Corrosion Behaviour of Ti–4Al–4V Alloy in Nitric, Phosphoric and Sulfuric acid Solutions at Room Temperature

Author： Robin A. Rosa J.L. Sandim H.R.Z.

ISSN： 0021-891X

Source： Journal of Applied Electrochemistry, Vol.31, Iss.4, 2001-04, pp. : 455-460

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Abstract

Electron beam melting of Ti-6-4 scrap has been carried out. Aluminium losses were verified for all the runs and commercial-size ingots of Ti-4-4 alloy were obtained. Tensile tests and hardness measurements have shown that the Ti-4-4 alloy has mechanical strength close to the Ti-6-4 alloy as well as higher ductility. The corrosion behaviour of the Ti-4-4 alloy was investigated in HNO_3, H_3PO_4 and H_2SO_4 solutions at room temperature. Ti-4-4 alloy is passive in all HNO_3 solutions and in 20 wt% H_3PO_4 and presents an active behaviour in 40–80 wt% H_3PO_4 and in all H_2SO_4 solutions. Ti-4-4 alloy is highly corrosion resistant in HNO_3 and 20 wt% H_3PO_4 and has a moderate resistance in 40 wt% H_3PO_4. Ti-4-4 alloy can be regarded as a potential candidate to replace CP–Ti in these media. In more concentrated H_3PO_4 solutions, and in H_2SO_4, very high corrosion rates were observed.