Patent ID: 8067344

Claim:
A method of preventing corrosion of a copper surface or a silver surface by a sulfide gas which method comprises applying a lubricating grease composition to a copper surface or a silver surface, the lubricating grease composition consisting of a fluoro resin and a base oil consisting of a mixture of 100 parts by weight of at least one of a perfluoropolyether oil (A), represented by the following general formula: RfO[CF(CF 3 )CF 2 O] p (CF 2 CF 2 O) q Rf where Rf is a perfluoroalkyl group having 1-5 carbon atoms, p+q=2-200, q/p=0-2, q may be 0, and CF(CF 3 )CF 2 O group and CF 2 CF 2 O group are bonded at random in the main chain and a perfluoropolyether oil (B), represented by the following general formula: F(CF 2 CF 2 CF 2 O) s C 2 F 5 where s=2-100, and 2-100 parts by weight of at least one of a perfluoropolyether oil (C), represented by the following general formula: RfO(CF 2 CF 2 O) m (CF 2 O) n Rf where Rf has the same meaning as defined above, m+n=3-200, m:n=10-90:90-10, and CF 2 CF 2 O group and CF 2 O group are bonded at random in the main chain, and a perfluoropolyether oil (D), represented by the following general formula: RfO[CF(CF 3 )CF 2 O] a (CF 2 CF 2 O) b (CF 2 O) c Rf where Rf has the same meaning as defined above, a+b+c=3-200, b is 0 or an integer of 1 or more, c is an integer of 1 or more, and CF(CF 3 )CF 2 O group, CF 2 CF 2 O group, and CF 2 O group are bonded at random in the main chain, and exposing the copper surface or silver surface having the lubricating grease applied thereto to a sulfide gas whereby the applied lubricating grease prevents corrosion of the copper surface or silver surface by the sulfide gas.