Electrochemistry and Corrosion
Introduction:
Electrochemistry is the branch of chemistry dealing with the relationship between electricity and chemical reactions. Corrosion is the process of deterioration of a material when it is exposed to the environment. Electrochemistry plays a significant role in corrosion, especially in the corrosion of metals.
Key Concepts:
- Electrochemical cells
- Anode, cathode, oxidation, and reduction
- Galvanic corrosion
- Corrosion prevention techniques
Electrochemical Cells:
An electrochemical cell is a system that converts chemical energy to electrical energy. It consists of two electrodes: an anode and a cathode, and an electrolyte in between them. When metal is exposed to the electrolyte, some of the metal ions dissolve into the solution, leading to the formation of metal cations (ion with positive charge). Also, the electrons are transferred between the anode and cathode, leading to the generation of current.
Anode, Cathode, Oxidation, and Reduction:
The anode is the electrode where oxidation occurs, leading to the dissolution of metal anions in the solution. Whereas, the cathode is the electrode where reduction occurs, leading to the deposition of metal cations from the solution. Oxidation is the loss of electrons, whereas reduction is the gain of electrons.
Galvanic Corrosion:
Galvanic corrosion occurs when two different metals or alloys are in contact with each other and exposed to an electrolyte. In this case, one metal acts as anode, and the other metal acts as cathode. The anode electrode will corrode, leading to the formation of metal ions in solution. Meanwhile, the cathode electrode will generate hydrogen, leading to the depletion of oxygen in solution. This imbalance leads to a localized area with a high concentration of metal ions, which can cause pitting and cracking.
Corrosion Prevention Techniques:
- Coatings and Paints: Applying a barrier between the metal and the environment can prevent corrosion, such as painting or coating the metal with a protective layer.
- Cathodic Protection: Applying an external electrical current to the metal, turning it into the cathode, preventing the metal from anodic dissolution.
- Corrosion Resistant Alloys: Using alloys with higher resistance to corrosion, such as stainless steel.
- Environmental Controls: Reducing the exposure to corrosive environments, such as using salt-resistant materials in marine applications.
References for Further Learning:
- Bard, A. J., Parsons, R., & Jordan, J. (2010). Electrochemical methods: fundamentals and applications. John Wiley & Sons.
- Fontana, M. G., & Greene, N. D. (1988). Corrosion engineering. McGraw-Hill Education.
- ASTM International. (2011). Standard Practice for Expected Service Life for Corrosion Protection of Hot-Dip Galvanized Steel Products. ASTM Standard A123.
- Heyn, A. G. (1971). The corrosion protection of metals by organic coatings. Progress in organic coatings, 1(2), 125-168.
