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-----Why aren't aluminium pipelines used for oil and gas?
Hi, I am Chika, presently on an internship program with Shell in the corrosion unit. Now going through my college understanding of corrosion I know fully well that aluminium is a good corrosion resistant metal, due to its ability to form an oxide which stops it from further oxidation. Then I ask why we use stainless steel rather than alumium alloys, which I believe would be more resistant and even lighter for our oil and gas transportation.
Intern - Portharcourt, Rivers, Nigeria
June 23, 2011
You are confusing terms and phenomena. Aluminum is resistant to oxidation, not reduction (corrosion). In the presence of oxygen its surface oxidizes forming Al2O3. Once in this state it is extremely resistant to the stronger oxidants like nitric acid. But its protective layer is attacked in seconds if exposed to reducing (corrosive) environments such as found in many petroleum and natural gas products. Once penetrated, the failure is catastrophic. Also, there is the mechanical resistance issue. Even the stronger aluminum alloys are below mid-cost steel alloys. They do not present a fixed fatigue limit, so are rather unpredictable. When subject to high temperature they creep or even melt without advanced color warning which is very important for safety. In sum, no aluminum gas pipes. G. Marrufo-Mexico
Guillermo MarrufoMonterrey, NL, Mexico
June 28, 2011
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