Pyrimidine and thiadiazole derivatives as inhibitors of copper corrosion in sodium chloride solution

Pyrimidine and thiadiazole derivatives have been evaluated as prefilming agents and corrosion inhibitors of OFHC copper, Al-brass, 90Cu-10Ni and 70Cu-30Ni, in sodium chloride solutions. Two series of compounds have been tested: - 2-mercaptopyrimidine, 2,4-dimercaptopyrimidine, 2-mercapto,4hydroxypyrimidine, 2-mercapto,4aminopyrimidine; - 2-amino,1,3,4-thiadiazole, 2-amino,5mercapto,1,3,4-thiadiazole, 2,5-dimercapto,1,3,4-thiadiazole, 2-amino,5/ethylthio)1,3,4-thiadiazole. The elctrodes have been prefilmed by immersion in aqueous solutions of the various compounds (conc. 2x10-4M; T=80°C; t=60 min). In some cases the influence of the variation of the prefilming parameters have been evaluated. The inhibiting effect of the various additives has been studied using 1x10-3M solutions. The protective effects due to the prefilming treatments or to the presence of the additives in chloride solutions have been evaluated by recording the anodic and cathodic polarization curves and the polarization resistance values during 300-hour immersion tests in non deareated 0.1M NaCl solutions at 40°C. The nalysis of the obtained results allowed to differentiate the protectivity of the various compounds.