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Material Selection for Solar Energy Project

I am an engineer at a company in California where we typically design and build spacecraft. We typically work with aluminum, titanium and stainless steel alloys that will be in the corrosion benign environment of space. We are currently in the process of designing a commercial ground based concentrated solar energy system. We are designing the chassis from carbon steel that will be resistance spot welded. The problem is this material and service environment is new to us. Can you please provide me with some guidance on what materials are typically used and what systems are used for corrosion prevention. These will be out in the weather for several years. I am particularly concerned with how the faying surface between the sheets at the spot welds. Our structure would be very similar to an air conditioner housing or a cabinet that would be used outside.

Dave Bezaire
Materials And Process Engineer - Huntington Beach, California, USA
February 18, 2008

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Have you considered using weathering steels? Your application will be in the Mojave desert and should not be exposed to water very often. Weathering steels are commonly used in construction where the cost of painting, initial as well as maintenance, is prohibitive. US Steel used to make Cor-ten product that was advertised to have 1/10th the corrosion rate of plain carbon steels. The material is weldable and HSLA so you can reduce the thickness if stiffness is not an issue. Cost penalty is minimal and reduction in gauge more than compensates for the penalty per pound.

Otherwise, take a cue from the auto industry and have the whole thing dipped in E-coat. We get >10 years corrosion protection exposed to severe salt spray environment, crevices and all. There are paint suppliers in the midwest that can dip assemblies as big as a pickup truck and rotate them in the tanks to ensure complete coverage and no trapping of air bubbles.

Ilya Lisenker
Automotive - Dayton, Ohio, USA
February 26, 2008