| Abstract: | Inhibitors of corrosion 31 (1). Contribution to the inhibition of the corrosion of zinc and brass The following compounds approved as inhibitors of the corrosion of copper are investigated as inhibitors of the corrosion of zinc and brass: 2-aminopyrimidine (A), 5-aminotetrazole monohydrate (B), benzotriazole (C), Kupferron (D), 2-mercaptopyrimidine (E), 2-mercaptothiazoline (F), 2-methyl-4-amino-5-cyanopyrimidine (G), tetrazine-B (H) and 2-amino-3,4,1-dithiazoline-1,5, thione (I). In the presence of the compounds A, B, C, E and G zinc plates are totally corroded in 15 days using standard conditions. With the compounds D, F and H the protective values are 29%, 14% and 39%. A more differentiated information is obtained with acid consumption-time-curves at constant pH using zinc powder. Only the compound C slows down the corrosion. The other compounds enhance the corrosion. In corrosion studies with mixtures of copper and zinc powders the compounds B–I inhibit the corrosion of copper. The acceleration of the corrosion in the presence of compound A was investigated. The corrosion of brass (plate, grain, powder) proceeds with primary removal of zinc. The compounds A, E, F and H are good inhibitors. The inhibition values for brass 64/36 are better than for brass 90/10. The composition of the protecting layers produced on the surface of brass in the presence of the organic inhibitors is determined by X-ray fluorescence measurements. With the inhibitors A, B, E, F and G the content of copper is over 90%, but 80% in the presence of the inhibitors C and H, which delay also the corrosion of zinc. The conception of primary loss of zinc and the subsequent production of a copper-rich copper-inhibitor-protection-layer is confirmed by determining the composition of the precipitations and of the solutions produced during the corrosion of brass. |
