Question

Why Aluminium metal gradually corrodes when it comes in reaction with air?? plz. ans. fast

Answer 1

aluminium forms a layer of Al2 O3 when it comes in contact with air . this layer protect it from further oxidation.

Answer 2

Aluminum is chemically very reactive
used as rocket propellant for propulsion of the space shuttle's solid fuel rockets. Additionally, the reaction of aluminum with water releases a tremendous amount of energy:

AI + 3H2O → AI(OH)3 + 3H2 ↑

Corrosion is the reaction of aluminum with water and the subsequent deterioration of its properties. Corrosion, by definition, is a slow process, requiring days or years to occur to a noticeable extent, as opposed to similar electrochemical reactions such as etching, brightening, or anodizing which occur in minutes or less.

Aluminum alloys may corrode via several different pathways.

1.atmospheric corrosion.

2.Uniform corrosion_
 In acidic (low pH) or alkaline (high pH) solutions, the aluminum oxide is unstable and thus non-protective.

3.Galvaniv corrosion_
Galvanic corrosion, also known as dissimilar metal corrosion, occurs when aluminum is electrically connected to a more noble metal, and both are in contact with the same electrolyte

4.Crevice corrosion

Crevice corrosion can occur in a saltwater environment if the crevice becomes deaerated, and the oxygen reduction reaction occurs outside of the crevice mouth. Under these conditions, the crevice becomes more acidic, and corrosion occurs at an increasing rate.

so on......