Abstract: To provide a water-based lubricant for plastic working excellent in moisture absorption resistance and corrosion resistance, with which degradation in lubricating performances such as lubricity, workability and seizure resistance may not occur even under high-temperature/high humidity environments. A water-based lubricant for plastic working, comprising a resin component containing a copolymer or homopolymer of monomers having an ethylenically unsaturated bond, including at least maleic anhydride (A), an inorganic component (B), and a solid lubricating component (C), wherein maleic anhydride moieties of the resin component (A) are blocked with a nitrogen-containing compound at a blocking ratio of 10 to 80%, and unblocked maleic anhydride moieties are neutralized with an alkaline component at a degree of neutralization of 40 to 100%.

Abstract: To provide a water-based lubricant for plastic working excellent in moisture absorption resistance and corrosion resistance, with which degradation in lubricating performances such as lubricity, workability and seizure resistance may not occur even under high-temperature/high humidity environments. A water-based lubricant for plastic working, comprising a resin component containing a copolymer or homopolymer of monomers having an ethylenically unsaturated bond, including at least maleic anhydride (A), an inorganic component (B), and a solid lubricating component (C), wherein maleic anhydride moieties of the resin component (A) are blocked with a nitrogen-containing compound at a blocking ratio of 10 to 80%, and unblocked maleic anhydride moieties are neutralized with an alkaline component at a degree of neutralization of 40 to 100%.

Abstract: In a cast-iron disc brake rotor (1), each of an outer sliding surface (2a) and an inner sliding surface (3a) is covered with a phosphate coating (8) by electrolysis of a phosphate coating solution containing therein phosphate ions, zinc ions and nitrate ions. This makes it possible to attain dramatically improved rust preventive performance for the sliding surfaces (2a) and (3a). The phosphate coating (8) has a thickness of 1 to 10 &mgr;m, a mass of 4 to 35 g/m2 and a grain size of less than 50 &mgr;m. Preferably, the thickness of the phosphate coating (8) is adjusted to 2 to 8 &mgr;m.

Abstract: In a cast-iron disc brake rotor (1), each of an outer sliding surface (2a) and an inner sliding surface (3a) is covered with a phosphate coating (8) by electrolysis of a phosphate coating solution containing therein phosphate ions, zinc ions and nitrate ions. This makes it possible to attain dramatically improved rust preventive performance for the sliding surfaces (2a) and (3a). The phosphate coating (8) has a thickness of 1 to 10 &mgr;m, a mass of 4 to 35 g/m2 and a grain size of less than 50 &mgr;m. Preferably, the thickness of the phosphate coating (8) is adjusted to 2 to 8 &mgr;m.