Evaluation of Polyesters as Effective Corrosion Mitigators for Mild Steel in a Pool of Acidic Environments: A Comparative Approach

The extent of minimising the metal dissolution in industrial sectors is nowadays becoming a challenging task which without proper attention may lead to lack in safety of person, environment as well the life span of machineries. In order to overcome the limitation and as a motto of revealing the facts involved in protecting the mild steel specimens in a pool of various acidic environment like 0.5 M H₂SO₄, 1 M HCl and 0.3 M H₃PO₄, the present study has been undertaken. Polyesters namely Poly (glycerol azealate) (PGAZ) and 4-(1-(4-methoxyphenyl) cyclohexyl)phenyl 9-oxodecanoate (MPOD) were synthesised and characterised by Fourier transform Infra-red spectroscopy (FT-IR) and ¹H and ¹³C Nuclear magnetic resonance spectroscopy (NMR). Differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA) thermograms evidenced its amorphous nature and thermal stability in which the glass transition temperature was less due to the flexibility in PGAZ and more due to rigidity in MPOD. From the weight loss method, the highest inhibition efficiency of 92.22% was obtained for MPOD in 1 M HCl solution. It is additionally evident from the electrochemical measurements that MPOD has attained maximum inhibition efficiency of 90.11% (1 M HCl). Electrochemical and non-electrochemical studies were in good agreement with each other stating the order of inhibition efficiency as HCl > H₂SO₄ > H₃PO₄ where mixed type of inhibition was revealed.