Poly(glycerol pimelate) polyester as moderate mild steel protector in 0.5 M H₂SO₄: justified from electrochemical approach and XPS investigation

Abstract

This work reports a facile synthesis of linear long chain aliphatic polyester, namely poly(glycerol pimelate) polyester (PGP) characterised by Fourier transform infrared spectroscopy (FTIR) and Nuclear magnetic resonance spectroscopy (¹H and ¹³C NMR). Thermal response of PGP was studied using Thermo gravimetric analysis (TGA) and Differential scanning calorimetry (DSC). Glass transition temperature (T_g) of 117 °C and thermal stability up to 290 °C was noticed from DSC and TGA analysis. As a potential application, the capability and extent of retarding the mild steel dissolution in 0.5 M H₂SO₄ medium rendered by the synthesised PGP was analysed by electrochemical and non-electrochemical methods. Weight loss measurements carried out at room temperature showed decreased corrosion rate with concentration (10, 50, 100, 500 and 1000 ppm) resulting in a moderate inhibition efficiency of 61.60% at 1000 ppm. Decreased inhibition efficiency was noticed on increasing the temperature from 303 K-333K. Various parameters were derived to understand the mode of adsorption. Increased charge transfer resistance (R_ct) from electrochemical impedance method (EIS) and decreased corrosion current density (I_corr) from potentiodynamic polarisation technique on increasing the concentration was in good agreement with weight loss measurements. Suppression of metal dissolution by the formation of film on the metal surface was additionally supported by X-ray diffraction studies (XRD), scanning electron microscopy (SEM) and Energy dispersive spectroscopy (EDS) followed by Atomic force microscopy (AFM). X-ray photoelectron spectroscopy (XPS) revealed the same with a detailed insight of adsorption of inhibitor on the metal surface.

Highlights

• This paper explores the following highlights:

• Low cost and facile synthesis of polyester.

• Controversy result of moderate inhibition efficiency has been justified.

• Potentiodynamic polarisation studies revealed mixed type of inhibition.

• Morphological studies like XPS predicted detailed insight of adsorption.

Keywords:

• Poly(glycerol pimelate) polyester
• thermal analysis
• aggressive medium
• moderate efficiency
• corrosion rate
• XPS

Disclosure statement

No potential conflict of interest was reported by the authors.