Question

Aqueous corrosion of metals generally involves

• A. electrochemical reactions
• B. mechanical wear
• C. thermal decomposition
• D. magnetic interaction

Hint:

For aqueous corrosion to occur, all four elements of the electrochemical cell (anode, cathode, electrolyte, and metallic path) must be present. Removing any one stops the corrosion.

Answer 1

The Correct Option is A

Step 1: Understanding the Question:
The question asks about the fundamental chemical mechanism underlying the aqueous (wet) corrosion of metals.

Step 2: Key Formula or Approach:
Aqueous corrosion requires the operation of an electrochemical cell, consisting of:
1. Anodic reaction (oxidation):
\[ M \rightarrow M^{n+} + n e^- \]
2. Cathodic reaction (reduction):
\[ 2H^+ + 2e^- \rightarrow H_2 \quad (\text{in acidic solutions}) \]
or
\[ O_2 + 2H_2O + 4e^- \rightarrow 4OH^- \quad (\text{in neutral or basic solutions}) \]

Step 3: Detailed Explanation:

• Electrochemical Mechanism: Aqueous corrosion is fundamentally an electrochemical process involving the transfer of electrons.
It requires four vital components: an anode (where the metal dissolves), a cathode (where a reduction reaction occurs), an electrical path through the metal, and an ionic path through the electrolyte (water containing dissolved salts/gases).

• Comparison with Other Options:
-

Mechanical wear (Option B) is physical degradation. Though it can synergize with corrosion (erosion-corrosion), it is not the mechanism of chemical attack.
-

Thermal decomposition (Option C) involves breakdown of compounds due to heat, which is unrelated to liquid-phase wet corrosion.
-

Magnetic interaction (Option D) has no direct role in standard metal corrosion pathways.


Step 4: Final Answer:
Thus, aqueous corrosion of metals involves electrochemical reactions, which corresponds to Option (A).