Corrosion inhibitors for fuels and lubricants

A process of reducing corrosion on a surface comprising iron, steel, copper, or a copper alloy, the process comprising:

• contacting the surface with a corrosion inhibitor in the presence of sodium, potassium, magnesium, calcium, and/or zinc ions,
• wherein the corrosion inhibitor comprises a reaction product of polyisobutene comprising free acid groups, the reaction product comprising, in reacted form:
• (A) a polyisobutene having a number-average molecular weight Mn in a range of from 200 to 10000 and (B) an α,β-unsaturated monomer that is a monocarboxylic acid, dicarboxylic acid, monoalkyl ester, dialkyl ester, or anhydride, in a stoichiometric ratio of more than one equivalent of the α,β-unsaturated monomer (B) per reactive double bond in the polyisobutene (A),
• wherein the reaction product has a bismaleation level in a range of from at least 12% to 40%, and
• wherein, when the monomer (B) comprises the monoalkyl ester and/or the dialkyl ester, at least 10% of the ester groups present in the reaction product are in hydrolyzed form, and/or
• wherein, when the monomer (B) comprises the anhydride, at least 10% of the anhydride groups present in the reaction product are in hydrolyzed form.