| 摘要 |
The present invention discloses a method to form a coating of chemical conversion over substrates of ferrous metal, using chemical solutions for the coating and the articles coated with the same. When modifying and combining the characteristics of two existent coating techniques, but to date not related, a hybrid conversion coating is formed. Specifically, an intermediate coating enhanced with molecular iron/oxygen, such as a dicarboxylate or phosphate, to a ferrous substrate by means of a first oxidation. The intermediate coating preconditions the substrate to form a surface rich in molecular iron and oxygen in an easy and accessible way for an ulterior reaction. This oxidation procedure is followed by a coloration procedure employing a hot oxidation solution (approximately 48.4 to 103.4°C (120 to 220°) which contains an alkali metal hydroxide, an alkali metal nitrate, an alkali metal nitrite or their mixtures, reacting with the iron and oxygen enhanced intermediate coating to form m agnetite, (Fe3O4). The result is the formation of a brown or black finishing under more favorable, benign and safe conditions than the ones previously observed with the conventional processes of caustic blackening, as consequence of the chemical reaction between the intermediate coating and the solution of the second oxidation. When sealed with an appropriate preventive upper layer of the oxidation, the final result is an attractive ultra-thin protective finishing applied through a simple immersion technique. The finishing is a coating of final protection over a fabricated metal article and likewise provides a grade of lubricity to help assembling the sliding surfaces or provides an anti-scratch protection. The finishing also provides an adherent base for paint finishings.
|
