ABSTRACT:The adsorption on copper of 2-Mercaptobenzothiazole (2-MBT), a heterocyclic compound member of the tiazole family, has been investigated at different concentrations (1×10 −1 to 1×10 −6 M) in water, employing the Electrochemical Quartz Crystal Microbalance (EQCM). The frequency response over time was obtained for each concentration, showing a defined exponential behavior at higher concentrations (1×10 RESUMEN: Medición directa de la cinética de adsorción del 2-Mercaptobenzotiazol en una superficie micro cristalina de cobre.En el presente trabajo se ha investigado la adsorción del 2-Mercaptobenzotiazol (2-MBT) en cobre, un compuesto heterocíclico miembro de la familia de los tiazoles, en solución acuosa a diferentes concentraciones (1×10 −1 a 1×10 −6 M), empleando la Balanza Electroquímica de Cristal de Cuarzo (BECC). Se midió y analizó el cambio de frecuencia con respecto al tiempo para cada concentración, mostrando un comportamiento exponencial definido en el rango de concentraciones altas (1×10 −1 , 1×10 −2 y 1×10 −3 M), los cambios de frecuencia registrados se ajustaron usando la isoterma de adsorción de Langmuir obteniendo buenos coeficientes de correlación (R 2 =0,91 a 0,98). Se calculó también la fracción de superficie recubierta y se halló que se encuentra en el orden de 0,50 a 0,01 para las concentraciones altas de 2-MBT. La energía libre de adsorción calculada fue de ΔG ads =−5,59 kJ mol −1 , lo cual corresponde a un proceso de fisisorción.

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Adsorption kinetics of benzothiazole (BNS) and mercaptobenzothiazole (2-MBT) (1×10-1M, 1×10-2M and 1×10-3M) were studied during 5000 s on gold and silver coated At-cut quartz microelectrodes, using EQCM. The frequency change fits well to the Langmuir isotherm in the case of 2-MBT, while BNS presents adsorption-desorption periods making the fitting non realiable. The calculated ΔGads of 2-MBT corresponds to physisorption Ag (-1.38 kcal mol-1) and Au (-1.94 kcal mol-1). On both metal surfaces (Au and Ag) the amount of adsorbed mass for 2-MBT is significantly larger (20.76 μg cm-2 and 6.03 μg cm-2) than on BNS (0.33 μg cm-2 and 0.88 μg cm-2). These facts could be explained by the deprotonation of 2-MBT giving place to an anion, which is prone to interact with both positively charged surfaces of Au and Ag. However, BNS protonates giving place to a cation and making more difficult its adsorption on both metals.

This study reports a multiscale electrochemical investigation of the interaction between the organic compound 3-amino-1,2,4-triazole (ATA), regarded as corrosion inhibitor, and two noble metals (Cu and Au), either separated or under galvanical coupling. Open circuit potential measurements show that Cu is not protected by the application of ATA, having its potential shifted towards more negative values, while on Au exhibits a slight inhibitive effect. The adsorption free energies were determined using the electrochemical quartz crystal microbalance (EQCM), with values that correspond to physisorption on either metal. The surface reactivity of the inhibitor-modified metals in chloride-containing aqueous solution was studied using the scanning vibrating electrode technique (SVET), showing high spontaneous activity, associated to electron transfer reactions in systems containing Cu and 3-amino-1,2,4-triazole. K E Y W O R D Scopper, electrochemical quartz crystal microbalance, gold, metal-inhibitor electrochemistry, scanning vibrating electrode technique

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