Patent ID: 6791245
Filing Date: 2004-09-14
Classification: C23C,E04F,F23Q,H01T

Abstract:
A method of manufacturing a spark plug incorporating a central electrode, an insulating member disposed on the outside of said central electrode, a main metal shell disposed on the outside of said insulating member and a ground electrode disposed opposite to said central electrode to form a spark discharge gap, said method of manufacturing a spark plug comprising the step of:immersing said main metal shell in a chromate processing bath containing trivalent chrome salt and a complexing agent for said trivalent chrome mixed therein so that a chromate film containing trivalent chrome by 95 wt % or more of contained chrome components and having a thickness of 0.2 &mgr;m to 0.5 &mgr;m is formed on the surface of said main metal shell.