Abstract
Objectives: To examine the thermodynamics and kinetics of Alpinia officinarum’s (AO) inhibitory response on carbon steel (CS) corrosion in well water. Weight-loss (WL), potentiodynamic polarization (PDP), electrochemical impedance spectroscopy (EIS) methods and various pH levels are utilized to calculate the inhibition efficiency (IE) and corrosion rate (CR). Methods: WL and PDP and EIS techniques were performed to assess the corrosion inhibition and adsorption capacity of an ethanolic extract of AO leaves on the CS in well water. SEM and AFM techniques were analyzed to explore the creation of a safe layer onto the CS surface. Findings: The maximum IE of 93% is attained from the WL study at 303K. For the AO-Zn2+ system, when the temperature is increased from 303K to 343K, CR is also increased and IE is decreased. Arrhenius plots show a straight line, indicating the effect of temperatures on the CR. PDP findings indicate that the AO-Zn2 + system performs as a mixed-type inhibitor. The ΔGads values are less than -20KJ/mol, signifying that physisorption on the CS surface has occurred. The positive values of ΔH demonstrate AO leaves are adsorbing endothermically onto CS surface. The high adsorption of ethanolic extract of AO leaves on the CS surface in well water is reflected by positive activation energy values. Langmuir model is the best fit for the adsorption of ethanolic extract of AO leaves. Novelty: The nature of the adsorption process on the CS surface in well water was investigated by thermodynamic parameters (ΔGads, qads, ΔSads, ΔH) and activation energy (Ea) using a combined inhibitor (AO-Zn2+) system. The regression coefficient (R2) values were calculated using the various adsorption isotherms to determine the pattern of inhibition on the CS surface. The F-test and synergism parameters were used to establish the synergistic inhibition (SI) impact existing between ethanolic extract of AO leaves and Zn2+. KeywordsGreen corrosion inhibitor, thermodynamics, kinetics, PDP, EIS, SEM, AFM, FTIR, adsorption models, synergism parameters
Highlights
InroductionCorrosion is a natural chemical process of transforming metal and alloy structures into chemically stable oxides, hydroxides and sulphides [1]
Weight-loss study was carried out for carbon steel (CS) specimens immersed in well water for one day in the absence and presence of different concentrations of Zn2+ ions (10, 20 and 30ppm) and ethanolic extract of Alpinia officinarum (AO) leaves
Corrosion kinetic and adsorption thermodynamic effect for AO leaves extract onto CS surface in well-water were investigated using WL measurement
Summary
Corrosion is a natural chemical process of transforming metal and alloy structures into chemically stable oxides, hydroxides and sulphides [1]. The most prominent study in the recent times has been the hunt for environmentally safe, degradable, and abundantly present inhibitors. Natural elements such as fruits, leaves and flowers have been shown to effective corrosion inhibitors[13]. Plant extract has been reported as one of the most cost-effective, degradable, water soluble and environmentally friendly metal corrosion inhibitors. It is non-toxic, pure and readily available [14,15,16,17,18,19]. The corrosion inhibition performance of CS is discussed by green inhibitor-Zn2+ system [19,20,21,22,23,24,25]
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