Change in environmental legislation and innovative forming techniques open up new perspectives

More stringent environmental laws and new forming processes have opened up new perspectives for steel in the manufacture of fuel tanks. Having withstood fierce competition from plastic since the early seventies, steel is now set to become the material of choice again for fuel tanks.

Traditionally, the advantages of plastic lie in its flexible forming properties. Blow-molded plastic fuel tanks can be produced in very complex shapes to fit into even the smallest corner, making optimum use of the space available. The disadvantage of plastic is that it lets pollutants caused by evaporation of the fuel escape. At present conventional plastic fuel tanks allow more than two grams of hydrocarbon per day to escape through the tank walls alone. Emissions of this kind will no longer be permissible in future.

In California, for example, the law already requires carmakers to reduce hydrocarbon emissions from the entire vehicle to a maximum of two grams. From 2004 this limit will be lowered further. Europe will follow suit. All of which is good news for steel.

Steel already meets all the requirements of the relevant future legislation. Steel tanks emit zero hydrocarbon and - unlike plastic - steel is virtually one hundred percent recyclable. Furthermore, in recent years new forming techniques with liquid forming agents have been developed such as parallel-plate hydroforming and hydromechanical sheet forming, which permit tanks to be produced in shapes as complex as those of plastic tanks. The further development of steel materials, in particular the improvement of the forming properties of IF (Interstitial Free) carbon steels, has also contributed toward expanding forming potential.

At Hanover Fair ThyssenKrupp Steel is presenting two examples of environmentally friendly steel fuel tanks, one made of hot-dip aluminized sheet and the other of NIROSTA® 4301 stainless. The Duisburg-based steel producer has over 40 years experience with tanks made of coated sheet. Fuel tanks made of hot-dip aluminized sheet currently feature in the majority of models produced by DaimlerChrysler AG. For the future it is planned to further improve the corrosion resistance of the sheet with an organic coating.

The NIROSTA® tank is a new application for stainless steel, with the combined advantages of good forming properties and outstanding corrosion resistance. Its long service life makes the material an attractive alternative in particular in view of the 15-year warranty periods now required. Tanks made of NIROSTA® are currently being tested by a number of national and international automobile manufacturers.

For further reference: ThyssenKrupp AG, Trade Press, Bernd Overmaat Tel: +49-211-824-36012, Fax: +49-211-824-36035 e-mail: overmaat@tk.thyssenkrupp.com