**2. Characteristics and division**

Ceramic coating includes materials with a composition set in advance, which refractoriness and other properties prevent reactions on the mould-metal contact surface from happening. There are three basic classes of coatings for moulds and cores from the aspect of the basic ingredient as follows:


Graphite coatings are agents containing graphite or similar materials as a refractory filler. Ceramic coatings are agents containing fine milled ceramic materials such as zircon, quartz, chamotte, magnesite, olivine, chromite, talc, mica, cordierite and alike as a refractory filler. The coatings not changing casting surface properties are classified into the group of passive coatings. In terms of physical properties, there are the following coating types:


Liquid and semi-liquid coatings are used for either dry or semi-dry moulds, while powders are used for wet moulds. Growth tendency regarding quality and complexity of casting production, constant requirements for as high quality casting surface as possible and for production cost reduction impose the need to improve the production of foundry coatings and thereby to widen their function range. Nowadays, so called active coatings are increasingly used; their role, different to the one of protective (passive) coatings, is reflected in the change of properties in the surface layer of castings. Active ingredients of this type of coating penetrate into inner metal layers either by merging or diffusion. It has a different effect on casting quality, such as hard structure formation (spots on a casting which are in contact with the coatings containing tellurium, bismuth), cementation (presence of carbon in coatings) or prevention of appearance of scratches on castings (iron (III) oxide, (Fe2O3) (Gorni & Marcinkowski 1977, Monroe 1994, Tsai & Chem 1988).

There are different divisions of coatings, often according to the type of casted metal (for non-ferrous metals, steel, cast iron), and according to the chemical character (acid, base, neutral). The choices of coatings are made based on the type of mould and core either. The method of mould production out of different mould blends with different systems to bind the sand grains (cold mould casting, hot mould casting, CO2 procedure, expendable pattern casting, shell process) influence the choice of the type of coating. For moulds and cores

types of castings and types of alloys. At the same time, all relevant quality indicators and economy indicators for the casting production should be monitored. Coating properties are strictly defined by standards; therefore, it is very important to make the right choice of coating, as well as its preparation and application in concrete foundry working conditions

Ceramic coating includes materials with a composition set in advance, which refractoriness and other properties prevent reactions on the mould-metal contact surface from happening. There are three basic classes of coatings for moulds and cores from the aspect of the basic

The class based on a mixture of carbon and highly refractory ingredients, (blended

Graphite coatings are agents containing graphite or similar materials as a refractory filler. Ceramic coatings are agents containing fine milled ceramic materials such as zircon, quartz, chamotte, magnesite, olivine, chromite, talc, mica, cordierite and alike as a refractory filler. The coatings not changing casting surface properties are classified into the group of passive

 The class based on graphite or some other sort of carbon, (graphite coatings), The class based on highly refractory materials, (ceramic coatings), and

coatings. In terms of physical properties, there are the following coating types:

Semi-liquid coatings (pastes) based on organic solvents;

(Gorni & Marcinkowski 1977, Monroe 1994, Tsai & Chem 1988).

Liquid coatings based on organic solvents, such as isopropanol, ethanol and alike;

Liquid and semi-liquid coatings are used for either dry or semi-dry moulds, while powders are used for wet moulds. Growth tendency regarding quality and complexity of casting production, constant requirements for as high quality casting surface as possible and for production cost reduction impose the need to improve the production of foundry coatings and thereby to widen their function range. Nowadays, so called active coatings are increasingly used; their role, different to the one of protective (passive) coatings, is reflected in the change of properties in the surface layer of castings. Active ingredients of this type of coating penetrate into inner metal layers either by merging or diffusion. It has a different effect on casting quality, such as hard structure formation (spots on a casting which are in contact with the coatings containing tellurium, bismuth), cementation (presence of carbon in coatings) or prevention of appearance of scratches on castings (iron (III) oxide, (Fe2O3)

There are different divisions of coatings, often according to the type of casted metal (for non-ferrous metals, steel, cast iron), and according to the chemical character (acid, base, neutral). The choices of coatings are made based on the type of mould and core either. The method of mould production out of different mould blends with different systems to bind the sand grains (cold mould casting, hot mould casting, CO2 procedure, expendable pattern casting, shell process) influence the choice of the type of coating. For moulds and cores

(Cho 1989, Cibrik 1977, Brome 1988, Davies 1996, Josipović et al. 1994).

**2. Characteristics and division** 

ingredient as follows:

coatings).

Liquid coatings with water;

Dry (powder) coatings.

Semi-liquid coatings (pastes) with water;

made out of the quartz sand mixed with binding agent, one kind of ceramic coatings is used, while the other kind of ceramic coatings is used for metal moulds and metal cores. It includes the choice of a refractory filler, binding agent, additives and solvents in accordance with notions and processes carried out on the mould-coating-liquid metal contact surface during the phase of inflow, cool down and solidification of castings (Tomović 1990).
