Hollow-tube steel: An effective weapon in the war against corrosion
Tuesday, October 01, 2013
Perhaps the most villainous enemies of commercial building projects are the two most basic elements of our environment: air and water. Moisture in the air is enough to begin the process of corrosion because, as the Tao Te Ching recorded more than 2,000 years ago, "Water wears away stone."
In response, urban planners have deployed a material that has shown some promising results as an inhibitor to oxidation. Sites around the world, from France to Japan, have successfully used hollow-tube steel in construction projects, and some have lasted for decades in extremely corrosive environments.
In 1979, French researcher Michel Tournay published an evaluation of hollow-tube steel building projects in association with CIDECT, the International Committee for the Development and Study of Tubular Construction. Tournay's paper, "Internal Resistance to Corrosion in Steel Hollow Sections," has only recently been translated into English, with a new introduction by the Corus Tubes company, a subsidiary of Tata Steel.
The theory behind hollow-tube steel is that denying the replenishment of oxygen from the center of the hermetically sealed tubes ends the oxidation process. One of the best tests of the concept came with a factory in Valenciennes in northern France. Hollow-tube steel was used to construct a sulfate shed, which housed baths of sulfuric acid and stood next to a pickling plant. Tournay noted that "the whole of the steel framework was situated in a particularly hostile atmosphere owing to the sulfuric acid emanating from the pickling bath operations."
Out of 48 samples taken after 15 years of service, 37 of the samples that had remained sealed at both ends maintained an intact internal surface. Four of the samples, which were originally open at both ends, were completely corroded. The rest had been badly sealed or compromised and saw some corrosion damage.
A similar result was obtained in reviewing lighting poles in Japan. After 11 years of service in an urban atmosphere, the steel surrounding water drainage holes at the base of the columns were tested with ultrasound. The corrosion was mostly recorded in fractions of a millimeter. Two of Tournay's conclusions were that the worst corrosion was found where the edge was welded to the base plate and that there was little relation between corrosion and the environment of the hollow steel construction.
In 2000, Professor J. Wardenier of the Delft University of Technology in the Netherlands followed up on Tournay's work with a research paper titled, "Hollow Sections in Structural Applications." Wardenier reviewed examinations of hollow steel constructions and concluded, "These investigations, carried out in various countries, show that internal corrosion does not occur in sealed hollow sections."
Today, the region of the U.S. that benefits most from hollow steel construction is Hawaii, where 70 percent of new homes have replaced termite-treated timber with hollow steel frames. The hollow steel not only resists corrosion in the salty air but also is easy to install, thanks to its light weight.
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