The present invention relates to an additive composition comprising: (A) at least one (per)fluoropolyether polymer [PFPE polymer.sub.add] comprising a (per)fluoropolyether chain [PFPE chain.sub.add] having a first chain end and a second chain end bonded to opposite sides of said PFPE chain.sub.add, wherein: the first chain end comprises a group of formula C(O)NR.sub.aR.sub.b, wherein R.sub.a and R.sub.b, each independently, are selected from: hydrogen, linear or branched C.sub.1-C.sub.6 alkyl group; the second chain end comprises a group selected from: C.sub.1-C.sub.6 (per)fluoroalkyl group, CF.sub.2C(O)CF.sub.3 and C(OH).sub.2CF.sub.3; C(O)NR.sub.aR.sub.b, wherein R.sub.a and R.sub.b, each independently, are selected from: hydrogen, linear or branched C.sub.1-C.sub.6 alkyl group; C(O)OR.sub.c, wherein R.sub.c is a linear or branched C.sub.1-C.sub.6 alkyl group; (B) 0.01-25.0 wt. %, based on the weight of component (A), of a fluorescent dye of formula (I) (e.g. a rhodamine dye). The present invention also relates to the use of the additive composition in admixture with hydrogenated or fluorinated lubricants. The additive composition is capable of imparting the lubricant with both anti-rust and fluorescence properties.

The present invention relates to an additive composition comprising: (A) at least one (per)fluoropolyether polymer [PFPE polymer.sub.add] comprising a (per)fluoropolyether chain [PFPE chain.sub.add] having a first chain end and a second chain end bonded to opposite sides of said PFPE chain.sub.add, wherein: the first chain end comprises a group of formula C(O)NR.sub.aR.sub.b, wherein R.sub.a and R.sub.b, each independently, are selected from: hydrogen, linear or branched C.sub.1-C.sub.6 alkyl group; the second chain end comprises a group selected from: C.sub.1-C.sub.6 (per)fluoroalkyl group, CF.sub.2C(O)CF.sub.3 and C(OH).sub.2CF.sub.3; C(O)NR.sub.aR.sub.b, wherein R.sub.a and R.sub.b, each independently, are selected from: hydrogen, linear or branched C.sub.1-C.sub.6 alkyl group; C(O)OR.sub.c, wherein R.sub.c is a linear or branched C.sub.1-C.sub.6 alkyl group; (B) 0.01-25.0 wt. %, based on the weight of component (A), of a fluorescent dye of formula (I) (e.g. a rhodamine dye). The present invention also relates to the use of the additive composition in admixture with hydrogenated or fluorinated lubricants. The additive composition is capable of imparting the lubricant with both anti-rust and fluorescence properties.