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Stainless Steel
Friday | 26 September, 2008 | 4:01 am

History in the making

By Liz Sommerville

September 29, 2008 - The New Doha International Airport is under construction in Qatar and is slated to partially open in 2009, with completion set for 2015. Once completed, the airport will feature the world's largest stainless steel roof at 2.1 million square feet. Contrarian Metal Resources, Allison Park, Pa., was chosen to supply the stainless steel finish for the airport's roof.

Overcoming obstacles
Contrarian began working with the airport's architects at the earliest stages of design to identify the type of material needed for the project. The company had to supply a material solution that would withstand the environment in the Middle East. Because the airport is on the Persian Gulf, Type 316L stainless steel couldn't be used because it would corrode, developing a red dust surface in that environment.

"If you're near salt water, Type 316L will usually perform quite well," explains Jim Halliday, president of Contrarian. "However, the Persian Gulf is among the most severe marine environments on Earth in terms of metallic corrosion. So we had to come up with a better solution."

At first, Contrarian believed titanium was the right choice for the airport roof, but it ran into problems when it discovered the material was in too short of supply at the time of production. "The titanium market got so tight in the last few years that we couldn't get the product," Hallidays says "So we had to solve the problem with another metal."

Painted aluminum and painted galvanized, Halliday explains, weren't sustainable enough. Contrarian even looked at using cupronickel but found it would have been too expensive for this large of a project. "We're primarily a stainless steel company and we felt a great motivation to solve the problem with stainless steel," he says.

Rising to the challenge
The company teamed up with ATI Allegheny Ludlum Corp., Brackenridge, Pa., to find a way to make stainless steel perform in the challenging environment. Their solution was Allegheny's proprietary AL 2003 lean duplex alloy, an economic alternative stainless that offers better corrosion resistance and strength compared with Type 316L. According to Halliday, duplex alloys are typically used on severe corrosion parts like offshore drilling rigs, but they're generally tough to form, making it challenging to produce a standing-seam roof. Lean duplex alloys have better forming characteristics, however. "It's just a little leaner," he says. "It still gives you the advantages of a duplex grain structure, which helps with strength and corrosion, but it has enough elongation to make a standing-seam roof."

Once the proper material was chosen, Contrarian was faced with another big challenge: how to produce a low-glare finish in stainless steel suitable for the airport's environment. The airport specified that Contrarian apply its proprietary architectural matte finish, InvariMatte, on the lean duplex stainless alloy for added aesthetic value and glare resistance. "InvariMatte has been used on austenitic grades, specifically Type 304 stainless and Type 316 stainless, for several airports," says Halliday. "But we had to figure out how to apply the finish to duplex alloy, which is complicated because duplex is harder to decorate."

Contrarian rose to the challenge and came up with a methodology to meet the glare spec, resulting in a uniform, low-glare finish that wouldn't rust. "We came up with a solution that's rather unique in the world of stainless steel," says Halliday. "To my knowledge, it's the first time anyone has made a duplex roof and also the first time anyone has rolled a texture in a duplex alloy. So there's some cutting-edge development here. It was a challenging assignment, but we solved it, I think, quite well." MM

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