Certain metallic objects develop alterations on their surface when they are left stagnant or untouched for a considerable period of time. This is referred to as corrosion and causes metals to gradually degrade. Rusting is a type of corrosion in metals. Rust develops from metal oxidation along with water absorption; these create Fe2O3 bound to water molecules. This happens to metals and their alloys. Subsequently, metallic objects react with oxygen in the atmosphere and can become rusted in a humid environment. Rust is an iron oxide and it can happen slowly or quickly, depending on various factors.
The time it takes for metal to rust depends primarily on its air and water contact. Under salt water, metal rusts faster than in freshwater.
Here are some instances
of how causative factors of rusting determine the time it takes for metals to rust:
- Due to their additives, certain kinds of metals rust more slowly, such as nickel and chromium in stainless steel, which binds to the metal atoms and prevents them from oxidizing; zinc is present in galvanised steel and an aluminium-silicon alloy is found in aluminium steel.
- Painting or coating metal with oil will prevent contact between oxygen and water.
- The atmosphere can be devoid of humidity, and it doesn’t rain much in some areas. For example, vehicles survive out in the desert longer because it’s so dry and rusting slows down.
- Hot metal tends to rust faster than cold metal – heat generally accelerates chemical processes. This is why car exhaust headers and manifolds rust quickly (unless coated or made of materials that do not rust).
- Thin metal can rust more quickly than thick metal (holes might appear). The rate of rusting may be the same, but thin metals will develop more holes in them compared to thicker metals. Although other steel wools are made of stainless steel and are coated, some types of steel wool also rust quickly (they are usually exposed to water, which does not help).
- The electrical condition can affect the rate of rusting in water. Regarding electrical contact, if you have two different types of metal and both are in contact with salt water, a battery will be created. Current spreads and energy are produced by metal corrosion. Many companies sell zinc blocks that can be attached to boats to corrode the zinc first so other metals are protected.
Here are some guidelines to help answer this question:
- The larger the exposed surface area, the sooner it becomes rusty (metal powder rusts much more easily than solid steel
- Metal alloys, including steel, resist rusting more than plain metal
- Metal surface coating or other processes can be used to avoid rusting
- Exposure to a combination of salt and water will greatly increase the rate of rusting
- The higher the temperature, the higher the chances of rusting
Information that is necessary for determining the time it takes for metals to rust:
- Weight loss (the reduction in the weight of the metal during the reference time period)
- Density (the density of the metal)
- Area (the total initial surface area of the piece of metal)
It is impossible to predict how long a metal will take to rust without understanding each of the above-mentioned factors.
By storing devices made from metal with oil or acrylic paints in cool, dry containers and by painting exposed metal surfaces, rust is preventable. With the application of protective coatings, the risk of rusting can be reduced. It is also recommended that metal should be cleaned regularly because dirt absorbs humidity.
Here, at Romco, we deal with the recycling of rusted metals to reduce global dependence on landfill sites through recycling and smart waste management.