Compositions containing heterocyclic corrosion inhibitors

A composition which comprises (A) an aqueous or non-aqueous coating composition suitable for preparing a surface coating which is a paint, and (B) an effective corrosion-inhibiting amount of a compound of formula II ##STR45## in which X is sulphur;

• R is each independently of one another hydrogen, alkyl, haloalkyl, alkoxy, alkylthio, alkylsulfonyl, cycloalkyl, phenyl, alkylphenyl, phenylalkyl, halogen, cyano, nitro, hydroxy, --COOH, --COOalkyl or a primary-, secondary- or tertiary-amino or carbamoyl group;
• n is 0 or 1;
• R.sup.1, R.sup.2, R.sup.3 and R.sup.4 are independently hydrogen, alkyl, hydroxyalkyl, haloalkyl, alkoxyalkyl, phenyl, phenyalkyl, said phenyl or said phenylalkyl substituted by one or two of halogen, of alkyl, of alkoxy, of carboxy or of hydroxy;
• carboxy, alkyl substituted by one, two or three of carboxy or of --COOZ;
• or --COOZ where
• Z is C.sub.1 -C.sub.18 -alkyl, said alkyl interrupted by one or more O or S atoms or by one or more NR.sup.o groups where R.sup.o is C.sub.1 -C.sub.18 -alkyl, C.sub.5 -C.sub.8 -cycloalkyl, phenyl, napthyl, C.sub.7 -C.sub.9 -phenylalkyl or C.sub.7 -C.sub.18 -alkylphenyl;
• or said alkyl substituted by --SH, by --COOR.sup.o, by --CONH.sub.2, by --CN or by halogen;
• C.sub.2 -C.sub.1 -hydroxyalkyl or said hydroxyalkyl interrupted by one or more NR.sup.o groups or by one or more oxygen atoms;
• C.sub.2 -C.sub.18 -alkenyl, C.sub.3 --C.sub.12 -cycloalkyl or said cycloalkyl substituted by C.sub.1 -C.sub.4 -alkyl, by --OH, by --SH, by --COOR.sup.o, by --CONH.sub.2, by --CN or by halogen;
• C.sub.7 -C.sub.9 -phenylalkyl, C.sub.7 -C.sub.18 -alkylphenyl, or C.sub.6 -C.sub.10 -aryl or said phenyl or said aryl substituted by C.sub.1 -C.sub.12 -alkoxy, by C.sub.1 -C.sub.12 -alkylthio, by --COOH, by --OH, by halogen or by nitro;
• or
• (B) is a compound of formula II where the moiety
• [--C(R.sup.1)(R.sup.3)].sub.n --CH(R.sup.2)(R.sup.4)
• contains a group of formula III or IIIa ##STR46## or where R.sup.1 and R.sup.2 or R.sup.1 and R.sup.3 together form a straight or branched alkylene, or said alkylene substituted by one or two --COOH or by one or two --COOZ;
• or where R.sup.1 and R.sup.2 form a direct bond;
• with the proviso that at least two of R.sup.1, R.sup.2, R.sup.3 and R.sup.4 must contain a carboxy group or a derivative thereof which is a --COOZ group or an anhydride of formula III or IIIa, and that at least one --COOH and one --COOZ, or one anhydride group must be present, and with the further proviso that when n is 1 and R.sup.1 or R.sup.3 is --COOZ, then neither R.sup.2 nor R.sup.4 is --COOZ;
• or when n is 0, R.sup.2 or R.sup.4 is not --COOZ;
• or
• (B) is a non-toxic base addition salt of a compound of formula II which contains a free carboxy group.