📄 chemistry

Potato Peel Extract as an ecologically conscious Inhibitor for corrosion of A283 Carbon Steel in Hydrochloric Acid: Experimental and Theoretical Perspectives

This study demonstrates that potato peel extract acts as an effective, eco-friendly mixed-type corrosion inhibitor for A283 carbon steel in hydrochloric acid by forming a protective adsorbed film, with its performance validated through comprehensive experimental characterization and theoretical analysis identifying petunidin and chlorogenic acid as the primary active constituents.

Original authors: Metwally Abdallah, Omar A. Hazazi, Dina Walid, Salih S. Al-Juaid, Doaa F. Seyam Seyam, Ali Y. El-Etre, Elsayed M. Mabrouk, Nahed Fouad

Published 2026-06-27

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CC BY 4.0

Original authors: Metwally Abdallah, Omar A. Hazazi, Dina Walid, Salih S. Al-Juaid, Doaa F. Seyam Seyam, Ali Y. El-Etre, Elsayed M. Mabrouk, Nahed Fouad

Original paper licensed under CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/). ✨ This is an AI-generated explanation of the paper below. It is not written or endorsed by the authors. For technical accuracy, refer to the original paper. Read full disclaimer

Imagine you have a very strong, hungry acid (hydrochloric acid) that wants to eat away at your steel pipes or tanks. This is a common problem in industries like oil and gas. Usually, to stop the acid from eating the steel, scientists add special chemicals called "inhibitors." But many of these traditional inhibitors are like toxic poisons—they work well, but they hurt the environment and people.

This paper introduces a new, eco-friendly hero: Potato Peel Extract. Yes, the skin you throw away after peeling a potato!

Here is the story of how the researchers tested this "green" solution, explained in simple terms:

1. The Recipe: Making the "Anti-Acid" Potion

The researchers didn't just throw potato skins in a jar. They took the peels, washed them, dried them in the sun, and then boiled them in alcohol (ethanol) for three hours. This process pulled out the "good stuff" inside the skins—natural chemicals like chlorogenic acid and petunidin (which gives potatoes their purple color). They dried this mixture into a white powder, ready to be tested.

2. The Test: The "Shield" Experiment

They took pieces of carbon steel (the kind used in construction and pipelines) and put them in a strong acid bath.

The Control Group: Some steel was left alone in the acid. It got eaten away quickly, turning into rust and pitting.
The Test Group: Other steel was put in the acid with the potato peel powder dissolved in it.

The Result: The potato peel powder acted like a force field. The more powder they added, the better the steel was protected. At the highest concentration, the potato peel stopped about 98% of the corrosion. It was so effective that even after a week, the steel looked much healthier than the unprotected pieces.

3. How It Works: The "Molecular Blanket"

Why did the potato skins work?
Think of the steel surface as a crowded dance floor. The acid molecules are aggressive dancers trying to push the steel atoms off the floor.

The Potato Molecules: The active chemicals in the potato peel are like a thick, sticky blanket. They float in the acid and quickly jump onto the steel surface.
The Shield: Once they land, they spread out and cover the steel, forming a protective layer. This layer blocks the acid from touching the metal.
The Mechanism: The paper explains that these molecules stick to the steel through a gentle "hug" called physical adsorption. They don't form a permanent, unbreakable bond (like glue); instead, they sit on top, held by electrical attraction. This is why the protection works best when it's cooler; if you heat it up too much, the molecules get too energetic and jump off the steel, letting the acid back in.

4. The Detective Work: Looking Under the Microscope

The researchers used powerful microscopes (SEM) to look at the steel surfaces.

Without Potato Peel: The steel looked like a war zone—full of deep pits, cracks, and rough holes where the acid had gnawed it away.
With Potato Peel: The steel looked smooth and calm, like a freshly paved road. The "blanket" had successfully kept the acid away.

5. The Computer Simulation: The "Virtual Lab"

To understand exactly which part of the potato skin was doing the heavy lifting, the scientists used supercomputers to simulate the molecules.

They found that two specific ingredients, Petunidin and Chlorogenic Acid, were the "superheroes" of the mix.
These molecules are like magnets that love to stick to iron. They have special parts (electrons) that they can easily give away to the steel, making them stick very well and cover the surface effectively.

6. The Bottom Line

The paper concludes that potato peel extract is a safe, cheap, and environmentally friendly way to stop steel from rusting in acid.

It works by covering the steel in a protective layer.
It works best when there is a lot of the extract and when the temperature is not too hot.
It is a "mixed-type" inhibitor, meaning it stops both the chemical reactions that dissolve the metal and the reactions that create gas bubbles.

In short: Instead of throwing away potato skins, this research suggests we could use them to save our steel infrastructure from being eaten alive by acid, all while keeping the environment safe from toxic chemicals.

