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Difficulty: MediumCorrosion of Metals and Prevention Methods

Fill in the missing terms to complete the statement describing the electrochemical roles of different regions during the rusting of iron.

Answer:In the electrochemical mechanism of rusting, the site on the iron surface where metallic iron is oxidized to iron(II) ions functions as the 【anode】, while the region exposed to moisture and oxygen where reduction occurs acts as the 【cathode】.

Answer

The site where metallic iron is oxidized functions as the anode, and the region where reduction occurs acts as the cathode.
During the rusting of iron, a micro-galvanic cell is established on the surface of the metal. The region where iron loses electrons to become Fe2+Fe^{2+} ions undergoes oxidation and therefore functions as the anode. The oxygen-rich droplet region where electrons are consumed to reduce oxygen to OH−OH^- ions functions as the cathode.

Step-by-Step Solution

1
Identify the region of oxidation during rusting.
Iron atoms lose electrons (Fe(s)→Fe2+(aq)+2e−Fe(s) \rightarrow Fe^{2+}(aq) + 2e^-), which corresponds to oxidation.
By electrochemical definition, oxidation always occurs at the anode.
2
Identify the region of reduction during rusting.
Dissolved oxygen accepts electrons in the presence of water (O2(g)+2H2O(l)+4e−→4OH−(aq)O_2(g) + 2H_2O(l) + 4e^- \rightarrow 4OH^-(aq)), which corresponds to reduction.
By electrochemical definition, reduction always takes place at the cathode.

Key Concept

Electrochemical mechanism of metallic corrosion
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Topics

Corrosion of Metals and Prevention Methods

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