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Cadmium plating peeling, leaving black residue after storage in VCI wrap

2005

We've just had an entire lot of cad plated parts returned from an aerospace customer -rejected for "peeling cad".
I agree that there is a degree a peeling, but it's isolated to what appear to areas of the part that were directly in contact with the VCI paper. The parts were returned to us still wrapped in the original VCI paper that we shipped them out in 6 years ago. These are flanged, cylindrical parts. The other curious thing is a black, powdery residue on the wrapping that coincides with the "peeling" cad.
Is there an environment that would attack or degrade cadmium plate like this? Is it unreasonable of our customer to expect cad to hold up after 6 years of storage?

Gail Grenert
machine shop quality manager - South Bend, IN, USA

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2005

I am ashamed to admit that I do not know what VCI is.

What was the base metal? Was it 4000 series steel that was not adequately "activated" and after 6 years the stress in the contaminated cadmium deposit just flaked it off?

Heaven forbid, did they put copper on under the cadmium and after 6 years next to sulfur the copper migrated thru and formed black copper sulfide?

Or was it cadmium over leaded brass that was not properly prepared and the cadmium is flaking off the lead?

Or ,was it leaded steel, the cadmium did not bond to the lead on the surface (it would have with proper prep) and after 6 years the stress in the contaminated cadmium broke loose from the lead that it was just laying on top of and not bonded?

Come back, give us more information.

Robert H Probert
Robert H Probert Technical Services

Garner, North Carolina

 Ed. note: VCI is Volatile Corrosion Inhibitor.

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Probably the parts or VCI paper got damp somewhere along the line. They want to hold you responsible for parts which they have had for six years?

The usual guarantee is : if your incoming inspection accepts them, you own them.

Maybe they're too good a customer, but I'd laugh anyway if a customer wanted to reject parts after six years on their shelf.

Jeffrey Holmes, CEF
Spartanburg, South Carolina
2005

These parts were manufactured from 4340. Because the peeling is only in the areas bearing the weight of the part, I'm inclined to believe the customer allowed a liquid to "pool up" in the packing container.

Gail Grenert
- South Bend, IN, USA
2005

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4340 requires special activation and most job shop platers doing cadmium have no idea how to do it. The cadmium is laying on top of nickel oxide and in time just pops off. To bond the cadmium to 4340 the plater must use a nickel chloride strike.

Robert H Probert
Robert H Probert Technical Services

Garner, North Carolina

2005

VCI is a very generic term. There are different chemicals coated on VCI paper for different metals. Some are reactive to non ferrous metals. It could be that the VCI manufacturer did not tell you this and gave you a wrong paper for your application.

Mukul Sareen
- Ludhiana, India
October 12, 2008