The patent badge is an abbreviated version of the USPTO patent document. The patent badge does contain a link to the full patent document.
The patent badge is an abbreviated version of the USPTO patent document. The patent badge covers the following: Patent number, Date patent was issued, Date patent was filed, Title of the patent, Applicant, Inventor, Assignee, Attorney firm, Primary examiner, Assistant examiner, CPCs, and Abstract. The patent badge does contain a link to the full patent document (in Adobe Acrobat format, aka pdf). To download or print any patent click here.
Patent No.:
Date of Patent:
May. 05, 1981
Filed:
Nov. 21, 1979
Gebhard Wagner, Odenthal, DE;
Werner Joseph, Cologne, DE;
Bayer Aktiengesellschaft, Leverkusen, DE;
Abstract
In a two-layer enamelling process in which the ground coat and surface coat powders are electrostatically applied to metallic substrates and subsequently baked together, the improvement which comprises employing a ground coat powder having an electrical resistivity of about 10.sup.10 to 10.sup.14 ohm. cm and a surface coat powder having an electrical resistivity of about 10.sup.14 to 10.sup.16 ohm. cm. Advantageously the surface tension of the ground coat amounts to at least about 0.280 N/m and the surface tension of the surface coat to at most about 0.260 N/m, the difference between the surface tensions of the ground coat and surface amounts to at least about 0.050 N/m, the ground coat powder has an electrical resistivity 10.sup.12 to 10.sup.14 ohm. cm and at least about 10.sup.2 ohm. cm lower than that of the surface coat powder, the ground coat powder contains at least one of an alkaline earth metal, zinc, manganese or iron oxide in a total concentration of about 20 to 30% by weight, the zinc oxide content not exceeding about 12% by weight and the manganese oxide plus iron oxide content not exceeding about 9% by weight, about 3 to 5% by weight of finely divided iron oxide is added to the ground coat powder before adjustment of its electrical resistivity, and the ground coat powder is applied in such a quantity that, after baking, the ground coat has a layer thickness of about 0.02 to 0.03 mm.