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Saturday, January 9, 2016

Reading List: Rust

Waldman, Jonathan. Rust. New York: Simon & Schuster, 2015. ISBN 978-1-4516-9159-7.
In May of 1980 two activists, protesting the imprisonment of a Black Panther convicted of murder, climbed the Statue of Liberty in New York harbour, planning to unfurl a banner high on the statue. After spending a cold and windy night aloft, they descended and surrendered to the New York Police Department's Emergency Service Unit. Fearful that the climbers may have damaged the fragile copper cladding of the monument, a comprehensive inspection was undertaken. What was found was shocking.

The structure of the Statue of Liberty was designed by Alexandre-Gustave Eiffel, and consists of an iron frame weighing 135 tons, which supports the 80 ton copper skin. As marine architects know well, a structure using two dissimilar metals such as iron and copper runs a severe risk of galvanic corrosion, especially in an environment such as the sea air of a harbour. If the iron and copper were to come into contact, a voltage would flow across the junction, and the iron would be consumed in the process. Eiffel's design prevented the iron and copper from touching one another by separating them with spacers made of asbestos impregnated with shellac.

What Eiffel didn't anticipate is that over the years superintendents of the statue would decide to “protect” its interior by applying various kinds of paint. By 1980 eight coats of paint had accumulated, almost as thick as the copper skin. The paint trapped water between the skin and the iron frame, and this set electrolysis into action. One third of the rivets in the frame were damaged or missing, and some of the frame's iron ribs had lost two thirds of their material. The asbestos insulators had absorbed water and were long gone. The statue was at risk of structural failure.

A private fund-raising campaign raised US$ 277 million to restore the statue, which ended up replacing most of its internal structure. On July 4th, 1986, the restored statue was inaugurated, marking its 100th anniversary.

Earth, uniquely among known worlds, has an atmosphere with free oxygen, produced by photosynthetic plants. While much appreciated by creatures like ourselves which breathe it, oxygen is a highly reactive gas and combines with many other elements, either violently in fire, or more slowly in reactions such as rusting metals. Further, 71% of the Earth's surface is covered by oceans, whose salty water promotes other forms of corrosion all too familiar to owners of boats. This book describes humanity's “longest war”: the battle against the corruption of our works by the inexorable chemical process of corrosion.

Consider an everyday object much more humble than the Statue of Liberty: the aluminium beverage can. The modern can is one of the most highly optimised products of engineering ever created. Around 180 billion cans are produced and consumed every year around the world: four six packs for every living human being. Reducing the mass of each can by just one gram will result in an annual saving of 180,000 metric tons of aluminium worth almost 300 million dollars at present prices, so a long list of clever tricks has been employed to reduce the mass of cans. But it doesn't matter how light or inexpensive the can is if it explodes, leaks, or changes the flavour of its contents. Coca-Cola, with a pH of 2.75 and a witches’ brew of ingredients, under a pressure of 6 atmospheres, is as corrosive to bare aluminium as battery acid. If the inside of the can were not coated with a proprietary epoxy lining (whose composition depends upon the product being canned, and is carefully guarded by can manufacturers), the Coke would corrode through the thin walls of the can in just three days. The process of scoring the pop-top removes the coating around the score, and risks corrosion and leakage if a can is stored on its side; don't do that.

The author takes us on an eclectic tour the history of corrosion and those who battle it, from the invention of stainless steel, inspecting the trans-Alaska oil pipeline by sending a “pig” (essentially a robot submarine equipped with electronic sensors) down its entire length, and evangelists for galvanizing (zinc coating) steel. We meet Dan Dunmire, the Pentagon's rust czar, who estimates that corrosion costs the military on the order of US$ 20 billion a year and describes how even the most humble of mitigation strategies can have huge payoffs. A new kind of gasket intended to prevent corrosion where radio antennas protrude through the fuselage of aircraft returned 175 times its investment in a single year. Overall return on investment in the projects funded by his office is estimated as fifty to one. We're introduced to the world of the corrosion engineer, a specialty which, while not glamorous, pays well and offers superb job security, since rust will always be with us.

Not everybody we encounter battles rust. Photographer Alyssha Eve Csük has turned corrosion into fine art. Working at the abandoned Bethlehem Steel Works in Pennsylvania, perhaps the rustiest part of the rust belt, she clandestinely scrambles around the treacherous industrial landscape in search of the beauty in corrosion.

This book mixes the science of corrosion with the stories of those who fight it, in the past and today. It is an enlightening and entertaining look into the most mundane of phenomena, but one which affects all the technological works of mankind.

Posted at January 9, 2016 22:20