Inhibition of the Cu65/Zn35 brass corrosion by natural extract of Camellia sinensis

Abstract

• Camellia sinensis plant extract is non-toxic and can be use for brass corrosion inhibition. • An inhibitive effect is observed in both acid and neutral media. • The extract decreases the cathodic reaction rate more strongly than the anodic reaction rate. • The inhibition efficiency increase with immersion time. • The inhibitors easily adsorb on the brass surface by forming an inhibitive layer which prevent the surface from corrosion. In this work, the corrosion inhibition of brass was studied using natural plant extract, Camellia sinensis , in 0.1 M Na2SO4 solutions with pH 7 and pH 4. Electrochemical techniques (potentiodynamic polarization, electrochemical impedance spectroscopy) and scanning electron microscopy (SEM) were applied to study the brass corrosion behavior in presence and absence of the extract. The results indicated that the extract is a very effective corrosion inhibitor for brass corrosion process in both the acidic and neutral media by virtue of adsorption. The inhibition effect increases by time as demonstrated by the EIS monitoring for 120 h. In the blank solution the corrosion process leads to the formation of a dark oxide patina at pH 7 and induces localized corrosion morphology at pH 4. The extract presence can avoid both the dark patina and the pits formation.