Patent ID: 7377292

Claim:
A vehicular brake system component used in a brake system of a vehicle, comprising: a pressure vessel having a gas chamber in which a gas is sealed and a liquid chamber adapted to be filled with a liquid; a diaphragm, which has a fixed end fixed to the pressure vessel and a free end capable of extending and contracting in a direction of an axis of the pressure vessel, and which is located in the pressure vessel to separate the gas chamber and the liquid chamber; a partition wall located in the liquid chamber and having a circulation port through which the liquid in the liquid chamber flows in or out; and a seal member which closes the circulation port in a liquid-tight manner to confine the liquid between the partition wall and the diaphragm when the free end of the diaphragm is at a given position; wherein the seal member comprises a metal member, an adhesive layer provided on at least a part of the surface of the metal member, and an elastic rubber member bonded to the metal member with the adhesive layer therebetween; wherein the metal member comprises a metal member body and a protective film which is provided on a surface of the metal member body and restrains degradation of the metal member body; and wherein the protective film is zinc calcium phosphate film having a crystal grain size of 8 μm or less.