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In this article, we will discuss corrosion, its types and causes.

What is Corrosion?

It is defined as a natural process that causes that transition of pure metal undesirable substances when reacting with substances such as water or air. This reaction causes damage and destruction of the metal, starting with the portion of the metal exposed to the atmosphere and spreading to the bulk of entire metals.

Corrosion is a phase where the metal is corroded. Corrosion is a natural process, and chemically active metals get corroded in the presence of a moist atmosphere.

Corrosion Causes

There are various causes of corrosion. Some of them are as follows:

  1. The presence of impurities like salt.
  2. Metal exposure to moisture, specifically salts water.
  3. If the temperature is increased, the corrosion also increases.
  4. Metal exposure to air containing gases such as SO2, SO3, and CO2
  5. Acids may accelerate the corrosion process.

Types of Corrosion

There are various types of corrosion. Some of them are as follows:

Pitting Corrosion

Pitting corrosion is very volatile and difficult to detect. It occurs at the focal point and continues to create a corrosion cell surrounded by a normal metal surface. After this, "Pit" has been created that can take different shapes. The pit initially penetrates metal from the surface in a vertical direction and ultimately leading to structural failure.

Uniform Corrosion

It is the most common type of corrosion that usually occurs evenly over wide material surface areas.

Stress Corrosion

Stress corrosion cracking leads to the expansion of cracks due to a corrosive environment, especially at high temperatures, and can lead to the failure of ductile metals under tensile stress. Among alloys, this form of corrosion is more prevalent than metal alloys. It depends on the particular chemical environment in which only small concentrations of active chemicals are needed for catastrophic cracking.

Galvanic Corrosion

It is the most popular and important type of corrosion that occurs when two different metals interact in the presence of electrolytes. The active metal (anode) corrodes, and the noble metal (cathode) is shielded by the galvanic cell. There are various factors that influence galvanic corrosion like metals type, environment, and relative anode size.

Intergranular Corrosion

This corrosion occurs due to the presence of impurities in the grain borders that separate the grain produced during the solidification of the metal alloy. It can also occur through the degradation or enrichment of an alloy at the grain boundary.

Erosion Corrosion

Erosion corrosion is caused due to mechanical abrasion between metal surfaces and corrosive fluids. In this situation, the metal surface is gradually eroded by the abrasion of quick-moving fluids, and cavities also are created. This type of corrosion is frequently seen in metal tubes that hold moving fluids.

Prevention of Corrosion

To avoid huge losses of metal, it is important to prevent corrosion. Most of the structures that we use are made of metal. It involves bridges, vehicles, machinery, household items such as doors, railway lines, window grills, and many more.

There are various steps to prevent corrosion. Some of them are as follows:

  • Ensure that the surface of the metal should be dry and clean.
  • Put a backfill layer, such as limestone, with underground piping.
  • Use drying agents.
  • Using non-corrosive metals such as aluminum or stainless steel.
  • Use a barrier product and coatings like oil, carbon fiber coating, grease, and oil.

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