Synthesis of N-alkyl-4-(4-hydroxybut-2-ynyl) pyridinium bromides and their corrosion inhibition activities on X70 steel in 5 M HCl

N-alkyl-4-(4-hydroxybut-2-ynyl) pyridinium bromides (designated as P-n) have been synthesized and characterized. The corrosion inhibition efficiency of P-n on X70 steel in 5 M HCl was evaluated via weight loss and electrochemical methods. The results indicated that the combination of good inhibition moieties, such as alkylpyridinium and acetylenic alcohol, promoted P-n to be efficient inhibitors. Although the inhibitory efficiency of P-n decreased with elevating temperature, less reduction of the efficiency was found for the P-n with longer chain. P-n molecules were adsorbed on X70 surface by replacing water, which blocked the active sites and elevated the energy barrier for corrosion.

► Intramolecular synergism of alkylpyridinium and propargyl makes P-n an efficient inhibitor.
► Less reduction of the efficiency is found for the P-n with longer chain.
► Substitution of P-n for adsorbed water on X70 is responsible for the entropy increasing.