Nippon Mining & Metals Co., Ltd.

Nippon Mining Co., Ltd.

Yasuhiro Mitsuyoshi

Kazuhiro Taki

Takeshi Shiraki

The invention provides (1) a titanium alloy with excellent corrosion resistance consisting essentially of 10-40 wt % of Mo, 0.1-15 wt % of Cr, and the balance of Ti and unavoidable impurities and (2) a titanium alloy according to (1) which further contains 0.01-2.0 wt % (in total) of Ru, Ir, Os, Pd, Pt, or/and Rh. The addition of Mo allows Ti-based alloys to form on the surface a protective film with a high concentration of Mo, whereby their corrosion resistance in non-oxidizing acids, such as hydrochloric and sulfuric acids, is markedly improved. In environments where oxidants are present, even but a few ppm in amount, Mo comes out in solution, seriously affecting the corrosion resistance of the alloys. To avoid this, Cr must also be added. The addition of Cr helps keep Mo from dissolving out and thereby prevent the deterioration of corrosion resistance by the action of oxidants in the environments. The platinum group elements, singly or in combination, further improve the corrosion resistance.

Titanium alloys with excellent corrosion resistance

A process for producing a titanium material with excellent corrosion resistance, which comprises first applying a degree of cold working of 10% or more of the total working reduction while causing an oil to exist on the surface of the titanium material during cold working thereof and then subjecting the titanium material to in-situ heat treatment at a temperature of 300.degree. C. or higher, thereby forming a layer with excellent corrosion resistance containing at least one of Ti.sub.2 N, TiC and Ti(CN) on the titanium material surface.

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Samukawa, Japan

Yasuhiro Mitsuyoshi