Aluminium is more reactive than iron but aluminium is less easily corroded than iron, because

Aluminium is higher than iron in the reactivity series, making it more chemically reactive [c5]. However, aluminium is less susceptible to corrosion because it naturally develops a thin, tough oxide layer (Al2O3) when exposed to air [c2]. This layer acts as a protective barrier, preventing further oxygen and moisture from reaching the underlying metal [t2][t6]. In contrast, the oxide layer formed on iron (rust) is porous and flaky, allowing air and water to penetrate and continue the corrosion process [t4]. This phenomenon of forming a protective film is known as passivation [t2]. While iron can be protected through processes like galvanisation or anodising to mimic this effect, aluminium inherently possesses this resistance due to the immediate formation of its oxide coat [c2][c4]. Therefore, despite its high reactivity, the protective oxide layer ensures aluminium's durability in atmospheric conditions [t8].

Sources

1. [1] Science , class X (NCERT 2025 ed.) > Chapter 3: Metals and Non-metals > 3.2.5 The Reactivity Series > p. 45
2. [2] Science , class X (NCERT 2025 ed.) > Chapter 3: Metals and Non-metals > p. 42
3. [3] Science , class X (NCERT 2025 ed.) > Chapter 3: Metals and Non-metals > 3.5.1 Prevention of Corrosion > p. 54