Aluminum is more reactive than iron, yet it is used today for a variety of applications in which iron would corrode (cans, rain gutters,etc). The reason for the corrosion durability
of aluminum is
1. all aluminum products are treated with a plastic coating.
2. aluminum does not undergo oxidation.
3. very unreactive aluminum oxide forms a thin layer on aluminum.
4. aluminum does not react with oxygen.
The correct answer is 3.
The reason for the corrosion durability of aluminum is that a very unreactive aluminum oxide forms a thin layer on aluminum.
To understand this, let's break down the answer choices:
1. All aluminum products are treated with a plastic coating: This is not entirely true. While some aluminum products may indeed have a protective coating, it is not the primary reason for the corrosion durability of aluminum. Additionally, not all aluminum products are coated with plastic.
2. Aluminum does not undergo oxidation: This statement is incorrect. Like most metals, aluminum does undergo oxidation. However, the key difference lies in how aluminum reacts with oxygen.
3. Very unreactive aluminum oxide forms a thin layer on aluminum: This is the correct answer. When aluminum reacts with oxygen, it forms aluminum oxide (Al2O3). The resulting aluminum oxide layer adheres tightly to the surface of the aluminum, acting as a protective barrier. This layer serves as a physical barrier that prevents further oxygen and water from reaching the underlying aluminum, thus inhibiting corrosion.
4. Aluminum does not react with oxygen: This statement is incorrect. Aluminum does react with oxygen, as previously mentioned, to form aluminum oxide.
Therefore, the correct answer is option 3: very unreactive aluminum oxide forms a thin layer on aluminum.
The reason for the corrosion durability of aluminum is:
3. very unreactive aluminum oxide forms a thin layer on aluminum.
Aluminum has a high reactivity with oxygen, but when exposed to oxygen in the air, it quickly forms a layer of aluminum oxide on its surface. This aluminum oxide layer acts as a protective barrier, preventing further corrosion of the underlying aluminum. It is a very thin layer that is tightly adherent to the metal surface, making it highly resistant to corrosion. This natural oxide layer is self-healing, meaning that if the surface is scratched or damaged, it quickly reforms, protecting the aluminum from further corrosion. This property of aluminum oxide makes it suitable for various applications where iron would corrode.