Galvanic corrosion

Definition

Galvanic corrosion is an electrochemical process where one metal corrodes preferentially when in electrical contact with another metal in the presence of an electrolyte. This type of corrosion occurs due to the difference in electrode potentials between the two metals, leading to the more anodic metal deteriorating faster. Understanding galvanic corrosion is crucial for preventing material degradation and ensuring the longevity of metal structures.

5 Must Know Facts For Your Next Test

1. Galvanic corrosion typically occurs when two dissimilar metals are in contact with each other in a moist environment, such as water or soil.
2. The metal with a higher electrode potential becomes the cathode and is protected, while the metal with a lower electrode potential acts as the anode and corrodes more rapidly.
3. Common examples of galvanic corrosion include steel bolts corroding when used with aluminum components in marine environments.
4. Preventative measures against galvanic corrosion include using insulating materials between different metals and applying protective coatings.
5. The Nernst equation can be used to predict the voltage developed between two metals, helping to assess the risk of galvanic corrosion in specific situations.

Review Questions

• How does the difference in electrode potentials between two metals lead to galvanic corrosion?
  • Galvanic corrosion occurs when two dissimilar metals are electrically connected in an electrolyte, creating a galvanic cell. The metal with a lower electrode potential acts as the anode and undergoes oxidation, losing electrons and corroding faster. In contrast, the metal with a higher electrode potential becomes the cathode, gaining electrons and remaining relatively protected. This difference in behavior between the two metals is what drives the process of galvanic corrosion.
• Discuss some practical methods to prevent galvanic corrosion in engineering applications involving dissimilar metals.
  • To prevent galvanic corrosion, several methods can be employed, including using insulating materials or gaskets to separate dissimilar metals and minimize direct contact. Additionally, applying protective coatings such as paints or anodizing can create a barrier against electrolytes. Cathodic protection techniques, like attaching a sacrificial anode made of a more anodic material, can also be used to divert corrosion away from critical components. These strategies help mitigate the risk of galvanic corrosion and prolong the lifespan of metal structures.
• Evaluate how understanding galvanic corrosion contributes to better material selection and design in engineering projects.
  • Understanding galvanic corrosion plays a vital role in material selection and design for engineering projects, particularly those involving multiple metals exposed to corrosive environments. By evaluating electrode potentials and their interactions, engineers can choose compatible materials that minimize corrosion risks. Knowledge of galvanic behavior allows for informed decisions on protective measures, such as coatings or isolation techniques. This proactive approach not only enhances durability and safety but also reduces maintenance costs and extends the service life of structures and components.

Related terms

anode: The electrode in an electrochemical cell where oxidation occurs, leading to the loss of electrons and potential corrosion.

cathode:

The electrode in an electrochemical cell where reduction occurs, typically receiving electrons from the anode.

electrolyte:

A substance that produces an electrically conducting solution when dissolved in a solvent, facilitating the flow of ions necessary for galvanic processes.