Steel fuel tanks offer optimal cost, mass and sustainability

Automotive fuel tanks made of steel offer more than 100 years of proven safety and performance. Today steel offers the best combination of cost, mass, and sustainability

No doubt a short-term shift has occurred, with many automakers moving from mild steel to polyethylene (plastic) fuel tanks in search of lighter alternatives to increase fuel efficiency. However, with today’s increasing priority for emissions reduction, capacityand mass optimization, new grades of steel and manufacturing processes once again offer the most advantageous combination of cost, mass, and sustainability.

The latest generation hybrid-electric fuel systems present unique challenges which have been addressed with steel fuel tanks in vehicles like the Chevy Volt, Ford Fusion and Chrysler Pacifica Hybrid. New steel fuel tanks are alsoexpected to be seen in next generation vehicles coming from some import manufacturers very soon.

Steel Performs Better for Evaporative Emissions

Steel fuel tanks offer new design flexibility and have cost, mass and capacity advantages, ideal for meeting hybrid design goals; Zero evaporative emissions with sealed high-pressure/vacuum architecture, requiring high strength and stiffness at all working temperatures while also meeting stringent NVH targets. These tanks perform better with regard to ultra-low evaporative emissions because of steel’s inherent impermeability to hydrocarbons. Further, steel is compatible with all fuel types, including gasoline, alcohol, diesel, and bio-diesel, and is ideal for meeting low evaporative emission requirements. This makes steel the best choice for meeting evaporative emissions targets by preventing permeation better than plastic tanks.Plus, these increasing environmental restrictions have significantly increased the manufacturing cost of producing ultra-low evaporative emission plastic tanks.

Design Flexibility, Manufacturability, and Capacity

Today’s highly formable steels and improved manufacturing processes, coupled with advancements in design optimization not possible a decade ago, make steel fuel tanks superior to plastic in terms of cost, mass, fuel volume, and dimensional stability, especially in hybrid applications. Packaging space available for fuel tanks has become increasingly restricted and complex. Steel has the advantage of utilizing this space more efficiently compared with plastic tanks, and complex shaped tanks can be readily manufactured by conventional stamping processes.

In a design feasibility study, the Strategic Alliance for Steel Fuel Tanks (SASFT) showed how compared to a baseline plastic saddle tank, a similar solution could be reproduced using steel with 4% increased fuel capacity,demonstrating clear benefits for steel over HDPE alternatives. Other benefits include emitting fewer greenhouse gases and consuming less energy at comparable or lower cost while improving the vehicle’s lifecycle emissions. Steel tanks are also corrosion resistant, meeting 15-year/150,000-milelifespan minimums, are less susceptible to penetration, and are able to withstand high temperatures considerably better than their plastic counterparts.

Recyclability

Finally, end-of-life recyclability strongly favors steel through an existing infrastructure of dismantling, shredding and re-melting at steel mills. Steel is the most recycled automotive material in the vehicle, with nearly 100% recovery and no end-of-life vehicle costs.While nearly 15 million tons of steel are recycled annually from automobiles, there remains no fully-developed recycling infrastructure for plastic fuel tanks andtheir absorption of gasoline further complicates their end-of-life treatment. Thus, plastic tanks must be either landfilled or incinerated at a significant cost and environmental impact.

For more information about the clear benefits of steel fuel tanks, visit www.sasft.org or contact Michael A. White – SASFT Project Manager at the Steel Market Development Institute, 248.945.4779 | mwhite@steel.org.

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