Effect of Oxidizing Agents on Corrosion Resistance of Commercially Pure Titanium in Nitric Acid Solution

Satoh Hiroshi, Kamikubo Fumio, Shimogori Kazutoshi, Fukuzuka Toshio

doi:10.3323/jcorr1974.31.12_769

Titanium is one of the candidate materials for solidification process equipment of high level liquid waste produced in reprocessing of spent nuclear fuel from Light Water Reactors.<br>The high level liquid waste is a nitric acid solution containing various kinds of oxidizing agents such as Cr₂O₇^2-, Fe³⁺ and Ce⁴⁺ ions and is very corrosive to metallic materials. Therefore, effect of oxidizing agents on corrosion resistance of commercially pure titanium in nitric acid solution was investigated using gravimetric and electrochemical techniques.<br>As a result, it was clarified that corrosion resistance of titanium was markedly improved by adding oxidizing agents having high redox potentials. The peak height ratio of O 1s/Ti 2P obtained from ESCA spectra for the specimens revealed that the passive film formed in Cr₂O₇^2- free nitric acid solution consisted of Ti₂O₃ but it formed in the solution with Cr₂O₇^2- consisted of TiO₂ which was more stable thermodynamically. This is the reason why Cr₂O₇^2- inhibits titanium to corrode. Cr₂O₇^2- seems to oxidize dissolved Ti³⁺ in the solution to Ti⁴⁺ and TiO₂ would form by following reaction; Ti⁴⁺+2H₂O→TiO₂+4H⁺.<br>Furthermore, titanium showed an excellent corrosion resistance in the simulated high level liquid waste even at high temperature.<br>From these results, it is considered that titanium is a suitable material for the solidification process equipment.

Effect of Oxidizing Agents on Corrosion Resistance of Commercially Pure Titanium in Nitric Acid Solution

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