Principles of Corrosion Kinetics

Module Five of CCE 281 Corrosion: Impact, Principles, and Practical Solutions

Lesson Objectives

•  Explain the polarization components that control the corrosion current

•  Describe the impact of these polarization components on corrosion rates

•  Examine a typical polarization diagram in relation to cathodic protection

•  Discuss the effect of the ohmic drop on the corrosion current

Table of Contents

•  Introduction

•  What is an overpotential?

•  Activation polarization

•  Concentration polarization

•  Ohmic drop

  •  Water Resistivity Measurement

  •  Soil Resistivity Measurements

•  Graphical Presentation of Kinetic Data (Evans Diagrams)

  •  Activation controlled processes

  •  Concentration controlled processes

Introduction

Thermodynamic principles can help explain a corrosion situation in terms of the stability of chemical species and reactions associated with corrosion processes. However, these principles cannot be used to predict corrosion currents or corrosion rates. In reality, the polarization effects control the balancing cathodic and anodic currents that are integrated components of corrosion processes. (reference)

Given the electrochemical nature of corrosion processes it is not surprising to see that measurements and control methods based on electrochemical principles are so extensively used across the whole spectrum of corrosion science and engineering.

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