Pain-and-lacquer coatings (oil and enamel paints, also nitroenamels) are used for protective and decorative purposes. Oil paints made of oils and drying oil, they are produced in the form of paste. They are dissolved with drying oil to working viscosity before the application and apply it to the surface with brush or air compressor. Oil paint coatings have thin luster. Enamel paints are prepared on lacquers: they spill oleoresin, ethanilic and nitrocellulose enamels prepared on cellulose ester lacquers. Enamels are produced ready-to-use. Oleoresin enamels are applied with brush or air compressor, but nitrocellulose enamels — mainly with air compressor, because they dry out fast. Enamel coatings differ for good luster and enhanced strength, temperature shifting resistant from -40 to +60 °С.
Coating selection standards
When selecting coating it is important to take into account:
- the element purpose;
- the coating purpose;
- the detail and coating operation conditions;
- the detail materials;
- the metal coating and application operating procedure environmental disposal;
- the metal and metallic/non-metallic coatings contact acceptability;
- the economic feasibility.
There exist a number of protective decorative coatings for metals types. It can be: zinc, cadmic, chromium coatings.
Zinc coating is an anodic one in relation to black metals, it protects steel from corrosion in an electrochemical way at temperatures below 70 °С, at higher temperatures – in a mechanic way. The coating has rigid adhesion to the main metal, low chafing resistance and enhanced embrittlement at temperatures higher 250 °С and lower 70 °С; the frosting coating stands bending, expansion.
Cadmic coating is an anodic one, it protects steal from corrosion in the atmosphere and sea water in an electrochemical way; in fresh water – in a mechanic way. For corrosion resistance hardening the cadmic coating is chromized and phosphatized. The chromatizing also improves the coating decorative appearance. The chromate film is mechanically incompetent. The corrosion speed in industrial atmosphere is 1,5 – 2 times more than zinc coating has.
Chromium coating is a cathodic protective decorative coating for metals in relation to the steel, aluminum and zinc alloys, it provides corrosion protection and improves decorative appearance. Matte chromium coating has low hardness and wearability, a little of sponginess. The coating protects from corrosion preserving the decorating appearance. Chromium coatings application to figurine-shaped detections is difficult because of low chromium electrolytes diffusing power.