Process for inhibiting corrosion of ferrous metals

A process for reducing or preventing the corrosion of ferrous alloys in contact with corrosive liquids or gases at temperatures of at least 350.degree. F. which process comprises contacting the surface of said ferrous metal alloy with a corrosive inhibiting amount of a corrosion inhibitor composition comprising the reaction product of

• (I) the reaction product of
• (A) at least one aliphatic .alpha.,.beta.-monoethylenically unsaturated aldehyde having from about 3 to about 6 carbon atoms:
• and
• (B) at least one organic polyamine represented by the formula ##STR7## wherein R is a divalent saturated C.sub.2 to C.sub.4 aliphatic hydrocarbon group:
• each R.sup.1 and R.sup.2 is independently hydrogen or a saturated alkyl amino or alkyloxy group containing from 2 to about 4 carbon atoms or when two adjacent R.sup.2 groups are taken together, they form a bridging alkylene radical containing 2 carbon atoms such that the R group containing 2 carbon atoms and two adjacent R.sup.2 groups and two nitrogen atoms form a heterocyclic ring containing 4 carbon atoms and 2 nitrogen atoms:
• x has a value from 1 to about 8:
• and components (A) and (B) are employed in a mole ratio of (A) to (B) of from about 1:1 to about 1:6:
• and
• (II)
• (A) at least one saturated or unsaturated, cyclic or acyclic aliphatic mono- or polycarboxylic acid having from about 2 to about 50 carbon atoms;
• or
• (B) at least one saturated or unsaturated, cyclic or acyclic aliphatic alkyl monohalide or alkyl polyhalide having from about 2 to about 50 carbon atoms:
• or
• (C) a combination of (II-A) and (II-B);
• wherein components (I) and (II) are employed in quantities which provide from about 0.4 to about 1 equivalent of carboxyl or halide groups from component (II) for each theoretically active amino hydrogen atom contained in component (I).