Effects of corrosion inhibition with xanthines in gray cast iron protection with Paraloid B-72 in a saline medium

The effect of caffeine and theophylline concentrations as corrosion inhibitors for grey cast iron, in combination with a coating (Paraloid B-72) in a saline medium was evaluated through electrochemical impedance spectroscopy. Both compounds showed good results regarding to the inhibiting capability efficiency. Caffeine showed inhibition against corrosion in high concentrations and theophylline did so in low concentrations, thus exerting a synergic effect with the Paraloid B-72. The immersion time effect was also studied in both compounds. Results showed that 50 mg/m2 of theophylline + paraloid B-72, presented the most stable coating in the metal surface. By means of SEM-EDS, it was confirmed that the presence of the inhibitors on the metallic surface diminished the corrosive process as a result of the absence of chloride ions. Finally, Fourier transformed infrared spectroscopy (FT-IR) was employed to demonstrate the chemical interactions between the theophylline or caffeine and Paraloid B-72 functional groups.

Automated summary

Caffeine and theophylline act as corrosion inhibitors for grey cast iron when combined with the coating Paraloid B-72 in a saline medium, showing good inhibiting capability efficiency and exerting a synergic effect. Theophylline in combination with Paraloid B-72 presents the most stable coating on the metal surface, reducing the corrosive process effectively.