Electrochemical and molecular simulation studies on the corrosion inhibition of 5,10,15,20-tetraphenylporphyrin adlayers on iron surface

5,10,15,20-Tetraphenylporphyrin (TPP) was synthesized and self-assembled on iron surface to form adlayers. Some surface analysis techniques such as XPS, FT-IR and SEM were performed to characterize the adlayers. The corrosion inhibition ability was investigated by using the technique of electrochemical impedance spectroscopy (EIS) and polarization curves in 0.5 M H₂SO₄. Results showed that the presence of the porphyrin adlayers was able to protect iron from corrosion effectively and longer immersion time would lead to better inhibition performance. In addition, molecular simulation studies were applied to optimize the adsorption structures of TPP molecules on iron surface. Calculated results indicated that the middle macrocycle of the TPP molecules assumed a nearly flat orientation with respect to the iron surface and the four centrosymmetric benzene rings were tilted by 44.8° and 58.8° because of the steric hindrance effect.