Methods of Preventing Corrosion
Corrosion is a chemical reaction that occurs when metal is exposed to certain environmental stress. Rust is one of the most common forms of corrosion. When metals corrode, they become weakened, which can be dangerous in metal beams that support a structure or in tin roofing. Many metals undergo special treatments to prevent or slow down the reaction of corrosion.
Covering With Other Metals
Coating or plating a highly reactive metal that is easily corroded, like iron, with a metal that corrodes faster than the interior metal, like zinc, is one common way of increasing corrosion resistance, says Sweet Briar College. By covering the original metal in a coating of a highly reactive material, the coating creates a solid layer of corroded material that prevents further damage. Some metal coatings, such as magnesium or tin, are less reactive and corrode slower, making them appropriate for protective coatings as well.
Other metals are not the only materials useful for creating corrosive resistant coatings on iron and steel. Enamel, polymer or plastic, and epoxy coatings, can all be utilized in different applications, according to the Kansas Department of Transportation. These coatings work by preventing the oxygen and other components necessary for the corrosion process from reaching the surface of the metal. Enamel works well, but, if it becomes chipped or cracked, corrosion can take place underneath the coating. More flexible and damage-resistant materials, like polymer and epoxy-based formulas last longer and provide more corrosion protection. Even a thin layer of oil can prevent basic corrosion, which is the reason small metal items like guns are regularly coated with the substance.
Many forms of corrosion, including the process of rusting, require some amount of moisture. Removing the moisture around a piece of metal can slow or prevent corrosion, says the Die Deutschen Versicherer website. Desiccants are compounds that absorb water from the air around them, but they must be used in sealed packages or they will simply fill up with moisture and become ineffective. Silica gel and aluminum silicate are two common desiccants and can commonly be found in food packages that would become degraded by excess moisture. When enough desiccant packets are added to a closed container of metal items, they can prevent corrosion for a short amount of time.
Folds and crevices in pressed metal sheets, such as those used to create the body of most cars and trucks, are often more prone to corrosion, says Wichita State University. Dirt, sand and other debris is also easily trapped in these crevices, increasing the damage from corrosion. These minute openings are often found where sheets of metal are connected or where the edges of metal meet other materials like glass or rubber. Careful applications of protective coatings often work for these problem areas, but the best method for reducing crevice corrosion damage is to design objects with as few crevices as possible.
- Sweet Briar College: Factors Affecting Corrosion
- Kansas Department of Transportation: EVALUATION OF CORROSION PROTECTION METHODS FOR REINFORCED CONCRETE HIGHWAY STRUCTURES
- Die Deutschen Versicherer: Classification of corrosion protection methods
- Wichita State University: Crevice Corrosion Theory, Mechanisms and Prevention Methods