Inhibition by Precipitation of Compounds

Precipitates at surfaces block both reactions, metal dissolution and redox processes. In both cases, diffusion is most likely the rate-determining step. Dissolved metal ions have to diffuse through pores from the metal surface to the bulk electrolyte and similarly the redox species from the bulk to the metal surface. Benzotriazole (BTA) is an inhibitor, which forms thick layers with cations, which act as a diffusion barrier. For example, copper forms an insoluble compound with BTA. It has been shown that the dissolution of a 

Inhihitian efficiency T i and surface coverage 0 for steel in 0.5M H2SO4 with addition of n-hexylamine, n-octylamine, n-decylamlne, and n-dodecylamine as inhibitors. (From Szklarska-Smialowska, Z. and Wieczorek, 

in Proceedings of 3rd European Symposium on Corrosion Inhibitors, Ferrara, 1970, Annali deU universita di Ferrara, Sezione V, Suppl. N. 5,1971, p. 453.) 

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