Investigating the synergistic effect of iodide ion and Michelia alba leaf extract on carbon steel in 0.5 M H2SO4

The study examined the inhibitory effect of Michelia alba leaf extract (MALE) on carbon steel (CS) in 0.5 M H2SO4 solution. Furthermore, the investigation explored the effect of KI to enhance the protection provided by MALE. The study demonstrates that both MALE and KI have corrosion inhibiting properties on CS in acidic solutions. However, when MALE and KI are combined, they exhibit a greater inhibitory effect. Corrosion inhibition efficiency was limited to 86.55 % with 400 mg/L MALE. The maximum corrosion inhibition efficiency was 51.84 % when 400 mg/L KI was used alone. However, when 800 mg/L MALE was combined with 400 mg/L KI in 0.5 M H2SO4 solution, the efficiency increased to 95.02 %. This increase can be attributed to the synergistic effect between MALE and KI. The SEM and XPS results further confirmed that the addition of KI could be more effective in preventing the corrosion of CS. The theoretical calculations demonstrate that constituents found in the extract, which are rich in hydroxyl groups, benzene rings, N and S atoms have a higher probability of adsorption onto the CS surface in parallel, thereby increasing the efficiency of corrosion inhibition significantly.