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Rust Prevention by Oil Undercoating

Rust formation on metal surfaces is a result of corrosion. If the metal forms an important part of a structure, its weakening can eventually cause a structural collapse. This is what happened to Silver Bridge in West Virginia in 1967, where 46 people died. Another incident with a similar nature occurred in Greenwich Connecticut in 1983 when the Manus Bridge collapsed, killing three people.

  1. Rust Formation

    • Rust formation proceeds through what is called an electrochemical process because of electron transfer, which in this case is from the iron to the oxygen. The iron is the anode (a metal element that readily donates an electron) while the oxygen is called the cathode (a metal element that readily accepts an electron). The movement of the electrons proceeds via a medium called electrolyte which, in this case, is a weak acid such as water.

      Basically, rust forms under the presence of three elements - iron (Fe), oxygen (02) and water (H20). The presence of air moisture brings in carbon dioxide which reacts with the water to form a better electrolyte called the carbonic acid, another weak acid. As oxygen, water and air moisture are readily available in the environment, they easily react with the iron metal to form rust. The reaction is called the oxidation process because the iron gains oxygen to form iron oxide (the reddish or orange thing called rust).

      The natural abundance of the elements oxygen, water and air moisture make rust formation easy to occur. For this reason, frequent exposure to water and air eventually weakens the steel (the iron source) and leads to its eventual damage. Although it cannot be completely prevented, you can slow down the process by minimizing the contact between the three elements. Without any of these elements, corrosion is impossible. In the industry of metals, prolonging the metal’s functionality is achieved through the application of oil undercoating.

    Oil Coating for Rust Prevention

    • Observe how oil reacts with water. Water’s polarity has the five-carbon limit, which means that the only compounds capable of being dissolved in water should have five or less Carbons in its structure. Oil, on the other hand, is a non-polar compound consisting of a long chain of Hydrocarbons (Carbons and Hydrogen), making it insoluble in water. Thus, oil coating helps repel water and prevent rust formation.

    Best Oil Undercoating

    • Manufacturers would often incorporate a compound in the oil that acts as rust inhibitors. The better oil performs well in the humidity cabinet test, where the oil is exposed to 120°F. The longer time it takes for the rust to form, the better the oil is. It is always best to apply the oil after removing any rust that has formed already on the metal. If not, the adhesive properties of your paint will be minimized.

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