Dissolution of brass 70/30 (Cu/Zn) and its inhibition during the acid wash in distillers

The corrosion behaviour of brass 70Cu/30Zn in deaerated solutions of pure dilute HCl and acidified 4% NaCl of pH 1.8-2 was studied at different temperatures between 25 and 60 degrees C by the weight loss method. The curves representing the variation of loss in weight with time indicate that there is an induction period followed by a linear relation. Analysis of the solution by the atomic absorption technique and investigation. of the surface by scanning electron microscopy indicate that the linear relation begins at a critical value of copper-ion concentration of the corrodent due to autocatalysis. The addition of different concentrations of CuCl2 eliminates the induction period and increases the corrosion rate. The effect of the addition of different concentrations of 2-methyl benzimidazole (MBIA) and Armohib 28 inhibitors on the dissolution of the alloy in both media was tested at 60 degrees C. MBIA has no effect in the case of acidified 4% NaCl, but with pure dilute HCl the inhibition efficiency in the presence of 300 p.p.m. MBIA amounted to 84.6%. On the other hand, the inhibition efficiency reached 93.4% and 94.6% in the presence of 10 p.p.m. Armohib 28 inhibitor in pure dilute HCl and acidified 4% NaCl, respectively.