Steel

CARBON STEEL IN ART & ARCHITECTURE

*Although we do not offer supply only sheets of steel, we are happy to custom fabricate based upon your project’s needs. We selectively partner with vendors offering the highest quality materials available in many sizes and thicknesses. Please call for details.

Steel is usually considered a utilitarian material, better used as a skeleton, hidden from view by the beauty of another material. However, steel can be a very intriguing surfacing material under the right conditions — and with the right alloys.

When steel is first manufactured, its mill-finish has a blue-gray appearance. Steels, if exposed to moisture in liquid or gaseous state, will develop the characteristic red rust. If exposed to heat with chemicals, it can be blued or blackened. The surface can be polished, distressed, oiled, stained, and enhanced in ways many other metals only try to duplicate. Steel can be treated with wax or oils or they can be coated to maintain the surface finish and resist corrosion.

While stunning in its possibilities of finish, steel brings difficulty in protecting these tones as weather and atmosphere pose challenges. The problem to overcome with steel is its ever-changing, ever-deteriorating nature. Steel’s natural oxide is soluble and thus it continues to seek oxygen and water until only dust remains.

There are a number of steel alloys, some of which offer greater permanence, such as weathering steel. Weathering steel is also known as the product name “CORTEN” as well as copper-bearing steel for its copper alloying constituent.

Weathering Steel can be pre-weathered to reach deep and blues and maintain a more stable appearance and reduced staining. If your desire is a deep rusted aesthetic, this material provides a solution to the age-old issue of the deterioration of steels and bleeding of weathering steels.

Carbon steel A-588 Alloy (Weathering Steel) with mill scale apparent.

PHOTO © A. ZAHNER COMPANY

In addition to these natural appearance patina surfaces, there are a number of induced finishes which can be created on steels. Many people want to reproduce the look of mill-finish steel. This is possible, but will require maintenance in exterior environments.

Blackened steel is an artistic surface with a historic appearance. It can be made in a number of ways. One such method uses blackening or bluing chemical agents. These can be applied in a controlled environment to bring the steel to an artistic and blackened state. There are a number of patina solutions which can darken the steel for artistic effect. A blackened surface can be also created on galvanized steel sheet, which is essentially a steel with a zinc surface. This black patina is created by chemically patinating the zinc surface to a blackened state.

Heating the steel surface in the presence of steam creates a blue tone. This process, known as bluing, will create a more corrosion-resistant surface, at least for interior exposures. Other bluing processes using proprietary chemistries are available. It is possible to seal the surface with clear coatings or wax to maintain the color and resist further oxidation.

Hot-rolled vs Cold-rolled Steels

There are two distinct forms of plate and sheet steel available for the various alloys of carbon steel: hot rolled and cold rolled.

Hot rolled steel has a course, grainy surface with dark streaks. This grainy texture is the result of removing the deep scale during the pickling process. Scale is a hard, glass-like substance that forms on hot rolled steel. Pickling baths of sulfuric and hydrochloric acid remove the scale and the surface oxides. When this occurs, small textural rivulets are left on the surface.

Cold rolled steel has a smoother appearance, and is available in thinner gauge thickness sheet than hot-rolled steel. Cold-rolled steel is produced at the mill by rolling of hot rolled product through subsequent cold rolls.

There’s More To Discover About Steel

Take a deep dive in our three part blog series on Steel:

Custom perforated Solanum™ Weathering Steel by Zahner®

Photo by Matt Eames, ARKO | © A Zahner Company

Part 1

The Fascinating History of COR-TEN and Weathering Steel

A paradoxical group of materials, where decay is a feature.

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Photograph of the header panels before installation on Spaceport America.

Photo © A. Zahner Company.

Part 2

Weathering Steel Pt. 2 History & Science of Weathering Steel

Improving weathering steel by developing an impervious surface and deep hues prior to installation.

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Part 3

Weathering Steel Guide Part 3: Preweathered Solanum Steel—The Next Generation of Weathering Steel

An exploration of the advantages and applications of preweathered weathering steel.

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The Ultimate Steel Guide

Steel Surfaces: A Guide to Alloys, Finishes, Fabrication and Maintenance in Architecture and Art (Architectural Metals Series)

By L. William Zahner

Steel Surfaces, fourth in Zahner’s Architectural Metals Series, provides a comprehensive and authoritative treatment of steel applications in architecture and art. It covers everything from the history of the metal and choosing the right alloy, to detailed information on a variety of surface and chemical finishes and corrosion resistance. The book also features case studies that offer strategies for designing and executing successful projects using steel.

Learn More About Steel Surfaces