A composition containing a substituted cyclic anhydride and a hydroxy-oxime. The cyclic anhydride may be a succinic anhydride derivative such as dodecenyl succinic anhydride or a polymer containing cyclic anhydride groups such as polyisobutenyl succinic anhydride. The oxime may be 2-hydroxy-5-nonylbenzaldoxime or 2-hydroxy-5-nonylacetophenone oxime. The composition may be used to inhibit corrosion of metals, particularly iron. The composition may also include further components which are effective to reduce metal corrosion.