Optimization of a flaxseed–carrageenan–KI green inhibitor system for P22 steel in 1 M HCl using Box–Behnken design and electrochemical validation

Zavaleta-Gutierrez N.; Otiniano-Mendez D.; Carrasco-Muñoz J.; Polo-Briceño E.; Ñique-Gutierrez N. · Results in Engineering (2026) · DOI: 10.1016/j.rineng.2026.111072

Resumen

Natural polysaccharides have emerged as attractive eco-friendly corrosion inhibitors, although the optimization of multicomponent bio-based systems under harsh acidic conditions remains poorly understood. In this work, a ternary green inhibitor system composed of flaxseed mucilage (FSM), carrageenan extracted from Chondracanthus chamissoi (CCC), and potassium iodide (KI) was rationally designed for the corrosion protection of P22 steel in 1 M HCl at 65 °C. A Box–Behnken response surface methodology integrated with gravimetric analysis was applied to evaluate the individual, quadratic, and interaction effects of the three components on corrosion rate (CR) and inhibition efficiency (IE). The developed quadratic models exhibited excellent predictive capability (R² = 0.9998) with non-significant lack-of-fit, enabling reliable multi-response optimization. The optimum formulation (0.40 g L⁻¹ FSM, 0.60 g L⁻¹ CCC, and 5 mM KI) reduced the corrosion rate from 26.97 to 1.58 mm year⁻¹ and achieved an inhibition efficiency of 94.14 %. Electrochemical validation through potentiodynamic polarization, electrochemical frequency modulation, and electrochemical impedance spectroscopy confirmed strong suppression of corrosion kinetics and mixed-type inhibition behavior. EIS analysis revealed a substantial increase in charge-transfer resistance, a marked decrease in double-layer capacitance, and a displacement of the characteristic impedance response toward lower frequencies, indicating the formation of a compact and stable polysaccharide–iodide interfacial barrier. SEM/EDS analyses further demonstrated the development of a homogeneous protective film with minimal chloride incorporation on the steel surface. The results demonstrate that the integration of natural polysaccharides, iodide ions, and statistically guided optimization provides an effective strategy for developing environmentally sustainable corrosion inhibitor systems for industrial acid-cleaning applications.

Instituciones: Universidad Nacional de Trujillo