Abstract
Acridines (acridine, 9-methylacridine and 9-propylacridine) and acridans (acridan, 9-methylacridan and 9-propylacridan) have been examined as corrosion inhibitors for aluminum by three types of coupon test as follows:
1) Adding an inhibitor alone in dilute HCl solution.
2) Pre-filmed coupon test in dilute HCl solution: the filmed coupon is prepared by dipping itself in the inhibitor-containing dioxane.
3) Adding tetralin solution of an inhibitor in salted water with a dispersant. As results, the efficiencies were summarized as follows:
1) acridines>acridans, 2) acridans>acridines
3) acridans>acridines
Acridines can always protect aluminum by filming metallic surface with an active form of resonance structures, while acridans can protect the metal only when they are released from their molecular-association of hydrogen bonding.
A lone pair of electrons of N-atom in acridans. may be donated only when released from hydrogen: bond association, but in acridines may always be donated from their active form.
Acridans show better inhibition only when they are adsorbed on the metal apart from their molecular-association, while acridines always give the same characteristics of inhibition comparatively as dissociated acridans.
