Use of compositions comprising a) at least one azole and b) at least one amidoalkylamine of the formula (I), a salt and/or acid addition compound thereof, in which R1 represents optionally substituted C1-C40-alkyl or C2-C40-alkenyl, R2, R3 and R4 independently of one another represent hydrogen or C1-C8-alkyl and n represents an integer from 1 to 6 for protecting industrial materials against attack and/or destruction by microorganisms.