Synthesis of High-Efficiency Melamine Quaternary Ammonium Salt and Its Corrosion Inhibition Performance in a Hydrochloric Acid Environment

A novel melamine-derived quaternary ammonium salt corrosion inhibitor (Me-B) was synthesized using melamine and benzyl bromide as raw materials. Systematic evaluation of its corrosion inhibition performance for N80 carbon steel in a 15 wt % HCl solution was conducted via weight loss measurements and electrochemical techniques. Experimental results demonstrate that Me-B exhibits outstanding performance. At 363 K, the addition of 0.1 wt % Me-B significantly reduced the corrosion rate of N80 steel from 1,258.36 g·m–2·h–1 to 19.75 g·m–2·h–1, corresponding to an inhibition efficiency of 98.4%. Even at elevated temperatures up to 383 K, Me-B retained measurable corrosion inhibition capability. Adsorption of Me-B on the N80 steel surface follows a mixed physical-chemical mechanism consistent with the Langmuir adsorption model, which elevates the energy barrier for corrosion reactions and impedes their progression. Theoretical calculations elucidated the inhibition mechanisms of both neutral Me-B and protonated Me-B (Me-BH+), revealing that Me-BH+ possesses superior reactivity and enhanced adsorption affinity toward the metal surface compared to neutral Me-B. This facilitates the formation of a compact protective film that effectively blocks corrosive medium penetration, thereby mitigating acid-induced metal corrosion.