Technical Summary: Potato Peel Extract as an Eco-Friendly Corrosion Inhibitor for A283 Carbon Steel

Problem Statement
Carbon steel (specifically A283 grade C) is extensively utilized in critical industrial sectors such as oil and gas pipelines, construction, and storage tanks. To maintain these structures, hydrochloric acid (HCl) is commonly employed for pickling to remove rust. However, this process exposes the steel to aggressive chloride ions, leading to severe substrate corrosion. While organic inhibitors containing heteroatoms are effective, many are toxic and environmentally hazardous. Consequently, there is a strategic need to develop eco-friendly, biodegradable, and low-cost alternatives, such as plant extracts, that can effectively mitigate corrosion without compromising safety or economic feasibility.

Methodology
The study investigated the efficacy of potato peel extract as a corrosion inhibitor for A283 carbon steel in a 2.0 M HCl solution. The research employed a multi-faceted approach combining experimental, surface analytical, and theoretical perspectives:

Extraction and Characterization: Potato peels were washed, sun-dried, and refluxed in ethanol to obtain an extract. The active constituents were identified using FT-IR, ¹H NMR, ¹³C NMR, and Mass Spectrometry. Key bioactive components identified included α-chaconine, chlorogenic acid, caffeic acid, petunidin, gallic acid, and quercetin.
Experimental Corrosion Measurements:
- Weight Loss (WL): Steel coupons were immersed in HCl with varying extract concentrations (10–500 ppm) over 7 days at 25°C to determine corrosion rates and inhibition efficiency.
- Electrochemical Techniques: Potentiodynamic Polarization (PDP) and Electrochemical Impedance Spectroscopy (EIS) were conducted at temperatures ranging from 25°C to 50°C. These tests measured corrosion current density, corrosion potential, charge transfer resistance, and double-layer capacitance.
Surface Analysis: Scanning Electron Microscopy (SEM) was used to visualize the surface morphology of the steel after immersion in uninhibited and inhibited solutions.
Theoretical Simulations: Density Functional Theory (DFT) calculations (B3LYP/6-311G(d,p)) were performed to determine quantum chemical parameters (HOMO, LUMO, energy gap, electronegativity, hardness). Additionally, Monte Carlo simulations were conducted to model the adsorption behavior of the active molecules on an Fe (110) surface in a solvent environment.

Key Results

Inhibition Efficiency: The potato peel extract demonstrated significant corrosion inhibition. Efficiency increased with higher extract concentrations, reaching a maximum of 97.88% at 500 ppm (PDP data) and 92.8% at 25°C (WL data). Conversely, inhibition efficiency decreased as temperature increased, suggesting a physisorption mechanism.
Inhibition Type: PDP analysis indicated that the extract acts as a mixed-type inhibitor, suppressing both anodic metal dissolution and cathodic hydrogen evolution reactions without significantly altering the corrosion mechanism. The shift in corrosion potential ( $E_{corr}$ ) was minimal (< 34 mV).
Adsorption Mechanism: The adsorption of the extract onto the steel surface followed the Langmuir adsorption isotherm. The calculated standard free energy of adsorption ( $\Delta G^\circ_{ads}$ ) was -28.41 kJ mol⁻¹. This value, being between -20 and -40 kJ mol⁻¹, indicates that the inhibition is primarily driven by physical adsorption (electrostatic interactions), with possible minor contributions from chemical adsorption.
Thermodynamics: The corrosion process was found to be endothermic ( $\Delta H^* > 0$ ). The presence of the inhibitor increased the activation energy ( $E_a$ ) from 27.12 kJ mol⁻¹ (blank) to 45.58 kJ mol⁻¹ (inhibited), confirming that the adsorbed layer creates an energy barrier that hinders the corrosion reaction.
Surface Morphology: SEM images revealed that the uninhibited steel surface was severely degraded with pits and cracks. In contrast, the surface exposed to 500 ppm extract remained smooth and homogeneous, confirming the formation of a protective film.
Theoretical Insights: DFT and Monte Carlo simulations identified petunidin and chlorogenic acid as the most potent components due to their high electron-donating capacity ( $\Delta N$ ) and the lowest HOMO-LUMO energy gaps. The simulations showed these molecules adsorb in a nearly horizontal orientation, maximizing surface coverage. The calculated adsorption energies were highly negative (ranging from -77.48 to -353.59 kcal/mol), supporting spontaneous adsorption.

Significance and Claims
The authors claim that potato peel extract serves as a safe, affordable, and environmentally conscious alternative to traditional toxic corrosion inhibitors. The study successfully validates that the extract's efficacy stems from the spontaneous adsorption of its bioactive constituents (rich in heteroatoms like N and O, and $\pi$ -electron systems) onto the carbon steel surface. This adsorption forms a protective monolayer that isolates the metal from the aggressive acidic medium.

The paper emphasizes that the combination of experimental data and theoretical modeling provides a comprehensive understanding of the inhibition mechanism. Specifically, the identification of petunidin and chlorogenic acid as the primary active agents offers insight into the molecular basis of the extract's performance. The work contributes to the development of sustainable corrosion control techniques by utilizing agricultural waste (potato peels) to protect industrial infrastructure, aligning with green chemistry principles.