A RRDE study of the electrochemical behavior of iron in solutions containing silicate and sulphate at pH 10-13

Electrochemical studies were carried out with an iron disk/platinum ring electrode using cyclic voltammetry technique in solutions of x mol/l NaOH +y ppm SiO2 +z mol/l Na2SO4 (x=hydroxyl concentration necessary to promote pHs=10; 10.5, 11; 11.5; 12; 12.5 and 13, respectively; y=0 or 500; z=0 or 0.05). The results show that there is no detectable dissolution in a pH range of 11-13, even if sulphate is present in the solution, although this specie promotes passive him thickening. Fe(II) and Fe(III) soluble species were detected at pH=10.5 only in the absence of silicate and at pH = IO, even if silicate is present in the solution. (C) 1999 Elsevier Science Ltd. All rights reserved.