Tanaka Kikinzoku Kogyo K.k.

Kenichi Kurihara

Koichi Sakairi

Kunihiro Tanaka

An object of the present invention is to provide a material for a precious metal tip of a spark plug, which has more excellent durability, particularly oxidation wear resistance than a conventional one. The precious metal alloy for the spark plug according to the present invention contains 0.2 to 6.0 wt. % Cr as an essential component, further at least any one of Fe or Ni, and the balance being Ir. Here, the amount of Fe and Ni to be added is preferably 2.0 to 12.0 wt. % in total. According to the present invention, the surface may be oxidized to form an oxide layer made from a Cr&#x2014;Fe oxide, a Cr&#x2014;Ni oxide or a Cr&#x2014;Fe&#x2014;Ni oxide. The oxide layer is formed by a diffusion treatment by heating the precious metal alloy at 300 to 900&#xb0; C. in an oxidative atmosphere, and preferably has a thickness of 5 to 100 &#x3bc;m.

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Hiratsuka, Japan

Kenichi Kurihara