Use of polyester polyamine and polyester polyquaternary ammonium compounds as corrosion inhibitors

A method for inhibiting corrosion of a metal surface, the method comprising contacting the metal surface with a corrosion-inhibiting product obtainable by the reaction of a fatty acid, or mixture of acids, having the formula R1COOH (I), wherein R1CO is an acyl group having 8 to 24 carbon atoms, that may be saturated or unsaturated, linear or branched;

• and
• a dicarboxylic acid or a derivative thereof having the formula (IIa) or (IIb)
• wherein D is —OH, —Cl, or —OR3, wherein R3 is a C1-C4 alkyl group;
• R2 is selected from the group consisting of a direct bond, an alkylene radical of the formula —(CH2)z—, wherein z is an integer from 1 to 10, a substituted alkylene radical wherein said alkylene radical is substituted by 1 or 2 —OH groups, the group —CH═CH—, a cycloalkylene, a cycloalkenylene, and an arylene group;
• with an alkanolamine having the formula (III)
• wherein each x independently is a number between 1 and 5, and Σx on molar average is a number between 2 and 10, AO is an alkyleneoxy group having 2-4 carbon atoms, R4 is a C1-C3 alkyl group or a group [AO]x wherein AO and x have the same meaning as above, or a partial or wholly quaternised derivative thereof;
• optionally said reaction between the fatty acid, the dicarboxylic acid, and the alkanolamine is followed by a further reaction step wherein part or all of the nitrogen atoms are quaternised by reaction with an alkylating agent R5X, wherein R5 is a hydrocarbyl group, and X− is an anion derived from the alkylating agent R5X.