Use of 2-component coating systems, comprising: i) at least one prepolymer containing free isocyanate groups, obtainable by reaction of aliphatic di- or polyisocyanates with at least one polyoxyalkylene polyol obtainable by alkoxylation of hydroxy-functional starter molecules with a an average hydroxy functionality of 1.5 to 3 and an equivalent weight of at least 400 g/mol, and ii) at least one amino-functional polyaspartic acid ester of the general formula where X represents an n-valent organic radical which is obtained by removal of all amino groups from a polyamine, selected from the group consisting of 1-amino-3,3,5-trimethyl-5-aminomethyl-cyclohexane, 2,4-hexahydrotoluylenediamine, 2,6-hexahydrotoluylenediamine, 2,4'-diamino-dicyclohexylmethane, 4,4'-diamino-dicyclohexylmethane, 3,3'-dimethyl-4,4'-diamino-dicyclohexymethane, 2,4,4'-triamino-5-methyl-dicyclohexylmethane or mixtures thereof, R1 and R2 independently of one another represent a methyl or an ethyl group and n represents an integer of at least 2, characterized in that the at least one prepolymer containing free isocyanate groups has a content of aliphatically-bound NCO groups of 12.5 to 17% by weight, and wherein it is used as a primer for mineral substrates. i) at least one prepolymer containing free isocyanate groups, obtainable by reaction of aliphatic di- or polyisocyanates with at least one polyoxyalkylene polyol obtainable by alkoxylation of hydroxy-functional starter molecules with a an average hydroxy functionality of 1.5 to 3 and an equivalent weight of at least 400 g/mol, and ii) at least one amino-functional polyaspartic acid ester of the general formula where X represents an n-valent organic radical which is obtained by removal of all amino groups from a polyamine, selected from the group consisting of 1-amino-3,3,5-trimethyl-5-aminomethyl-cyclohexane, 2,4-hexahydrotoluylenediamine, 2,6-hexahydrotoluylenediamine, 2,4'-diamino-dicyclohexylmethane, 4,4'-diamino-dicyclohexylmethane, 3,3'-dimethyl-4,4'-diamino-dicyclohexymethane, 2,4,4'-triamino-5-methyl-dicyclohexylmethane or mixtures thereof, R1 and R2 independently of one another represent a methyl or an ethyl group and n represents an integer of at least 2, characterized in that the at least one prepolymer containing free isocyanate groups has a content of aliphatically-bound NCO groups of 12.5 to 17% by weight, and wherein it is used as a primer for mineral substrates. where X represents an n-valent organic radical which is obtained by removal of all amino groups from a polyamine, selected from the group consisting of 1-amino-3,3,5-trimethyl-5-aminomethyl-cyclohexane, 2,4-hexahydrotoluylenediamine, 2,6-hexahydrotoluylenediamine, 2,4'-diamino-dicyclohexylmethane, 4,4'-diamino-dicyclohexylmethane, 3,3'-dimethyl-4,4'-diamino-dicyclohexymethane, 2,4,4'-triamino-5-methyl-dicyclohexylmethane or mixtures thereof, R1 and R2 independently of one another represent a methyl or an ethyl group and n represents an integer of at least 2, characterized in that the at least one prepolymer containing free isocyanate groups has a content of aliphatically-bound NCO groups of 12.5 to 17% by weight, and wherein it is used as a primer for mineral substrates.