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Scientifically speaking rust is called oxidation, which occurs when oxygen comes in long-term contact with certain metals, most commonly iron. Over time, the oxygen combines with the metal at an atomic level, forming a new compound called an oxide and weakening the bonds of the metal itself. If the base metal is iron or steel, the resulting rust is properly called iron oxide. Rusted aluminum would be called aluminum oxide, copper forms copper oxide and so on.
As rust has higher volume than the originating mass of iron, its buildup may force apart adjacent parts - a phenomenon known as rust smacking.The rusting of iron is one of the more widely used examples of corrosion. This electrochemical process requires the presence of water, oxygen and an electrolyte and leads to the formation of hydrated iron oxides.
Formation Of Rust
Rust, which is technically known as oxidation, is the process that results when there is an interaction between oxygen and various metals for an extended time period. The oxygen and metal combine at an atomic level creating a new compound termed an oxide, and the metal bonds are weakened. When iron or steel are the base metal, then the rust formed is called iron oxide (and similarly rusted aluminum is called aluminum oxide).
Iron and steel are apparently hard in appearance, but the minute ruptures and pits in the exposed metal facilitate the penetration of water molecules, and rust is formed. Rusting is an electrochemical process that is commenced with the move of electrons from iron to oxygen, and the process is expedited in salt water. With the passage of time, and availability of water and oxygen, an iron body will be converted into rust and be disintegrated.
Damage Due To Rust
Rust is a serious issue, and unless taken seriously in the initial stages,may be uncontrollable and cause extensive damage by the deterioration, failure, or weakening of components or appliances. Rust is extremely harmful for cars. As the body is stained, the rust spreads to other parts of the car body if exposed to extreme moisture in the weather- and if appropriate rust prevention measures are not taken. Electrical appliances and instruments may fail if the metallic parts are rusted since rust is a non-conductor of electricity.
Similarly, the machines and equipment that use magnets may malfunction due to the inferior magnetic properties of rust. Furthermore, since the rust formation increases the volume of the initial iron mass, adjacent rusted parts may be forced apart, causing failure of the machines or assemblies. Rusting of iron in reinforced concrete bridges may be a source of serious structural problems that may be extremely dangerous, and also require huge expenditures for repairs.
Rust Prevention
#Galvanization
Galvanization is an important metallurgical process for rust prevention that involves the application of a zinc layer, by electroplating or hot dip galvanizing, on the iron or steel object desired to be protected. In this process, iron or steel is dipped in melted zinc at a temperature at which there is a great similarity between these materials, and an alloy is formed, with a zinc coating at the exterior surface. The coating of zinc protects the metal part object from oxidation and environmental effects like extreme temperatures, snow, wind, and rain.
Zinc is used since its corrosion resistance characteristics are better than iron and steel, due to which it forms a physical obstruction against corrosion, and also shields the exposed steel if the zinc layer is damaged. Galvanization is not successful at joints and holes because the zinc coating is penetrated by corrosion and other processes may be used for such applications. However, galvanization is preferred to be used for the protection of iron and steel being economical, simple in use, and long lasting.
#Cathodic protection
Cathodic protection is a technique used to inhibit corrosion on buried or immersed structures by supplying an electrical charge that suppresses the electro-chemical reaction. If correctly applied, corrosion can be stopped completely. In its simplest form it is achieved by attaching a sacrificial anode thus making the iron or steel the cathode in the cell formed. The sacrificial anode must be made from something with a more negative electrode potential than the iron or steel, commonly zinc, aluminium or magnesium.
#Painting
Rust formation can be controlled with coatings, such as paint, that isolate the iron from the environment. Large structures with enclosed box sections, such as ships and modern automobiles, often have a wax-based product (technically a "slushing oil") injected into these sections. Such treatments also contain rust inhibitors. Covering steel with concrete provides protection to steel by the high pH environment at the steel-concrete interface.
