Protective coatings are used to protect the metal and to isolate it from aggressive environment. Metal protective coatings can be of metallic and non-metallic structure.
Metallic protective coatings
Metallic protective coatings are applied to surface (metal, glass, ceramic, plastic and others) in order to protect it from corrosion, to give hardness, conductivity, wearability and also to decorate its visual environment.
Corrosion protection with metallic coatings is performed in the following ways:
– metal spray coating – spraying molten metal to the work surface with air stream;
– hot-dip protective coating procedure – metal ware dipping into a bath with molten metal;
– galvanic (electrolytic) – metal or aqueous solution of its salting alloy deposition to the ware surface, constantly conducting it through electrolyte current electricity;
– cladding (thermomecanical) – surface application of the main metal – another one, more resistant to aggressive environment, using casting, rolling or deformed cladding (pressing, hammering);
– diffusive – the point of this method is in metal coating penetration into the surface layer of the main metal affected by high temperature.
Non-metallic protective coatings
Non-metallic protective coatings are used to isolate metal ware, to protect it from the humidity, also to give it a pleasing aspect. Non-metallic protective coatings can be subdivided into paint-and-lacquer, polymer, rubber, silicate enamel coatings.
Paint-and-lacquer protective coating
Paint-and-lacquer protective coatings are widely spread and are used more often. The coating composition includes film-forming materials, fillers, colorants, plasticizers, solvents, accelerators. Such coating doesn’t only protect the ware well in different environments, but also gives it a pleasant view.
Polymer protective coatings
Polymer protective coatings are applied to the ware surface in the form of hot resin in order to protect it from the environment. The resin coating can be performed by dipping, hot and fluidized bed coating, also by a simple brush.
Rubber protective coatings
Rubber protective coating can be performed by rubber and ebonite for different storages, pipe-lines, cisterns, chemical equipments, containers for transportation and storing of chemical agents. This metal protective coating can be formed by soft or hard rubber.
Silicate enamel protective coatings
Silicate enamel protective coatings are used for ware that are operated with high temperatures, pressures, in very aggressive, chemical active environments. The enamel protective coating can be operated in two ways: dry (applied in the form of powder) or wet (slurry).