Influence of Zinc and Lead on Brass Corrosion in Dilute Sulfuric Acid

The corrosion behavior of Cu-Zn alloys in sulfuric acid (H2SO4) solutions was investigated using open-circuit potential measurements, potentiodynamic techniques, and electrochemical impedance spectroscopy. The influence of alloy composition, H2SO4 concentration, and temperature on the corrosion response of the alloys was discussed. A comparison between the behaviors of the alloys and their constituent elements (Cu and Zn) under the same experimental conditions was carried out. The thickness and resistance of the surface film, formed on the alloy, increase as the Zn content is increased up to 31.1%, before they start to decrease again. The addition of Pb, as a minor alloying element, to the brass alloy (Cu-38Zn) leads to a significant decline in the corrosion rate of the alloy due to the formation of an insoluble lead sulfate (PbSO4) layer. Prolonged immersion of the alloys in H2SO4 solutions improves their corrosion resistance. The calculated activation energy of the alloy dissolution process reveals that its corrosion obeys activation kinetics. The electrochemical impedance data were analyzed using an equivalent circuit model consisting of contributions to two time constants representing the double layer and the surface film. The influence of the alloy composition and H2SO4 concentration on the equivalent circuit parameters was found to be in agreement with the results of the direct current (DC) measurements.