| 摘要 |
PROBLEM TO BE SOLVED: To obtain a power steering fluid composition which can prevent the deterioration of a rubber hose exposed to high temperature and high pressure and the seizure of a small-size hydraulic pump that rotates at high speed and which is excellent in lubricity to aluminum alloys and in anticorrosiveness to copper alloys by blending a lube base oil with a zinc-base antioxidant, a monobasic linear fatty acid, a thiadiazole derivative and a benzotriazole derivative each in a specified amount. SOLUTION: The composition is obtained by blending a lube base oil comprising as mineral oil or synthetic oil with a zinc-base antioxidant (A), a monobasic linear fatty acid (B), and at least one compound (C) selected from thiadiazole derivatives represented by formula I (R<1> and R<2> are each a 1-12C linear or branched alkyl) and benzotriazole derivatives represented by formula II [R<3> is H or methyl; and X is H or -CH2 NR<4> (R<5> ) (R<4> and R<5> are each an 8-18C linear or branched alkyl)], the amounts of components A, B and C respectively being 0.1-3wt.%, 0.01-1wt.% and 0.01-0.5wt.% based on the total composition. |
