BENEFITS OF STEEL FUEL TANKS

Steel fuel tanks have been widely used since the early days of the automobile's development. Thus, a strong history of performance, safety, low cost, and recyclability of steel fuel tanks has been established. Despite the growth of plastic fuel tanks in recent years, steel tanks are better suited to today's demanding environmental and engineering performance requirements.

Attractive Cost

• As the environmental restrictions on evaporative emissions increase, the manufacturing costs for producing ultra-low evaporative emission plastic tanks are increasing. In contrast, steel fuel tanks continue to be an attractive means of achieving emission targets at affordable cost. The worldwide steel industry has developed a variety of steel systems to meet the specific approaches favored by automakers (e.g., pre-painted, post-painted and bare steels). These advanced systems are durable and have improved formability and weldability.

Technical Assistance and Support to Automakers

• The global steel tank manufacturers have the ability to assist automakers in tank design, meeting specific performance needs and in assurance testing. Furthermore, the SASFT network of steel fuel tank manufacturers, equipment suppliers and steel companies can be utilized to facilitate development and application of new technologies.

Ultra-Low Evaporative Emissions Capability

• Evaporation of gasoline from automotive fuel systems is a major contributor toward air pollution and its attendant health hazards. This has led national and regional government agencies to restrict the amount of automobile evaporative emissions. Steel's inherent impermeability is ideal for limiting evaporative emissions. In fact, steel is now the material of choice for meeting the California Air Resources Board's (CARB) Partial Zero Emission Vehicle (PZEV) requirements. In the 2005 model year, 29 PZEV-certified vehicles use steel fuel tanks. In contrast, plastic fuel tanks are still struggling to demonstrate PZEV capability.

Recyclability

• Steel fuel tanks have been, and continue to be, fully recyclable through an existing infrastructure of dismantling, shredding and re-melting at steel mills. The steel recycling infrastructure is a profitable industry and, hence, no end-of-life vehicle costs are incurred by vehicle makers or consumers. In contrast, the absorption of gasoline in the walls of plastic tanks complicates their end-of-life treatment and no fully developed recycling infrastructure is in place anywhere in the world. Plastic tanks must be either landfilled or incinerated at a significant cost. Landfilling depletes valuable land resources and together with incineration creates additional environmental concern for toxins in the soil or air.

Design Flexibility

• Newly developed steels and steel systems have improved formability. As a result, complex shaped tanks can be readily manufactured by conventional stamping processes. Many 'saddle shaped' tanks are routinely produced today from steel. A recent SASFT design feasibility study showed that a current in-production plastic saddle tank could be produced from steel with 4% increased fuel capacity and a proportional increase in weight.

Durability

• In addition to meeting ultra-low emission standards, CARB stipulates that fuel systems shall meet a 15-year or 150,000 mile life. SASFT, in an extensive two-year test program, has demonstrated that 10 steel systems will meet both external corrosion resistance to road environments and internal corrosion resistance to aggressive fuels.

Optimizing Fuel Tank Capacity by Efficient Use of Engineering Space

• The engineering space that accommodates a fuel tank is becoming increasingly restricted and complex. Steel has the advantage of utilizing this space more efficiently compared with plastic tanks, where allowances must be made for thermal expansion and warpage. Additionally, the variable wall thickness of plastic tanks (ranging from 2 to 15 mm) restricts the fuel volume compared with a constant thickness (typically <1 mm) steel shell. New joining techniques are emerging allowing a reduced flange, enabling the steel shell to be expanded further. It is estimated that fuel capacity increases up to 10% or more can be realized by reducing or eliminating the weld flange.

Safety

• Vehicles equipped with steel tanks have demonstrated the ability to meet all current and future government regulations and requirements for fuel system integrity after front, rear and side impacts.

IN SUMMARY...

• Best material for PZEV applications thanks to inherent impermeability to hydrocarbons.
• Cost competitive with current co-extruded blow-molded plastic fuel tanks.
• Corrosion resistant to road environments (15-year life minimum or 150,000 miles).
• Compatible with all fuels.
• Good design flexibility (complex shape/saddle tank capability).
• Readily manufacturable by well-proven, conventional, low cost, widely available processes.
• Over 100 years of proven performance and safety.
• 100% recyclable. Nearly 15 millions tons of steel are recycled annually from automobiles.

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