Kinetic and Thermodynamic Studies of Corrosion Inhibition of Mild Steel Using Plant Extracts

CHAPTER ONE

1.1 Background to the Study

Corrosion is a major problem affecting metals and alloys, especially mild steel. It leads to structural failures, economic losses, and environmental hazards. Chemical inhibitors can reduce corrosion, but many are toxic and expensive. Recently, natural plant extracts have gained interest as eco-friendly corrosion inhibitors due to their availability, low cost, and biodegradability (Okafor et al., 2022).

Plant extracts contain compounds such as alkaloids, flavonoids, and tannins that adsorb onto metal surfaces, forming a protective film. This layer prevents the diffusion of corrosive ions and reduces the corrosion rate (Singh & Yadav, 2021). Studying the kinetics and thermodynamics of this process helps to explain the mechanism of inhibition and adsorption behavior.

This research examines the corrosion inhibition efficiency of selected plant extracts on mild steel in acidic environments and evaluates their kinetic and thermodynamic parameters.

1.2 Statement of the Problem

Corrosion reduces the lifespan of steel structures and increases maintenance costs. Synthetic inhibitors offer protection but harm the environment. Plant-based inhibitors are promising alternatives, but more studies are needed to understand their thermodynamic and kinetic behavior in various conditions. This study seeks to provide this understanding and identify efficient natural inhibitors.

1.3 Aim and Objectives of the Study

Aim:
To investigate the kinetic and thermodynamic parameters of corrosion inhibition of mild steel using plant extracts.

Objectives:

1. To extract and prepare natural inhibitors from selected plants.

2. To study their inhibitory effects on mild steel corrosion in acidic media.

3. To determine the adsorption, kinetic, and thermodynamic parameters of inhibition.

4. To evaluate the efficiency of inhibition under different experimental conditions.

1.4 Research Questions

1. How do plant extracts inhibit the corrosion of mild steel?

2. What are the kinetic and thermodynamic characteristics of the inhibition process?

3. How does temperature affect the inhibition efficiency?

4. Which extract shows the best performance?

1.5 Significance of the Study

This study will support the development of green corrosion inhibitors that are safe, affordable, and effective. The results will provide a scientific basis for using plant extracts in industrial corrosion control. The findings will also promote sustainable engineering and environmental protection.

1.6 Scope of the Study

The study focuses on the corrosion inhibition of mild steel in acidic media using selected plant extracts. It covers kinetic and thermodynamic analysis but excludes the use of synthetic inhibitors or alloy materials.

1.7 Operational Definition of Terms

• Corrosion: The gradual destruction of metals by chemical or electrochemical reactions.

• Inhibitor: A substance that decreases the rate of corrosion.

• Kinetics: The study of reaction rates and mechanisms.

• Thermodynamics: The study of heat and energy changes during reactions.

• Adsorption: The process by which molecules adhere to a solid surface.