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Rust Definition
Rust is iron oxide, a reddish-brown oxide formed as a result of a reaction between iron and oxygen in the presence of water or moisture.
- The chemical composition of rust is composed of Fe2O3.nH2O and (FeO(OH).Fe(OH)3. Rust is often associated with corrosion of iron, even though both of them are quite different in their process.
- Rusting is a chemical process that can occur in all masses of iron, where the presence of water and oxygen can cause even large masses of iron to rust.
- The term rusting is often used exclusively for the corrosion of iron and its alloys like steel.
- Rust can either occur on the surface of the metal or within the metal. The surface rust is usually flaky and friable that provides no protection to the underlying iron.
- There are different structures of rusts that are distinguishable by techniques like spectroscopy or visual observation.
- Rusting is often taken as a negative mechanism, but some form of rusting can increase the stability of the metal by forming a thin coating over the iron below. This form of rust is called stable rust.
- Rust is an oxidation process caused by oxygen and other oxidizing agents; however, it is not the only process. The oxidation products combine with other molecules to form rust.
- The primary catalyst for the process of rusting is water. Tiny water molecules can penetrate through the microscopic pits on the iron or steel structures.
- Besides being an oxidation process, rusting is also an electrochemical process resulting from the transfer of electrons from iron to oxygen.
- Intense rust on iron and steel products is a problem as such metals products are used for different purposes.
- Rust prevention can be achieved by the addition of coatings on the surface. These coatings usually protect the layer lying underneath from coming in contact with air and moisture.
![Rust vs Corrosion](https://scienceinfo.com/wp-content/uploads/2021/09/Rust-vs-Corrosion.jpeg)
Corrosion Definition
Corrosion is the process of conversion of metal into a more chemically stable form like oxides, hydroxides, and sulfides.
- It is a natural process that involves the gradual destruction of materials (which is usually metal) by chemical as well as electrochemical means.
- Corrosion is often used synonymously with rusting; however, rusting is almost exclusively used in the case of iron and its alloys whereas, corrosion can occur in different types of metals.
- Corrosion can also be called electrochemical oxidation, as the reaction occurs in the presence of an oxidant and involves the transfer of electrons from one chemical species to another.
- Corrosion can also occur in materials other than metals like ceramics and polymers, which is often described as degradation.
- Corrosion is a destructive process that deteriorates the useful properties of materials like strength, appearance, and permeability.
- Corrosion doesn’t necessarily occur due to exposure to moisture or air and might require stronger factors. It is, however, a diffusion-driven process that occurs primarily on exposed surfaces.
- The overall chemical process of corrosion is quite complicated. The process begins at a spot where oxidation causes the spot to behave as an anode.
- The electrons from the spot then move through the surface and reach a new spot. The electrons then take up the oxygen present in the area to form water molecules. This new spot behaves as a cathode.
- Corrosion, like rust, can result in the loss of different properties of the compound, and thus, it is useful to apply procedures to prevent it.
- The corrosion resistance of different substances can be increased by processes like surface treatments and cathodic or anodic protection.
6 Key Differences (Rust vs Corrosion)
Characteristics | Rust | Corrosion |
Definition | Rust is iron oxide, a reddish-brown oxide formed as a result of the reaction between iron and oxygen in the presence of water or moisture. | Corrosion is the process of conversion of metal into a more chemically stable form like oxides, hydroxides, and sulfides. |
Surfaces | Rust primarily occurs on the surface made up of iron and its alloys. | Corrosion can occur on different surfaces like skin, metals, wood, etc. |
Caused by | Rust is caused by exposure to air or moisture. | Corrosion is caused as a result of exposure to air, moisture as well as other chemicals like acids and bases. |
Observed as | Rust is observed in the form of a red or orange coating on the surface of the substance. | Corrosion can be observed on different surfaces in different forms. |
Chemistry | Rust is composed of iron oxides together with other similar compounds. | Corrosion can be composed of salts of different elements. |
Biological role | No biological process is involved in rusting. | Microbial corrosion can occur in the presence of some specific microorganisms. |
References
- Gautum SD, Pant M and Adhikari NR (2016). Comprehensive Chemistry, Part 2. Sixth Edition. Heritage Publishers and Distributors Pvt. Ltd.
- https://pediaa.com/difference-between-corrosion-and-rusting/