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Retaining the natural finish of exposed hot rolled steel structure in a new residence?

Hi,
I'm an architect working on a residential project in CT and we want to expose the steel structure on the interior as a decorative, industrial detail. We are using hot rolled steel members and I would like to express the natural blue/brown/gray finish that is characteristic of the material, rather than priming and painting it which hides it's natural beauty. The problem is this: if we erect the structure in the field, then frame the rest of the wood construction around it, it will be exposed to the elements for at least 2 weeks, and will likely rust which we don't want. I thought of wiping it down with vinegar [in bulk on eBay or Amazon] to clean the mill scale right after it's erected, then immediately applying a clear coat, but we are erecting it in December, and it's too cold to apply the clear coat before the space is enclosed. Can anyone tell me if a light sandblasting will remove the rust, but still leave enough of the original patina? Or if the sandblasting takes off the original color with the rust, is there another way to recreate that original finish through the application of a reactive chemical in the field? I appreciate any insight you can offer.

Lucien Vita
architect - Westport, Connecticut, USA
December 14, 2010

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Steel will likely rust indoors as well as outdoors. The "natural" state of steel is red/brown iron oxide (rust), and if left to its own devices, steel (iron) will naturally revert to that state unless you prevent it.
Prevention means either preventing oxygen getting to it (and air is 20% O2), or by placing a sacrificial alternate metal in contact to "mop up" the oxygen.

One problem with most barrier systems (paints) is porosity. All paints are porous to some degree, so the main difference is how long it takes the air/water/moisture from air to get through and begin the rust.

For an industrial natural look you could consider hot dip galvanizing.

Geoff Crowley
Crithwood Ltd.
Westfield, Scotland, UK

December 15, 2010

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You can probably accomplish what you want by wiping it down with boiled linseed oil which will polymerize and harden over a period of weeks. If you can apply multiple coats a few weeks apart, even better. If you still get some orange/red rust from exposure to water, rubbing with a coarse cloth and linseed oil will restore the finish.

Jeffrey Holmes, CEF
Spartanburg, South Carolina
December 16, 2010