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.
