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(March 2006) posted on Tue Feb 28, 2006

A fresh look at an everyday commodity

By Darek Johnson

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That mostly steel car you drove to work this morning was once a rock. Somewhere in its geological past, a smelting operation changed the rock -- iron ore -- into the metals used in your car. In fact, iron ore, in forms of magnetite, hematite, limonite, goethite and taconite, is a part of everything metal on your car, including the bauxite-based aluminum, because it contains iron impurities.

Of course, there's iron-free plastic in the car, too, but, because they make plastic from dead lizards, I try not to touch it.

Iron ore contains ferrous oxide, an oxidized iron that generally forms through the accumulation of iron-based minerals that have settled on, get this, bog water. In time, these minerals sink, accrue and form the ore. When smelted, the ore forms iron. Today, it's usually combined with alloys to become one of many types of iron or steel.

In the old days, there was wrought iron, cast iron or steel, each produced by heating ore in clay or brick furnaces, then putting it through a tempering process. These furnaces produced a molten iron glob, called a "bloom," from the iron ore rocks. That bloom was hammered -- "wrought" (thus the name) -- into flattened iron, making it strong and flexible.

Flexibility is a critical asset in any standing structure. In fact, the discovery of a "puddle" iron smelting process (where molten cast iron is reverberated with oxides to create a lighter and more flexible iron), in the late 1880s, allowed the building of the Eiffel Tower. Puddle iron allowed engineers to create the wide-span, iron arches we enjoy in early 19th Century architecture and bridge structures.

Consider these three essentials when choosing metal for a sign: correctness, cost and corrosion. Correctness means to choose the right metal for the job, such as annealed, cold-rolled steel when you need extra pliability for bending. Costs clearly affect a sign's price and your profit.

Controlling corrosion is a science. In steel, the choices range from such processes as galvanizing, "porcelainizing" or vitreous-glass coatings, to blending steel, chromium, nickel and aluminum into corrosion-resistant steel.

On quick jobs, six out of ten shops spray small sections with a Rust-Oleum&$174; coating followed with some quick squirts of Krylon®>paint.