Corrosion Inhibition in Acid Solution

Cylinders of iron, zinc, and cadmium were rotated in a highly corrosive solution of acid containing nitrate ion as a depolarizer, as described previously. Three kinds of inhibitors were added to the solution : ( a ) dichromate ion plus complexing or chelating agents for metal ions; ( b ) a wetting or emulsifying agent which is strongly adsorbed; and ( c ) a reagent which forms a very insoluble precipitate with ferrous and ferric ions. Measurements of the effectiveness of these inhibitors are given.