Rotating split ring disc electrode study of corrosion of iron in near neutral and alkaline solutions

Abstract

A rotating split ring disc electrode (RSRDE) with a sensitive triple potentiostat was constructed and used for determination of soluble ferrous and ferric species during potentiodynamic polarisation of iron in borate buffer solution (pH 8·4) and in 1 M NaOH at 25°C. The high sensitivity of the RSRDE apparatus enabled determination of these species in both solutions. In the borate solution shielding and blocking effects were observed. The shielding effect on the half ring detecting Fe³⁺ occurred at high cathodic potentials of the disc and was ascribed mainly to atkalisation of the ring due to hydroxyl ions produced on the disc. The blocking effect on the half ring detecting Fe²⁺ was caused by the deposition of solid ferric products; methods are proposed to diminish the inaccuracy associated with this effect.