish: ASTM B766 Cadmium Plate
Class 12
Chromate Yellow, Type II
Hydrogen Embrittlement Relief

Again thanks!

 

[yates]

I would agree with swall, buffing off cadmium is not a good idea for health reasons. Also, being very soft and 'buttery' cadmium cannot be removed completely and would pollute subsequent welding. Stripping cad plate in a solution of ammonium nitrate is by far the best solution.
Most aerospace specifications require hydrogen embrittlement relief after removal of cad plate by ammonium nitrate, unless re cad plate can be guaranteed in the four hours following stripping.