Galvanic studies of copper coupled to alloy 33 and titanium in lithium bromide solutions

Galvanic influence of Alloy 33 (UNS R20033) and titanium (Grade 2) on copper was studied in lithium bromide (LiBr) solutions (400, 700, and 850 g/L chromate containing commercial solution). Temperature effect was also analyzed by imposing a heating/cooling cycle to the samples during a 10-h period (from 25degreesC to 80degreesC at 0.5degreesC/min), during a 2-h period (from 80degreesC to 25degreesC at 0.5degreesC/min), and during the last 2 h (maintained at 25degreesC). The galvanic potential and the galvanic current were measured with a zero-resistance ammeter (ZRA) during the temperature cycle. Images of the electrode surfaces were captured simultaneously with the recorded electrochemical signal caused by corrosion processes without disturbing the electrochemical system. The experimental device consists of an electrochemical system with an horizontal electrochemical cell coupled to a microscope, camera, and a system of image acquisition. Copper is always the anodic element of the Cu-Alloy 33 pair, however it behaves cathodically or anodically, depending on the temperature and the medium, when coupled to titanium. Copper was the cathodic element of, the Cu-Ti pair in 700 g/L LiBr solution and commercial solution at room temperature. In these cases, the cooling stage generated the highest galvanic current. Temperature effect on the corrosion of the Cu-Alloy 33 pair duplicated >52degreesC according to the current slope values observed during the second heating hour The cooling period also caused a galvanic current increase between 70degreesC and 65degreesC. Initial current and potential values were not recovered. at the end of the cycle in the commercial LiBr solution.