Corrosion Behavior and Galvanic Coupling of Stainless Steels, Titanium, and Alloy 33 in Lithium Bromide Solutions

Abstract

The corrosion resistance and galvanic behavior of three stainless steels (SS), Alloy 33, and titanium were analyzed in commercial lithium bromide (LiBr) heavy brine solutions used in heating and refrigerating systems, with and without additives, using potentiodynamic anodic polarization measurements. Corrosion rates were determined from the Tafel slopes and inhibitor effects were also analyzed. The highest corrosion currents were obtained in the less-concentrated LiBr solution and the most negative corrosion potentials were obtained in a chromate-inhibited LiBr brine. The most effective action of the inhibitor was observed on titanium while it was least effective for Alloy 33. Critical potentials were calculated at 100 μA/cm2, and it was observed that the chromate inhibitor did not improve the resistance of SS to pitting corrosion. Galvanic current and mixed potentials were calculated for all possible combinations of the tested materials from polarization curves according to the mixed potential theory. Alloy 33 was always the anodic element of the pairs analyzed so that its corrosion resistance in the three media decreased due to the galvanic effect produced by coupling with a different material. AISI 316 (UNS S31600) was the cathodic element in the commercial solution with respect to the rest of the alloys studied.