PYRIMIDINE AND THIADIAZOLE DERIVATIVES AS INHIBITORS OF COPPER CORROSION IN SODIUM-CHLORIDE SOLUTION

Pyrimidine and thiadiazole derivatives have been evaluated as prefilmi ng 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,4-hydroxypyrimidine, 2-mercapto,4-aminopyrimidine; - -thiadia zole,2-amino,5-mercapto,1,3,4-thiadiazole, 2,5-dimercapto,1,3,4-thiadi azole, 2-amino,5(ethylthio)1,3,4-thiadiazole. The electrodes have been prefilmed by immersion in aqueous solutions of the various compounds (conc. 2x10(-4) M; T=80 degrees C; t=60 min). In some cases the influe nce of the variation of the prefilming parameters has been evaluated. The inhibiting effect of the various additives has been studied using 1x10(-3) M solutions. The protective effects due to the prefilming tre atments or to the presence of the additives in chloride solutions have been evaluated by recording the anodic and cathodic polarization curv es and the polarization resistance values during 300-hour immersion te sts in non deaerated 0.1 NaCl solutions at 40 degrees C. The analysis of the obtained results allowed to differentiate the protectivity of t he various compounds.