Table of Contents
Half-cell potential measurements are a common method used to estimate the corrosion rate of metal structures. This technique involves measuring the electrical potential difference between a metal surface and a reference electrode. The data obtained can help assess the likelihood and severity of corrosion in various environments.
Principle of Half-Cell Potential Measurement
The method is based on electrochemical principles. When a metal is exposed to an electrolyte, it develops a potential relative to a reference electrode. This potential, known as the corrosion potential or half-cell potential, indicates the metal’s tendency to corrode. More negative potentials typically suggest higher corrosion activity.
Procedure for Measurement
To perform measurements, a reference electrode such as a copper/copper sulfate or silver/silver chloride electrode is placed in contact with the environment near the metal surface. A voltmeter records the potential difference between the reference electrode and the metal. Multiple readings across different areas provide a comprehensive corrosion profile.
Estimating Corrosion Rate
The measured potential can be correlated with corrosion rates using empirical charts or models. Generally, potentials more negative than -350 mV vs. a copper/copper sulfate electrode indicate active corrosion. Conversely, potentials above -200 mV suggest passive or non-corrosive conditions.
- Corrosion potential measurement
- Reference electrode placement
- Multiple site testing
- Data interpretation using empirical models