To provide a trivalent chromium plating film, in which the generation of cracks penetrating from the film surface to a substrate interface is suppressed, and a sliding member coated with the trivalent chromium plating film, plating is conducted with a chromium plating bath containing trivalent chromium as a chromium source, with a second phase dispersed in a planar and/or fibrous form, such that the second phase in a planar and/or fibrous form is dispersed in the hard chromium plating film to prevent or deflect the propagation of cracks, and to suppress the increase of the crack width, thereby suppressing the propagation of cracks in the hard chromium plating film.

A phenol derivative of the present invention has a structure as represented by the formula (I):

##STR00001##

The functional groups are defined in the description. The phenol derivative can be used as the antioxidant in lubricating oil, lubricating grease, plastic, rubber, or can be used as the base oil of the lubricating oil and the lubricating grease and the antiwear additive of the lubricating oil and the lubricating grease.

A phenol derivative of the present invention has a structure as represented by the formula (I):

##STR00001##

The functional groups are defined in the description. The phenol derivative can be used as the antioxidant in lubricating oil, lubricating grease, plastic, rubber, or can be used as the base oil of the lubricating oil and the lubricating grease and the antiwear additive of the lubricating oil and the lubricating grease.

Lubricant compositions comprising (a) an oil of lubricating viscosity and (b) a phosphonate ester other than a zinc salt. The phosphonate ester may be the reaction product of (i) phosphonic acid or a monomeric ester thereof with (ii) a propanediol having hydroxy groups in both the 1 and 3 positions and one or more of the carbon atoms of the propyl units are substituted with one or more alkyl groups such that the total number of carbon atoms in the propanediol ranges from 4 to 12. The molar ratio of (i) to (ii) may be 0.9:1.1 to 1.1 to 0.9.

Lubricant compositions comprising (a) an oil of lubricating viscosity and (b) a phosphonate ester other than a zinc salt. The phosphonate ester may be the reaction product of (i) phosphonic acid or a monomeric ester thereof with (ii) a propanediol having hydroxy groups in both the 1 and 3 positions and one or more of the carbon atoms of the propyl units are substituted with one or more alkyl groups such that the total number of carbon atoms in the propanediol ranges from 4 to 12. The molar ratio of (i) to (ii) may be 0.9:1.1 to 1.1 to 0.9.

A lubricating oil composition may include a base oil (A), a zinc dithiophosphate (B) comprising a compound (B1) of formula (b-1), calcium sulfonate (C), and a seal sweller (D). In formula (b-1), R.sup.1 to R.sup.4 are each independently an alkyl group. However, at least one of R.sup.1 to R.sup.4 is a prescribed straight-chain alkyl group, and at least one of R.sup.1 to R.sup.4 is a prescribed branched chain alkyl group.

A lubricating oil composition may include a base oil (A), a zinc dithiophosphate (B) comprising a compound (B1) of formula (b-1), calcium sulfonate (C), and a seal sweller (D). In formula (b-1), R.sup.1 to R.sup.4 are each independently an alkyl group. However, at least one of R.sup.1 to R.sup.4 is a prescribed straight-chain alkyl group, and at least one of R.sup.1 to R.sup.4 is a prescribed branched chain alkyl group.

A phenol derivative of the present invention has a structure as represented by the formula (I): ##STR00001##
The functional groups are defined in the description. The phenol derivative can be used as the antioxidant in lubricating oil, lubricating grease, plastic, rubber, or can be used as the base oil of the lubricating oil and the lubricating grease and the antiwear additive of the lubricating oil and the lubricating grease.

A phenol derivative of the present invention has a structure as represented by the formula (I): ##STR00001##
The functional groups are defined in the description. The phenol derivative can be used as the antioxidant in lubricating oil, lubricating grease, plastic, rubber, or can be used as the base oil of the lubricating oil and the lubricating grease and the antiwear additive of the lubricating oil and the lubricating grease.

An additive for a lubricating composition includes an ionic tetrahedral borate compound which includes a cation and a tetrahedral borate anion having a boron atom, the boron atom has at least one aliphatic bidentate di-oxo ligand. The cation may be selected to provide detergent and/or dispersant and/or antioxidant properties to a lubricating composition.