The results of researches of sorption processes of surface layers of components of sand moulds covered by protective coatings are

presented in the hereby paper. Investigations comprised various types of sand grains of moulding sands with furan resin: silica sand,

reclaimed sand and calcined in temperature of 700oC silica sand. Two kinds of alcoholic protective coatings were used – zirconium and

zirconium – graphite. Tests were performed under condition of a constant temperature within the range 30 – 35oC and high relative air

humidity 75 - 80%. To analyze the role of sand grains in sorption processes quantitavie moisture sorption with use of gravimetric method

and ultrasonic method were used in measurements. The tendency to moisture sorption of surface layers of sand moulds according to the

different kinds of sand grains was specified. The effectiveness of protective action of coatings from moisture sorption was analyzed as

well.

Knowledge of the role of sand grains from the viewpoint of capacity for moisture sorption is important due to the surface casting defects

occurrence. In particular, that are defects of a gaseous origin caused by too high moisture content of moulds, especially in surface layers.