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Rack marks on electropolished stainless steel

I am receiving stainless steel (304) wire parts that have been electropolished. There is a bad rack mark on them that the supplier says is unavoidable. It looks like a hole in the plating on a plated part, like a small crater, and black at the center. The entire mark is about 3mm dia, and the black mark about 1mm dia. I suspect that this is from a lack of good electrical contact. Can this be avoided? How? Can the mark be buffed out? FYI, these are being racked on 5mm dia brass rod. I am suspicious that they are being electroplated, not polished, but I don't know how to tell for sure. It is definitely stainless steel rod.

Steven Snyder
China Sourcing - Washington, DC, USA
2003

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2003

Steven, we don't want to harass you as reward for your confidence in us, but frankly you don't present the facts that anyone would need to even start suggesting improvements. What is the electropolishing specification that you and the shop are supposedly working to, what electrolyte are they using, and what total lack of control would allow you to suspect something as outrageous as the jobshop might be plating parts when they've been ordered to electropolish them? Is the shop ISO registered?

In a theoretical sense, yes, it may be impossible to eliminate rack marks. In a more limited sense, though, it sounds ridiculous to me for a shop to assert that an eye-catching black mark that looks like a hole cannot be improved upon. It sounds like the burn is make-and-break contact, and you probably should reject the whole lot (although it's difficult to tell from here). Certainly it is possible (although perhaps not practical) to wire these parts with multiple thin copper wires rather than hanging them on 5 mm brass rods.

You need to get the process control manual from this shop and spend some time there building your confidence that they actually follow it.

Ted Mooney, P.E.
Striving to live Aloha
finishing.com - Pine Beach, New Jersey