An additive for an aqueous metalworking fluid (MWF) comprises a C12-20 fatty acid neutralized with at least one of an amine, alkanolamine and a caustic. The additive is designed for use in an aqueous MWF having a pH of at least about 7 and comprising at least about 0.10 weight percent, based on the weight of the MWF, of the neutralized C12-20 fatty acid. The additive inhibits the staining of ferrous and nonferrous metals during and after machining.
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