What Is Coating
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The "paint" we usually refer to is just one type of coating. Coating refers to a class of liquid or solid materials that can be applied to the surface of an object and form a film under certain conditions to play a protective, decorative, or other special functional role (such as insulation, rust prevention, mildew resistance, heat resistance, etc.). In the early days, most coatings used vegetable oil as the main raw material, so they were also called "paints". Now, synthetic resins have mostly or completely replaced vegetable oil, hence the name "coatings".
Generally, for products of oil-based and paint-based coatings, the character "qi" (paint) is often used in the naming of specific coating varieties to represent "coating", such as ready-mixed paint, primer, topcoat, etc. After long-term development, there are many methods for classifying its products. Coatings have a particularly wide variety of types, and there are also many classification methods:
① Classified by coating form (powder, liquid);
② Classified by film-forming mechanism (conversion type, non-conversion type);
③ Classified by application method (brushing, rolling, spraying, dipping, flowing, electrophoresis);
④ Classified by drying method (room-temperature drying, baking drying, moisture curing, steam curing, radiant energy curing);
⑤ Classified by application layer (primer, intermediate coat, topcoat, putty, etc.);
⑥ Classified by film appearance (varnish, pigmented paint; matte, flat matte, semi-matte, high gloss; hammer finish paint, embossed paint, etc.);
⑦ Classified by application object (automotive paint, marine paint, container paint, aircraft paint, home appliance paint, etc.). Marine coatings can be further classified into anti-rust coatings, anti-corrosion coatings, anti-fouling coatings, weather-resistant coatings, heat-resistant coatings, as well as ship bottom paint, hull paint, deck paint, marking paint, oil tank paint, battery tank paint, ballast water tank coating, ammunition tank coating, living cabin coating and other special functional coatings according to the characteristics of the application parts and environment;
⑧ Classified by film performance (anti-corrosion paint, insulating paint, conductive paint, heat-resistant paint, etc.);
⑨ Classified by film-forming substance (alkyd, epoxy, chlorinated rubber, acrylic, polyurethane, ethylene, etc.).
Each of the above classification methods has its own characteristics, but none of them can cover all the specific properties of coatings. Therefore, there is no unified classification method in the world.
China's national standard GB 2705-92 adopts a classification method based on the film-forming substances in coatings. Coatings usually consist of base material (resin, adhesive), pigment, filler, solvent and a small amount of functional additives, etc. They can be divided into 17 categories according to the type of base material; according to performance characteristics, they can be divided into organic coatings, inorganic coatings, solvent-based coatings, solvent-free coatings, water-based coatings, powder coatings, high-solid coatings and thick-film coatings, etc.; according to their functional characteristics, they can be further divided into enamel paint, pigmented paint, varnish, ready-mixed paint, primer, topcoat and intermediate coat, etc. The finished products include formwork paint, interior and exterior wall emulsion paint, fire-resistant emulsion paint, etc.
