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Pickling and Passivation: What Your Stainless Round Bar Should Get Before Shipping

A hot-rolled stainless round bar doesn't come out of the mill shiny. It comes out grey, scaled and blotchy - the oxide layer formed during hot rolling and heat treatment. Pickling and passivation are the two steps that turn that surface into the stainless look everyone expects, and the difference between bars that get them and bars that don't shows up within months.

Pickling comes first. The bar goes through an acid bath, usually nitric-hydrofluoric, that dissolves the thick oxide scale and the chromium-depleted layer underneath it. Skip it, and the surface stays dark and uneven, with embedded scale that can later become a corrosion site.

Passivation follows. A nitric acid treatment removes free iron picked up from tooling and handling, and strengthens the natural chromium oxide film. The bar doesn't get shinier - that's polishing - but it does get its full corrosion resistance back. If your bar shows mysterious rust spots after a week outdoors, missing or poor passivation is the usual suspect.

When you order, say what you want: pickled and passivated for the standard hot-rolled finish, peeled and polished for a bright machining surface, or as-rolled for parts that get machined all over anyway. The price difference is real, so paying for a finish you'll cut off is wasted money - but skipping it on a visible surface is a complaint waiting to happen.

We supply stainless steel round bar in 304, 316L, 410 and other grades, with pickled, peeled or polished finishes to match your drawing requirements.
 

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