In Quran 18:96, there is a description of a figure known as Thu-Al-Karnain who, when constructing a barrier with iron, orders for tar to be poured over it:

This verse describes the use of tar to coat iron. While the context of the Quranic story involves constructing a barrier, the mention of tar is particularly significant from a scientific perspective. Today, we know that rust, a red oxide formed by the reaction between iron, oxygen, and water, can be prevented by isolating the iron from these elements.

Rust is a product of the chemical reaction between iron and oxygen, which occurs when moisture is present. The process, known as oxidation, results in the formation of iron oxide, which weakens the material over time. Rust can be prevented by blocking the iron from exposure to water and oxygen, which is why coatings like paint, lacquer, or tar are commonly used in modern times to protect iron and steel from corrosion.

To prevent rust, it is essential to isolate the iron from moisture and air. Coating the metal with materials such as paint or tar is an effective method to achieve this. Tar, a substance that can form a protective barrier, prevents water and oxygen from reaching the iron, thus stopping the rusting process.

The process of rust formation and how to prevent it was unknown to humanity until relatively modern times. The concept of coating iron with substances like tar to prevent rust was not discovered until after the advent of industrialization. However, this was described accurately in the Quran more than 1400 years ago in the story of Thu-Al-Karnain, where tar is used to coat iron, a method consistent with what we know today for preventing rust.