Corrosion inhibitors for fuels and lubricants

A method for inhibiting corrosion of a metal surface, the method comprising:

• applying a corrosion inhibitor to at least one of an iron surface, a steel surface and a nonferrous metal surface, wherein the corrosion inhibitor comprises a copolymer obtained by a process comprising:
• copolymerizing by addition polymerization:
• (A) at least one ethylenically unsaturated mono- or dicarboxylic acid or a derivative thereof selected from the group consisting of an anhydride in a monomeric or a polymeric form, a mono- or dialkyl ester, and a mixed ester,
• (B) at least one α-olefin comprising from 16 to 28 carbon atoms,
• (C) optionally at least one aliphatic or cycloaliphatic olefin which comprises at least 4 carbon atoms and is different than (B), and
• (D) optionally at least one copolymerizable monomer other than (A), (B) and (C), which is selected from the group consisting of (Da) a vinyl ester, (Db) a vinyl ether, (Dc) a (meth)acrylic ester of an alcohol comprising at least 5 carbon atoms, (Dd) an allyl alcohol or ether thereof, (De) a N-vinyl compound selected from the group consisting of a vinyl compound of a heterocycle comprising at least one nitrogen atom, a N-vinylamide, and a N-vinyllactam, (Df) an ethylenically unsaturated aromatic, (Dg) an α,β-ethylenically unsaturated nitrile, (Dh) a (meth)acrylamide, and (Di) an allylamine,
• thereby obtaining a first copolymer;
• and
• subsequently partly or fully hydrolyzing anhydride or carboxylic ester functionalities present in the first copolymer into acid groups so that a content of the acid groups in the copolymer is from 1 to 8 mmol acid groups per gram of the copolymer, thereby obtaining the copolymer,
• wherein the copolymer has a weight-average molecular weight Mw determined by gel permeation chromatography with tetrahydrofuran and polystyrene as standard of 1.5 to 4 kDa.