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 provi de synergistic effects. The Cu corrosion inhibition was followed throu gh changes in electrochemical characteristics. Cu specimens were teste d at 25-degrees-C in two aggressive media, 0.1 M NaCl and 1 M NaClO4 u sing the linear potential sweep technique at 0.001 V s-1 and by scanni ng electron microscopy of Cu specimens subjected to potentiodynamic an d potentiostatic routines. A comparative behavior of the different sub stances 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 inhibitio n effects were found in 0.1 M NaCl (7 less-than-or-equal-to pH less-th an-or-equal-to 11). The apparent synergistic inhibition was explained tentatively by an increase in the compactness of the polymer-like pass ivating layer of KEX-Cu, which formed in the presence of BTA and Cl- i ons.