Galvanic corrosion

Definition

Galvanic corrosion occurs when two different metals are in electrical contact in the presence of an electrolyte, causing one metal to corrode preferentially over the other. This type of corrosion is driven by the electrochemical potential difference between the metals, leading to a flow of electrons that results in material degradation. Understanding this phenomenon is crucial in managing corrosive wear, particularly in applications where dissimilar metals are used together.

5 Must Know Facts For Your Next Test

1. Galvanic corrosion is accelerated when metals with significant differences in their electrochemical potential are coupled together.
2. In a galvanic couple, the metal with a higher potential acts as the cathode and is protected, while the lower potential metal acts as the anode and corrodes.
3. Common examples of galvanic corrosion can be seen in marine environments where aluminum and stainless steel are used together.
4. Preventative measures include using insulating materials to separate dissimilar metals or applying protective coatings to reduce exposure to electrolytes.
5. The severity of galvanic corrosion can be influenced by environmental factors like temperature, pH levels, and the presence of salts or pollutants.

Review Questions

• How does the electrochemical potential difference between dissimilar metals lead to galvanic corrosion?
  • The electrochemical potential difference between dissimilar metals creates a driving force for electron flow when they are electrically connected in an electrolyte. The metal with a higher potential acts as the cathode, undergoing reduction, while the one with lower potential becomes the anode and experiences oxidation, leading to its corrosion. This process emphasizes the importance of understanding material pairings in order to prevent excessive wear and failure in engineering applications.
• What are some common strategies used to prevent galvanic corrosion in engineering designs?
  • To prevent galvanic corrosion, engineers often employ several strategies such as isolating dissimilar metals using non-conductive materials or coatings, which inhibit electron flow. Additionally, sacrificial anodes can be used; these are more reactive metals placed intentionally to corrode instead of the protected metal. Regular maintenance and monitoring can also help identify early signs of galvanic corrosion before significant damage occurs.
• Evaluate how galvanic corrosion affects material selection and design considerations in modern engineering applications.
  • Galvanic corrosion significantly influences material selection and design by necessitating careful consideration of electrochemical properties of materials being used together. Engineers must evaluate not only individual material strength but also how they interact with each other in environments where they may contact electrolytes. This assessment leads to designing systems that minimize contact between dissimilar metals or incorporating protective strategies that prolong component life, ultimately affecting cost efficiency and safety.

Related terms

Electrolyte: A substance that produces an electrically conducting solution when dissolved in a solvent, facilitating the flow of ions.

Anode: The electrode in an electrochemical cell where oxidation occurs, leading to corrosion in galvanic corrosion scenarios.

Cathode: The electrode in an electrochemical cell where reduction occurs, playing a crucial role in galvanic corrosion as the metal that is less likely to corrode.