Use of one or more soluble fatty amines in a lubricating composition to passivate all or part of the surface of metal parts of an engine, preferably of a marine engine and prevent and/or reduce the metallic losses of said metal parts, wherein the fatty amine is chosen from among: - the compounds of formula: R 1 -[(NR 2)-R 3] m -NR 4 R 5, in which, • R 1 represents a saturated or unsaturated hydrocarbon group, linear or branched, comprising from 12 to 22 carbon atoms, • R 2, R 4 or R 5 independently represent a hydrogen atom, a saturated or unsaturated, linear or branched, alkyl group comprising between 1 and 22 carbon atoms or a (R 6 -O) q -H group wherein R 6 is a saturated, linear or branched, alkyl group comprising between 2 and 6 carbon atoms, and q represents an integer greater than or equal to 1, • R 3 represents a saturated or unsaturated, linear or branched, alkyl group comprising between 2 and 6 carbon atoms; • m is an integer between 1 and 10, more preferably between 1 and 6, still more preferably selected from among 1, 2 or 3; or - a mixture of one or more polyalkylamines of formulas and/or: in which • R, identical or different, represents a linear or branched alkyl group comprising from 8 to 22 carbon atoms, • n and z, independently of each other, represent 0, 1, 2 or 3, and • o and p represent 0, 1, 2 or 3 independently of each other when z is greater than 0, wherein said mixture comprises at least 3% by weight of branched compounds such as at least one of n or z is greater than or equal to 1, or derivatives thereof; or - a mixture of fatty amines of formulas, and/or. - the compounds of formula: R 1 -[(NR 2)-R 3] m -NR 4 R 5, in which, • R 1 represents a saturated or unsaturated hydrocarbon group, linear or branched, comprising from 12 to 22 carbon atoms, • R 2, R 4 or R 5 independently represent a hydrogen atom, a saturated or unsaturated, linear or branched, alkyl group comprising between 1 and 22 carbon atoms or a (R 6 -O) q -H group wherein R 6 is a saturated, linear or branched, alkyl group comprising between 2 and 6 carbon atoms, and q represents an integer greater than or equal to 1, • R 3 represents a saturated or unsaturated, linear or branched, alkyl group comprising between 2 and 6 carbon atoms; • m is an integer between 1 and 10, more preferably between 1 and 6, still more preferably selected from among 1, 2 or 3; or • R 1 represents a saturated or unsaturated hydrocarbon group, linear or branched, comprising from 12 to 22 carbon atoms, • R 2, R 4 or R 5 independently represent a hydrogen atom, a saturated or unsaturated, linear or branched, alkyl group comprising between 1 and 22 carbon atoms or a (R 6 -O) q -H group wherein R 6 is a saturated, linear or branched, alkyl group comprising between 2 and 6 carbon atoms, and q represents an integer greater than or equal to 1, • R 3 represents a saturated or unsaturated, linear or branched, alkyl group comprising between 2 and 6 carbon atoms; • m is an integer between 1 and 10, more preferably between 1 and 6, still more preferably selected from among 1, 2 or 3; or - a mixture of one or more polyalkylamines of formulas and/or: in which • R, identical or different, represents a linear or branched alkyl group comprising from 8 to 22 carbon atoms, • n and z, independently of each other, represent 0, 1, 2 or 3, and • o and p represent 0, 1, 2 or 3 independently of each other when z is greater than 0, wherein said mixture comprises at least 3% by weight of branched compounds such as at least one of n or z is greater than or equal to 1, or derivatives thereof; or • R, identical or different, represents a linear or branched alkyl group comprising from 8 to 22 carbon atoms, • n and z, independently of each other, represent 0, 1, 2 or 3, and • o and p represent 0, 1, 2 or 3 independently of each other when z is greater than 0, - a mixture of fatty amines of formulas, and/or.