Tailoring Ionic Liquid Corrosion Inhibitors for N80 Steel in Acidic Media: Anion–Cation Synergy, High-Temperature Performance, and Multiscale Mechanistic Insights

In petroleum extraction, acidizing agents can enhance reservoir permeability but severely corrode metal equipment. Traditional acidizing corrosion inhibitors exhibit poor thermal stability at high temperatures, being prone to decomposition or denaturation, which significantly diminishes their film-forming and corrosion-inhibiting capabilities. In contrast, ionic liquid corrosion inhibitors demonstrate exceptional thermal stability under extreme conditions, making them a highly promising alternative. Through the innovative integration of multiscale mechanistic research methodologies, this study systematically evaluated the corrosion inhibition performance of six acidizing inhibitors using weight loss tests, complemented by electrochemical analysis, quantum chemical calculations, molecular dynamics simulations, adsorption energy analysis, surface characterization, and adsorption thermodynamic studies. The electrochemical tests indicate that the corrosion inhibitor exhibits inhibitory effects on both the anodic and cathodic corrosion processes, classifying it as a mixed-type inhibitor. Quantum chemical calculations revealed the interaction mechanism between inhibitor molecules and metal atoms, characterized by electron donation from inhibitor molecules and electron acceptance by metal atoms. Thermodynamic analysis reveals that the adsorption process conforms to the Langmuir model (<i>R</i>² > 0.99). Molecular dynamics simulations demonstrate that the corrosion inhibitor forms strong interactions with the metal surface through a planar adsorption configuration, effectively hindering charge transfer and inhibiting ion diffusion. Thermogravimetric analysis confirms no significant decomposition below 250 °C, meeting the requirements of green chemistry. Experimental and computational evaluations revealed three corrosion inhibitors with excellent inhibitory performance: [AMIM]N(CN)₂, [AMIM]Br, and [AMIM]Cl. Among them, 1.5% [AMIM]N(CN)₂ achieved a corrosion inhibition efficiency of 92.07% at 60 °C. This study provides a solid theoretical foundation for metal corrosion protection under high-temperature conditions and offers critical insights and scientific guidance for developing advanced corrosion inhibitors with enhanced thermal stability and superior inhibition performance.