Galvanic Corrosion Process

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Questions and Answers

What is galvanic corrosion?

The corrosion that occurs when metals are not in contact with each other.

The corrosion that occurs when two similar metals are surrounded by an electrolyte.

The corrosion that occurs when two dissimilar metals are surrounded by an electrolyte. (correct)

The corrosion that occurs when metals are not surrounded by an electrolyte.

What causes electrons to flow in galvanic corrosion?

The difference of electrochemical potential between dissimilar metals. (correct)

The presence of stress on the metal.

The presence of imperfections on the metal surface.

The difference in crystal sizes on the metal.

What can cause galvanic corrosion even in a single type of metal?

Surface imperfections

Different crystal sizes

Crystal misalignment

All of the above (correct)

What is the role of stress in stress corrosion cracking?

It makes the area under stress anodic to the rest of the metal. Signup and view all the answers

What is the electromotive series?

A series that lists the electrochemical potential of various metals in descending order. Signup and view all the answers

What is the role of soluble metal ions in galvanic corrosion?

They enter solution with the electrolyte and cause the anodic metal to waste away. Signup and view all the answers

How does a scratch or a dent contribute to galvanic corrosion?

It causes one location to be more anodic, leading to corrosion Signup and view all the answers

What happens when two metals with a greater potential difference are coupled in a galvanic cell?

The rate of corrosion is greater Signup and view all the answers

What do noble metals listed at the top of Table 2 do in a galvanic cell?

Receive electrons from anodic metals Signup and view all the answers

In a zinc-copper galvanic cell, which metal acts as the cathode?

Copper (Cu) Signup and view all the answers

What forms bubbles of H2 gas in a zinc-copper galvanic cell?

H+ ions Signup and view all the answers

What is a sacrificial anode used for?

To prevent galvanic corrosion Signup and view all the answers

What is recommended to minimize galvanic corrosion when joining different alloys?

Using electrically insulated dissimilar metals Signup and view all the answers

What is the role of sacrificial anodes in preventing galvanic corrosion?

They corrode instead of the protected cathodic materials Signup and view all the answers

In a zinc-copper galvanic cell, which metal acts as the anode?

Zinc Signup and view all the answers

What do noble metals listed at the top of Table 2 do in a galvanic cell?

Receive electrons from anodic metals Signup and view all the answers

What causes electrons to flow in galvanic corrosion?

The potential difference between the metals Signup and view all the answers

What happens when two metals with a greater potential difference are coupled in a galvanic cell?

The rate of corrosion increases Signup and view all the answers

What forms bubbles of H2 gas in a zinc-copper galvanic cell?

$H+$ ions combining with electrolyte Signup and view all the answers

What is recommended to minimize galvanic corrosion when joining different alloys?

Using materials with similar electrochemical potential Signup and view all the answers

Study Notes

Galvanic Corrosion

Galvanic corrosion occurs when two dissimilar metals with a potential difference are in contact in the presence of an electrolyte, resulting in the flow of electrons.
The flow of electrons in galvanic corrosion is caused by the difference in electrode potential between the two metals.

Electromotive Series

The electromotive series is a ranking of metals based on their electrode potential, with noble metals having a higher potential and more reactive metals having a lower potential.

Role of Soluble Metal Ions

Soluble metal ions, such as copper ions, can accelerate galvanic corrosion by increasing the conductivity of the electrolyte.

Effect of Scratches or Dents

Scratches or dents on a metal surface can create a localized galvanic cell, leading to accelerated corrosion.

Galvanic Cell Reaction

When two metals with a greater potential difference are coupled in a galvanic cell, electrons flow from the more reactive metal (anode) to the less reactive metal (cathode).
In a zinc-copper galvanic cell, zinc acts as the anode and copper acts as the cathode.
Hydrogen gas is formed at the cathode, causing bubbles to form.

Noble Metals

Noble metals, listed at the top of the electromotive series, act as cathodes in a galvanic cell, attracting electrons.

Prevention of Galvanic Corrosion

To minimize galvanic corrosion when joining different alloys, it is recommended to use a sacrificial anode, which corrodes in place of the more noble metal.
Sacrificial anodes, such as zinc, are used to protect more noble metals from corrosion by corroding themselves instead.
Stress can contribute to galvanic corrosion by creating micro-cracks in the metal, allowing electrolytes to penetrate and accelerate corrosion.

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Description

Test your knowledge about the process of galvanic corrosion, which occurs when two dissimilar metals come into contact with an electrolyte. Understand the electrochemical potential and the flow of electrons between the anode and cathode.