The protective properties of I-40 industrial and M-11 motor oils containing N-substituted 2,4-diamino-6-alkylthio- and 2-amino-4,6-dialkylthio-sym-triazones as corrosion inhibitors are investigated. It is shown that some of these compounds are more effective than the industrial corrosion inhibitor Penazolin 10-16 - a mixture of 1,2-disubstituted imidazolines obtained by condensation of C-10-C-16 synthetic fatty acids (SFA) with polyethylenepolyamines.