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-----Silver plating on resistor terminal is oxidizing
Q. We are experiencing issues with oxidation on silver-plated leads(Resistor terminals) after 20 months of storage (though not on all parts).
We need to determine the effective storage period for silver-plated components.
Harish MahaleEngineer - Karnataka, India
January 28, 2026
A. Hi Harish
That looks nothing like silver tarnish to me, but a whole lot like iron rust. What material are these terminals made of please?
It is possible to talk about shelf life and anti-corrosive storage conditions, but let's start with the details of what actually happened if we can. Thanks.
Luck & Regards,
Ted Mooney, P.E. RET
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finishing.com - Pine Beach, New Jersey
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Q. Hello Ted, thank you for the quick response. The terminal material is made of mild steel with a coating of 1 micron Cu, 1 micron Ni, and 1.4 micron silver. After this coating, the stud will be spot-welded to the SS Cap and next assembly
Harish Mahale [returning]Engineer - Karnataka, India
A. Hi again,
I can't get a sense of scale from the photo, so there might be tolerances requiring such thin platings. But that thinness is almost surely the problem. Just for comparison sake, the thickness of nickel plating per ASTM B456 (nickel plus chromium coatings) is 10 microns for "mild conditions" and 20 microns for "moderate".
With a total thickness of 2.4 microns (< 0.0001") I would suspect porosity and pin-holes are exposing the steel. And copper, nickel and silver all being cathodic to steel, they are accelerating the rusting.
If you can't increase plating thickness, mechanically polishing the wire/stud before plating should help somewhat, as would cool low-humidity storage. Unfortunately, asking what the shelf life should be for steel components with porous cathodic plating on them will probably not be productive.
Luck & Regards,
Ted Mooney, P.E. RET
Striving to live Aloha
finishing.com - Pine Beach, New Jersey
Need quick confidential answers? $25
Need project assistance? $100/hr.
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