The invention relates to coating formulations (B) which can be hardened to form coatings having a pencil hardness according to ISO 15184 of at least HB. Said formulations contain prepolymers (A) having alkoxysilane functions of general formula (6) --X--CH.sub.2--Si(OR)3-.sub.xR'.sub.x, wherein R represents hydrogen, an alkyl, cycloalkyl or aryl radical respectively having between 1 and 6 atoms, and the carbon chain can be broken by non-adjacent oxygen, sulphur or NR'' groups; R' represents an alkyl, cycloalkyl, aryl or arylalkyl radical respectively having between 1 and 12 C atoms, and the carbon chain can be broken by non-adjacent oxygen, sulphur or NR'' groups; R'' represents hydrogen, an alkyl, cycloalkyl, aryl, aminoalkyl, or aspartate acid ester radical; X represents oxygen, sulphur or a group of general formula (20) --O--CO--NR''--; and x represents 0 or 1.