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May 24, 2008

Metal with Plastic Coating

Protecting metal from corrode effect have used with many way, using anodizing for aluminum metal, electroplating for steel and other metal coated with other stabilize metal and endure from corrosion.

Metal coating with plastic may well be the constructional materials of the future. Already large quantities of strip steel are laminated with a performed plastic film, using adhesives. One such product is marketed under the trade name Stelvitite. Plastic is extruded around a metal core for curtain rails. These processes, however, must be considered as methods of manufacture rather than of surface treatment.

Plastics do not melt to a limpid on heating and cannot be applied in a liquid form. As their name implies, on heating they become plastic and sticky. A very successful method of coating metal, especially wire work goods, e.g. racks and light structures, chain-link fencing and grills, with polyvinyl chloride or similar thermoplastic material is as follows. The plastic is finely powdered and is placed is a deep box; a perforated bottom plate permits air to be blown up through the plastic powder. This maintains it in a mobile or fluidized condition. The metal articles are preheated to about 150oC and the plunged into the seething mass of powder. This particles which touch the hot metal become softened and sticky; they adhere to it. After withdrawal the metal part is re-heated for a short time to allow the individual plastic particles to coalesce and draw up to a smooth coating by surface-tension forces. The resultant coating is about 0.005 in thick.

Alternatively, colloidal dispersions of partially polymerized in plasticizer, or of completely polymerized thermoplastic material in the minimum of water, consisting of very thick creamy liquids may be used for coating metal objects by dipping. These are called plastizols or organosols. The solidification of the plastic is accomplished by subsequent heating.