### Theory:

During the rainy season, what happens to the metal benches and tables? Do they turn reddish-brown in colour? Yes.
The usage of iron and steel articles have become an integral part of our day life. For instance, iron is used in making bridges, ships, cars, truck bodies, grills in windows and many other articles.

Chemical reactions on the surface of shining metals and other items causes these articles to lose their glow. When exposed to atmospheric air, silver articles turn black.
Rusted iron chain
An iron turns into rust when exposed to air and moisture in the atmosphere.
Rusting is an example of  a chemical change where the process cannot be reversed, and a new substance is formed. This is also called as a chemical reaction.

$\begin{array}{l}\mathit{Iron}+\mathit{Oxygen}+\mathit{Water}\to \mathit{Iron}\phantom{\rule{0.147em}{0ex}}\mathit{oxide}\left(\mathit{rust}\right)\\ \mathit{Fe}+{O}_{2}+{H}_{2}O\to {\mathit{Fe}}_{2}{O}_{3}\end{array}$

Rusting of iron
Note: Rusting becomes faster when it is humid (i.e. high moisture content present in the atmosphere) and high salt content in water.
Example:
Similarly, when exposed to air for an extended period of time, brass vessels that contain copper as one of their constituents produce a greenish coating.

This is caused by a chemical reaction between copper and moist air, which results in the formation of copper carbonate and copper hydroxide.
Fact: The Iron Pillar at the Qutub complex in Delhi is more than $$1600$$ years old. This pillar has not rusted still now, which is a testament to the advances in metal making technology in the $$16$$th century in India.