Influence of the lithium molibdate inhibitor on the corrosion resistance of a duplex stainless steel in LiBr absorption machines

Autores UPV
Año
CONGRESO Influence of the lithium molibdate inhibitor on the corrosion resistance of a duplex stainless steel in LiBr absorption machines

Abstract

Lithium Bromide (LiBr) is one of the most widely used absorbents in refrigeration technology. However, the operating conditions can generate corrosion problems in the structural materials. The addition of inhibitors in the medium can reduce these corrosion problems. Duplex stainless steel could be employed in LiBr absorption machines due to their good mechanical properties and corrosion resistance. The aim of this work is the study of the influence of the lithium molibdate (Li2MoO4) inhibitor on the corrosion resistance of a duplex stainless steel in concentrated lithium bromide solutions. Cyclic potentiodynamic curves and electrochemical impedance spectroscopy measurements at open circuit potential (OCP) of samples of Alloy 900 were carried out in LiBr solutions with two concentrations (400 g/L and 992 g/L) in the absence and in the presence of different concentrations of Li2MoO4 inhibitor (5, 10, 15, and 20 ppm) at 25 ºC. Additionally, images of the electrode surface were obtained after the tests using the laser scanning confocal microscope. According to the cyclic potentiodynamic curves, the corrosion current density of Alloy 900 decreases with the concentration of Li2MoO4 inhibitor. The corrosion potential and pitting potential of Alloy 900 move to more positive values with the increase in the concentration of Li2MoO4 inhibitor. On the other hand, the polarisation resistance of Alloy 900 increases with the concentration of lithium molibdate inhibitor; these results are in agreement with those observed in the cyclic potentiodynamic curves. Furthermore, the corrosion resistance of Alloy 900 increases with the concentration of Li2MoO4 inhibitor.