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Rusty colored staining on 420 stainless steel

2005

I work for a coiled pin distribution company. We recently received a shipment of pins at our China operation that look "rusty". These pins are made of 420 stainless steel and are heat treated to HV 460/590. There is no oil applied to these parts, finish is natural.
Any idea of what this "rusty" coloration might be? What type of tests could be used to determine what it is?

L. Labbe
Distributor - Shainghai, China

2005

It is probably iron oxide, stainless steel will rust under the right conditions. To prevent the problem in the future, you need to specify acceptable appearance of the product along with your other requirements like hardness, tensile strength, etc.

If you do not want the parts oiled or otherwise coated, you may need to have them packaged in plastic, wrapped in paper, boxes, etc.

Tom Pullizzi
Falls Township, Pennsylvania

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