Abstract: An additive composition for a metalworking fluid which comprises a reaction product obtainable by the reaction between a molar excess of an anhydride and an amine, wherein the amine is at least one amino alkyl mono- or di- alkanolamine, in particular having a structural formula (I): HOOC—R—CO—NH—X—N(R′)—Y—O—CO—R′′—COOH, wherein: X represents an alkyl group having 1 to 12 carbon atoms, preferably, 2 to 8 carbon atoms and more preferably 3 to 6 carbon atoms; Y represents a hydrocarbyl group having 2 to 12 carbon atoms, preferably 2 to 6 carbon atoms; R′ represents an alkyl or alkanol groups having 2 to 12 carbon atoms; and R and R″ independently represent hydrocarbyl groups which have up to 48 carbon atoms, preferably 2 to 28; more preferably 6 to 13 carbon atoms.