Witterungsbeständiger Metallwerkstoff und Verfahren zu seiner Herstellung

摘要

A method of manufacturing a composite body comprising a stainless steel substrate provided with a tin based alloy coating comprises pickling a stainless steel substrate so as to provide the substrate with a surface substantially free of chromium oxide; and hotdip coating said surface with a tin based alloy so as to have an alloy coating of a thickness in the range of 7 x 10<-3>mm to 2.5mm. The pickling solution may be hydrofluoric acid, sulphuric acid, nitric acid, hydrochloric acid, phosphoric acid or isobromic acid. The surface may be treated with an abrasive and/or absorbent material prior to pickling; or the pickled surface may be treated with a deoxidizing agent, eg ZnCl2. The hot-dip coating may be carried out in a tinning vat comprising a flux zone containing ZnCl2 and NH4Cl and an alloy coating zone. Spray jets 84, as illustrated in Fig 2 are provided proximal an exit region of the coating zone to spray molten alloy onto one or more rollers 82 so as to ensure substantially complete coating of the stainless steel substrate by the molten alloy. A protective skin of palm oil may be applied after the hot-dipping. An asphalt-based or petroleum-based paint as a weathering agent may be subsequently applied and this composite body used as a roofing material having water-proofing properties.