| Abstract: | Corrosion rates of aluminium alloys 2S, 3S, M57S and B26S in aqueous solutions of aliphatic amines and the inhibition efficiency of some dyes on the corrosion of 3S aluminium in these amines has been studied. The corrosion rate increases with the amine concentration up to 0.1 M and then decreases. The general order of corrosivity of amines is: tertiary < primary < secondary while for ethanolamines, the order is: tri- < di- < monoethanolamine. The order of corrosion susceptibility of different alloys in uninhibited amines M 57S < 2S < B26S < 3S. A rise in temperature increases the corrosion rate of 3S aluminium in 0.1 M amine with the energy of activation having an almost constant value of 48.9 kJ/mol in the temperature range 20–50° C. In 0.1 M methylamine, the inhibiting efficiency of different compounds (concentration 0.1%) increases in the order: alizarin red-S (5.8%) < fluorescein sodium < eosin < congo red < phenol red < thymol blue < safranine-T < methylene blue < rhodamine-B (94.2%). The efficiency of rhodamine-B for 3S aluminium in 0.1 M solutions of various amines in creases in the order: monoethanolamine (75.4%) < cyclohexylamine < n-butylamine < triethylamine < n-propylamine < diethylamine < trimethylamine < diethanolamine < ethylenediamine < triethanolamine < dimethylamine < ethylamine < methylamine (94.2%). The increase in corrosion potential of 3S aluminium in 0.1 M amine containing 0.1% rhodamine-B and the galvanostatic polarization data indicate that the inhibitor has preponderant action on local anodes. |
