Synergistic corrosion inhibition of low carbon steel in HCl and H2SO4 media by 5-methyl-3-phenylisoxazole-4-carboxylic acid and iodide ions

The inhibition performance of 5-methyl-3-phenylisoxazole-4-carboxylic acid (MPC) alone and in combination with potassium iodide (KI) for low carbon steel in 1.0 M HCl and H2SO4 solutions is studied using weight loss, potentiodynamic polarization (PDP), electrochemical impedance spectroscopy (EIS), linear polarization resistance (LPR), ultraviolet-visible (UV-vis) spectrophotometry, and surface observation methods. The influence of solution temperature on the performance of MPC and MPC + KI is also investigated. Results obtained indicate that the optimum concentration of MPC in 1.0 M HCl and H2SO4 solutions is 500 and 50 mg/L, respectively. The maximum inhibition at the optimum concentrations of MPC in HCl and H2SO4 solutions at 25 degrees C is 46 and 23%, respectively. Addition of 3 mM KI to 500 mg/L MPC in HCl solution and to 50 mg/L MPC in H2SO4 solution at 25 degrees C raised the inhibition efficiency to 86 and 89%, respectively. Inhibition efficiency of MPC and MPC + KI increases with rise in solution temperature with MPC + KI inhibition reaching 88 and 91%, respectively in HCl and H2SO4 solutions at 60 degrees C. Both MPC and MPC + KI acted as a mixed-type corrosion inhibitor according to the PDP results. Surface examination results confirm the effectiveness of MPC + KI mixture in retarding low carbon steel corrosion in 1.0 M HCl and H2SO4 solutions. It could be profitable utilizing MPC + KI mixture in the formulation of corrosion inhibitor cocktail for acid cleaning operations.

Automated summary

The inhibition performance of 5-methyl-3-phenylisoxazole-4-carboxylic acid (MPC) alone and in combination with potassium iodide (KI) for low carbon steel in 1.0 M HCl and H2SO4 solutions was studied. Results showed that KI in combination with MPC significantly improved inhibition efficiency, making it suitable for use in acid cleaning operations.