Coatings continued steel sheet

Nowadays, however, zinc-coated steel sheets, either continuously galvanised or electroplated, are often used as a basis material for overcoating with plastic materials or paints. The coatings are usually applied continuously and have a range of uses both externally and internally. Many surface finishes are obtainable, e.g. plain or embossed, and in an extensive range of colours, to suit almost any requirement . 

Vast amounts of continuously galvanised steel sheets are produced, and unless they are painted or otherwise coated, their life depends on the thickness of the galvanising and the service environment in which they are used. Similarly in the case of steel sheets coated with aluminium or aluminium-zinc alloys, their performance is dictated by their coating thickness (see Section 13.4). A problem often associated with such material is corrosion at the cut edges. From work carried out by BISRA and others it has been shown that providing the bare steel edge is less than 3 mm in width, the amount of corrosion is minimal and the life of the sheet is not adversely... 

For applications such as cladding fire-rated bulkheads and doors in ships and other vessels decor papers have been bonded directly to thin steel sheet. However, for these purposes steel coated with PVC and thin continuous laminate bonded to steel now are used more commonly. 

Hot dipping is carried out by immersing the metal on which the coating is to be applied, usually steel, in a bath of the molten metal that is to constitute the coating, most commonly zinc, but also aluminum and aluminum-zinc alloys. Hot dipping can be either a continuous process, as in galvanizing steel sheet, or a batch process— for example, galvanizing fabricated parts, nuts, bolts, and fasteners [1]. 

Steel sheet, strip, wire, and tube are all galvanized in the semifabricated state. Fabrication practice is the same as with ungalvanized material, and the only additional requirement is to restore the coating (see later) to areas from which it has been removed by, for example, machining during fabrication. Similar comments apply to continuously electroplated sheet, strip, and wire. The other zinc coatings are normally applied after fabrication. 

Anon. (1988). Continuous Hot-Dip 55% Aluminium-Zinc Coated Steel Sheet. Technical brochure, BIEC International, Siegen, Germany, 48 pp. 

Skenazi, A. F., Davin, A., Coutsouradis, D., and Goodwin, F. E. (1985). The influence of alloying elements in zinc-aluminium baths for continuous hot dip galvanizing. 1st Int. Conf. on Zinc Coated Steel Sheet, ZDA, London, pp. OA/1-5. 

AppUcation of PVD coatings to coils of steel sheet in a continuous process was studied extensively in the United States during the 1970s, but the process was found to be more costly relative to other coating methods, such as electroplating and hot dipping. More recently, efforts are underway in Japan and Europe to further develop such a process. 

Aluminum coated Steel sheet is produced in coil form by continuous hot dipping in a molten eduminum bath. The resultant coating consists of an iron-aluminum intermetallic layer and an aluminum overlay with a total thickness of 20-40 pm. The product, referred to as Type 2 aluminum coated, is used mostly for light construction, e.g., metal buildings, sUos, and highway culvert. 

TVnother continuously coated steel sheet product. Type 1 aluminum-coated, is made by hot dipping in a molten bath of aluminum containing 5-11 % silicon [79]. Typ>e 1 coatings are thinner, typically 10-20 pm, and are more foimable than T5rpe 2 coatings. This product is widely used in high-temperature applications (up to 675°C), particularly for automobile tailpipes and mufflers. 

Although not truly metalhc, a type of chromium coating is continuously applied to steel sheet in the production of tin-free" steel (TFS). TFS was developed as an alternative to tinplate for the container industry. A mixture of chromium... 

Produced by hot-dip coating cold-rolled sheet steel on continuous lines. It provides a material with the superior strength of steel and the surface properties of aluminum. 

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