SYNERGISTIC EFFECTS IN THE INHIBITION OF COPPER CORROSION

Benzotriazole (BTA), thiourea (TU), and potassium ethylxanthate (KEX), behave as copper (Cu) corrosion inhibitors under certain conditions. These chemicals have been investigated to establish whether they provide synergistic effects. The Cu corrosion inhibition was followed through changes in electrochemical characteristics. Cu specimens were tested at 25-degrees-C in two aggressive media, 0.1 M NaCl and 1 M NaClO4 using the linear potential sweep technique at 0.001 V s-1 and by scanning electron microscopy of Cu specimens subjected to potentiodynamic and potentiostatic routines. A comparative behavior of the different substances for Cu was presented in the 6.6 less-than-or-equal-to pH less-than-or-equal-to 11 range. For KEX-BTA mixtures, synergistic inhibition effects were found in 0.1 M NaCl (7 less-than-or-equal-to pH less-than-or-equal-to 11). The apparent synergistic inhibition was explained tentatively by an increase in the compactness of the polymer-like passivating layer of KEX-Cu, which formed in the presence of BTA and Cl- ions.