Influence of the alkyl chain on the protective effects of 1;2,3-benzotriazole towards copper corrosion. Part II: formation and characterization of the protective films

EIS measurements show that thicker, less defective, more protective and persistent surface films of BTAH alkyl-derivatives can be built up on OFHC copper by increasing the side chain length (up to six CH2 units) or the additive amount in the solution. At the same time, the process of film formation becomes more rapid. In the sulphate solution, the films are less defective and more resistent than in the chloride one, in which only the higher homologues are efficient. In the case of 10(-3)-10(-2) M BTAH containing solutions, the film thicknesses calculated by EIS spectra are not too far from those derived by QCM measurements. Moreover, these results support an almost flat orientation of the BTAH molecule on the copper surface. Although it is difficult to perform such a comparison in the case of C4-BTAH or C6-BTAH, nevertheless a likely agreement between EIS and QCM data of the film thicknesses may be determined, if low dielectric constant (epsilon(r)) values are taken into account. (C) 1999 Elsevier Science Ltd. All rights reserved.