Spark plug

• Main Authors: SUZUKI HIROFUMI, AMAKUSA SEIJI
• Format: Patent
• Language: Chinese; English
• Published: 28.04.2010
• Subjects: BASIC ELECTRIC ELEMENTS; CHEMICAL SURFACE TREATMENT; CHEMISTRY; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATIONOR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY IONIMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; COATING MATERIAL WITH METALLIC MATERIAL; COATING METALLIC MATERIAL; CORONA DEVICES; DIFFUSION TREATMENT OF METALLIC MATERIAL; ELECTRICITY; GENERATING IONS TO BE INTRODUCED INTO NON-ENCLOSED GASES; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION INGENERAL; METALLURGY; OVERVOLTAGE ARRESTERS USING SPARK GAPS; SPARK GAPS; SPARKING PLUGS; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THESURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION

A spark plug includes a metallic housing (10), an insulator (20) fixed in the metallic housing (10), a center electrode (30) fixed in the insulator (20), a ground electrode (40) opposed to the centerelectrode (30) via a spark discharge gap (50), and a protective coat formed on the surfaces of a metallic housing (10) and a gasket (12). The protective coat (15) includes a galvanized film (15a) formed on the surfaces of the metallic housing (10) and the gasket (12)and a chromate film (15b) successively laminated on the galvanized film (15a). The chromate film is hexavalent chromium-free and contains trivalent chromium as a major component. The chromate film (15b) has a film thickness not smaller than 0.05 mum and not greater than 0.18 mum, and the chromate film (15b) contains a metallic component which is robust against oxidation compared with zinc. Furthermore, the chromate film (15b) has a film hardness equal to or less than 1 GPa in the temperature range from a room temperature to 180DEG C.