Solanum Steel™

Weathering Steel, Preweathered

Solanum Steel™ is a Zahner-developed pre-oxidized weathering steel that provides artists, architects and designers with a range of resonant tones on an enduring surface. The surface is produced by accelerating the natural weathering process and stabilizing the result.

The Genesis of Weathering Steel

In the early 1980's, L. William Zahner coined "weathering steel" to describe a range of steel alloys which exhibited resistance to atmospheric corrosion as compared with conventional steels. The surface became popular among designers shortly thereafter, and was commercially known as Cor-Ten, a product whose trademark is owned by US Steel.

Over the years, the popularity of the weathering steel material has risen and fallen, due to the reality that the material fails to resist corrosion in certain caustic environments. Although there are many people who appreciate the visual nature of the warm hues of weathering steel, nobody likes it when the material's color bleeds onto other surfaces. Zahner developed a material finish that changes this.

Introducing Solanum Steel™

Solanum Steel™ is an advancement over the traditional weathering process of weathering steel. Named for the dark bluish-red eggplant genus of the same name, the surface of Solanum Steel™ has a similarly deep red wine-colored tone. Made from the same alloys as Cor-Ten, Solanum Steel™ achieves an insoluble finish that repels water and reduces bleeding.

Zahner has more than 40 years of experience and nearly a hundred projects successfully installed using weathering and pre-weathered steel surfaces for architecture and art. The Zahner shop is clad in weathering steel. When it comes to engineering, fabricating, and installation the material, there is no other company in the world with as much experience and expertise in the use of weathering steel.

Using Solanum Steel on Interiors and Exteriors

Solanum Steel has been used on many interior applications in addition to its traditional use as a durable exterior surface. For interior surfaces, the material can be sealed with a clear coating to provide a softer touch. Sealing is not recommended for outdoor applications because the coating will require further maintenance over time.

Photo of Photo of the interior Solanum Steel™ application. Light flows through the perforations on the surface of the metal

Photo of the interior Solanum Steel™ application. Light flows through the perforations on metal's surface.
Photo © Ema Peter.

The Guggenheim Museum in Las Vegas

The Guggenheim Museum in Las Vegas.

Developing the Solanum Steel™ Patina

Solanum begins at the raw steel ingot. Zahner has close relationship with both the steel mill and the rolling mill, and is able to influence the quality of the surface long before the raw sheet arrives at Zahner. This ensures that the material is derived from specific alloying components and that the base raw material is cast to exacting specifications.

The ingot is then processed by Zahner's rolling mill partner, whose finesse with steel ensures that the surface is properly treated. In some ways, this is the most important step, because if you don’t influence the base metal sources the mill will treat the material like basic steel. If the mill treats the material like basic steel, contaminants will reveal themselves in the final product as streaks, rings, and discolorations in the finished surface.

Zahner patina engineers inspect each and every plate surface. Each surface of the bare Solanum Steel™ is cleaned and prepared to eliminate oxides and contaminants. If this step is not carefully followed the finish will not hold up. Once properly prepared, Zahner force the surface to an initial ferric oxide. This finish is slightly orange in color and is characterized by a crusty texture.

An orange patina is not as permanent as a dark patina. A patinated steel showing yellow and light orange colors will rub off and continue to bleed and stain adjoining surfaces, unless sealed with a durable coating. Zahner allows the orange-toned oxide to grow to a point, and then remove most of it from the surface. The surface is then exposed to a proprietary bath with specific atmospheric conditions to develop a hydrated oxide form of either ferrous oxide or ferrous hydroxide.

At this stage, the material is insoluble.

The hydrated oxide form until it reaches a certain point. The material is then arrested with a final bath that inhibits and slows oxidation to a standstill. The material is in its final stage of development.

Reducing the Staining from Steel

A sealed Solanum™ finish does not come off when rubbed, nor does it stain adjoining surfaces. The preweathering process for Solanum Steel™ reduces, and often eliminates, staining of surrounding surfaces.

Projects Using Solanum™ Steel

Get in touch with a Zahner representative to learn more, or download the Solanum Steel™ Booklet to share with clients.

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