Several vehicle manufacturers around the globe have introduced aluminium for car body construction for many years. So far, the application of aluminium, with very few exceptions, is limited to the substitution of steel closure sheets for top models. All-aluminium vehicles have also been put on the road some ten years ago. The production numbers of these all-aluminium cars, however, were very low in most cases. Most recently, multifaceted and ambious plans have been developed by the car industry to either introduce aluminium for the first time or to greatly increase its amount in the car. The amount of aluminium forseen for future vehicles ranges from 10 % for an aluminium closure sheet, i.e. hood, through 30 - 50 % for all skin panels to 100 % in several cases. The use of aluminium for car body construction makes it necessary to adapt production techniques to aluminium in the press, body and paint shops. One of the most cost driving process steps is the additional chemical treatment prior to welding and bonding conducted either in-house or by job coaters. One of the major demands of the automotive industry was to develop new techniques which allows the shifting of this extra treatment upstream to the coil line. The surface preparation of multi-metal car bodies for painting by fluoride-modified low-zinc phosphating is state-of-the-art today. Although all-aluminium vehicles can also be processed through phosphating to a certain extent, new chrome-free pretreatment techniques are needed for the processing of all-aluminium vehicles at higher production rates. Processes have been developed which allow the pretreatment prior to welding and adhesive bonding to be shifted upstream to the aluminium coil producer. This eliminates investment and operating costs for the deoxidation/passivation treatments of the stamped parts in the car assembly plant. The technology of phosphating for aluminium, steel and zinc-coated steel is reviewed including new developments as nickel- and nitride-free processes. Chrome-free processes for treating all-aluminium vehicles have also been developed most recently. The processes and the status of market introduction will be discussed in detail.
Chemical pretreatment of multi-metal and all-aluminium car bodies
Chemische Vorbehandlung von Karosseriebauteilen aus mehreren Metallen oder aus Aluminium
2000
11 Seiten, 14 Bilder
Conference paper
English
Automobilindustrie , Karosserie , Aluminiummagnesiumlegierung , Aluminiummagnesiumsiliciumlegierung , Aluminiumsiliciumlegierung , Aluminiumkupfermagnesiumlegierung , chemische Vorbehandlung , Phosphatieren , Entwicklungsstand , Desoxidation , Passivierung , Marktentwicklung , Umweltverträglichkeit , Kostenanalyse , Stahl , Zinkbeschichtung
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