Corrosion behavior of the Ti-4% Al-4% V alloy in boiling nitric acid solutions

Electron beam melting of Ti-6% Al-4% V scrap was carried out to investigate the possibility of recycling this alloy, which is available in large amoun ts worldwide. A possible application of the recycled alloy would be the fab rication of HNO3-resistant equipment and other devices. Aluminum losses wer e verified in all runs, which has led to the production of an alloy with a nominal composition of Ti-4% Al-4% V. Tensile tests have pointed out that T i-4% Al-4% V has mechanical properties close to the Ti-6% Al-4% V alloy. Immersion corrosion tests were accomplished in boiling nitric acid solution s and the results have shown that the Ti-4% Al-4% V alloy is less resistant than commercially pure titanium to general dissolution. When the solutions were periodically renewed every 24 h, the corrosion rates were almost cons tant. When the solutions were not changed, the corrosion rates decreased wi th time. This behavior was due to the formation of Ti4+ ions by the corrosi on process of the alloy which enhanced passivation, forming superficial TiO 2 rutile oxide. The observed passivity of the Ti-4% Al-4% V alloy could tur n it into a promising material for nitric acid storage tanks, batch reactor s and fastening fittings. (C) 1999 Elsevier Science Ltd. All rights reserve d.