Investigation of titanium corrosion in concentrated NaOH solutions

Abstract

The rate of both spontaneous and polarization assisted formation of oxide films on commercially grade titanium, DIN 3.7025, was studied in concentrated, 1-5M NaOH solutions, with particular attention to the early stages of oxide formation. Simultaneous chemical dissolution of oxides was considered. The rate of spontaneous oxide formation was examined with cyclic voltammetry as an in-situ method. The shape of potentiodynamic curves recorded in different alkaline solutions indicated that the electrolyte concentration affects the oxide composition. Titanium electrodes were covered with oxide films of different thickness, and the time dependence of polarization resistance was measured under a fixed anodic polarization. The polarization resistance may either increase or decrease tending to attain a stationary value, which, for a fixed polarization, depends on both the initial thickness and the NaOH concentration. © WILEY-VCH Verlag GmbH, D-69451 Weinheim, 2002.