Influence of pH on the electrochemical behaviour of a duplex stainless steel in highly concentrated LiBr solutions

The objective is to study the influence of pH on the corrosion and passive behaviour of duplex stainless steels (DSS) using potentiodynamic measurements, potentiostatic tests and electrochemical impedance spectroscopy (EIS).DSS are spontaneously passive in heavy brine LiBr solutions. Under potentiostatic conditions at applied anodic potentials within the passive domain an equivalent circuit with two time constants is the most suitable model to describe the corrosion mechanism in the interface electrolyte/passive film/metal. pH modifies the electrochemical properties of the passivity of the alloy in a 992 g/L LiBr solution reducing its resistance with the applied potential.

Research highlights
► DSS is spontaneously passive in heavy brine LiBr solutions, except at pH 2.
► pH modifies the passive properties of the alloy in LiBr solutions.
► The passive film resistance is higher in LiBr solutions with pH range 6–8.
► pH 12 shows better resistance to general and pitting corrosion and worse repassivation ability.
► An EC with two time constants describes the interface electrolyte/passive film/metal.