Research on the inhibition mechanism of tetraphenylporphyrin on AZ91D magnesium alloy

5,10,15,20-Tetraphenylporphyrin (TPP) is synthesized and its inhibition effect on AZ91D magnesium alloy in 0.05 wt.% NaCl solution is studied. Electrochemical measurement and immersion corrosion test results indicate that the inhibition efficiency of TPP reaches 90%. SEM, FT-IR, ultraviolet–visible absorption spectrum (UV), fluorescent spectrometry and XPS analyses suggest that TPP molecules can chelate with Mg via their N atoms to form a TPP–Mg complex, which can precipitate as a film on AZ91D alloy. The precipitated TPP–Mg reduces the porosity of the original Mg(OH)2 surface film and retards the dissolution of the Mg alloy.

► Environment-friendly tetraphenylporphyrin is synthesized in the lab.
► The tetraphenylporphyrin can efficiently inhibit AZ91D corrosion.
► The inhibitor chelates with Mg ions to form a film retarding Mg dissolution.