Amines as Corrosion Inhibitor for B26S Aluminium in Phosphoric Acid

The inhibition of corrosion of Al‐Cu (4%) alloy B26S in decinormal solutions of phosphoric acid by different amines has been studied. The efficiency of the inhibitors increases in the order: triethylamine, di‐cyclohexylamine, diethylamine, cyclohexylamine, di‐n‐propylamine, isopropylamine, ethylenediamine, trimethylamine, n‐butylamine, dimethylamine, ethylamine, hexamine, n‐propylamine, methylamine. At constant acid concentration, the inhibitor efficiency increases with increase in the concentration of the inhibitor whereas at constant inhibitor concentration the efficiency decreases with increase in the concentration of the acid. Very little correlation appears to exist between either the pKb values or the molecular weight and the extent of inhibition. Maximum inhibition is achieved in those cases where the pH of the inhibited solution lies in the non‐corrosive range (4.5–8.5).