Question

Corrosion rate of aluminum is _________ when compared with corrosion of mild steel in open oxygenated atmosphere.

(a) small

(b) medium

(c) large

(d) very small

This question was addressed to me during an online interview.

Origin of the question is Corrosion Rate Expression topic in portion Corrosion Principles of Corrosion Engineering

Answer 1

The correct answer is:

(d) very small

Explanation:

Aluminum generally has a very small corrosion rate when compared to mild steel in an open oxygenated atmosphere. This is because aluminum forms a stable, protective oxide layer (Al₂O₃) on its surface when exposed to air. This oxide layer is highly resistant to further corrosion, which significantly reduces the corrosion rate of aluminum in oxygenated environments.

On the other hand, mild steel does not form a protective oxide layer as effectively, leading to faster corrosion, especially when exposed to moisture and oxygen.

Thus, the corrosion rate of aluminum is very small in comparison to mild steel under similar conditions.