%0 Journal Article
%T Schiff Bases of Triethylenetetramine as Corrosion Inhibitors of Zinc in Hydrochloric Acid
%A M.D. Shah
%A A.S. Patel
%A G.V. Mudaliar
%A N.K. Shah
%J Portugaliae Electrochimica Acta
%D 2011
%I Sociedade Portuguesa de Electroqu¨ªmica
%X The performance of triethylenetetramine-tribenzylidene (TTTB) and triethylenetetramine-trisalicylidene (TTTS) as corrosion inhibitors for zinc in hydrochloric acid is investigated. At lower concentrations, both inhibitors accelerate the attack but inhibit corrosion at higher concentrations, e.g., 96-100% with 1.0% concentration in 0.5 M and 1.0 M HCl. The efficiency of TTTB decreases while that of TTTS remains almost constant (¡Ý 99.7%) up to 120 minutes and in the temperature range 35 - 65 oC. The activation energies are higher in inhibited than in plain acid with both inhibitors. The free energy of adsorption (¦¤Gads) and heat of adsorption (Qads) are negative, which suggests that there is spontaneous adsorption on metal surface, and from the values of (¦¤Gads) and (Qads), the values of entropy of adsorption (¦¤Sads) were calculated. Galvanostatic polarization shows that corrosion is under mixed control with predominance of the cathodic part. In uninhibited 1.0 M HCl, complete cathodic protection is achieved at a current density of 4.2224 Adm-2, but in presence of these inhibitors, much lower current densities are required. Plot of log (¦È/1-¦È) versus log Cinh gives a straight line, suggesting that inhibitors cover both the anodic and cathodic regions through general adsorption following Langmuir isotherm. The mechanism of inhibition has been proposed.
%K corrosion
%K zinc
%K hydrochloric acid
%K inhibitor
%U http://www.scielo.oces.mctes.pt/scielo.php?script=sci_arttext&pid=S0872-19042011000200004