What is corrosion?

What is corrosion?

Corrosion is the deterioration of metals and some materials by chemical or electrochemical reactions when exposed to environmental factors. This process is most commonly seen in metals, but other materials can also be affected by corrosion. One of the main causes of corrosion is the reaction of metals with oxygen or water in the atmosphere. This reaction causes the formation of metal oxides or hydroxides on the surface of the metal. The oxidation of metal is one of the most common forms of the corrosion process, and this means that the metal is slowly worn away and its structural properties are weakened. As a result, corrosion can negatively affect the material's strength, appearance, and functionality.

How does corrosion occur?

Corrosion is a deterioration process that occurs as a result of the interaction of metals with environmental factors, especially oxygen and water. This interaction is often electrochemical in nature and can lead to changes such as wear, dissolution, or oxidation on the metal surface.

The basic mechanism of electrochemical corrosion is based on the ionization and separation of atoms from the metal surface. In this process, anodic (oxidizing) and cathodic (reducing) regions form on the metal surface. In anodic regions, the metal turns into metal ions by releasing electrons. These released electrons are transported to the cathodic regions and react there in various ways. For example, in the presence of water and oxygen, these electrons can react with oxygen to form hydroxyl ions.

These anodic and cathodic reactions create an electrical circuit on the metal surface, causing corrosion to progress. As a result of electrochemical reactions, metal oxides, hydroxides, or other salts can form on the metal surface. These compounds are often known as corrosion products and degrade the original properties of the metal.

The corrosion process can vary depending on the type of metal, environmental conditions, and defects on the metal surface. For example, some metals tend to self-protect by forming passive oxide layers, but if these layers are damaged, corrosion can progress rapidly.

What are the types of corrosion?

Corrosion is a general term that describes the deterioration processes that occur in metals or alloys when they are exposed to various agents and environments. There are many types of corrosion, and this variety is determined by the mechanism of corrosion formation, the surface it affects, or the characteristics of the environment. Here are some common types of corrosion and definitions of these types:

1. Galvanic corrosion: This occurs when two different metals or alloys come into direct or indirect contact with each other in a conductive electrolyte. In this type of corrosion, one metal becomes more active than the other due to the potential difference between the two metals and corrodes.

1. Pitting corrosion: This is a localized corrosion type that occurs at specific points or small regions on the metal surface. Very small and often invisible pits or holes form in the metal.

1. Surface corrosion: This type of corrosion can affect a large area or the entire surface of the metal. Smooth and generally uniform wear is observed on the affected surface.

1. Erosion corrosion: This type of corrosion occurs when a metal surface rubs against a moving fluid (such as water or air). The friction effect of the fluid causes an abrasive effect on the metal surface and can lead to accelerated corrosion.

In addition to these four main types of corrosion, there are other types of corrosion that can occur in various environments and conditions. These types can vary depending on the specific conditions to which the metals are exposed or the substances they interact with.

What is corrosion resistance?

Corrosion resistance is a measure of a material's ability to resist corrosion. Corrosion resistance of materials can be improved by using corrosion-resistant coatings or alloys.

Why does corrosion occur?

Corrosion is the deterioration of metals and other materials that occurs as a result of their interaction with environmental factors. This deterioration is caused by a combination of factors. The main causes of corrosion are as follows:

• Atmospheric conditions: Moisture, oxygen, and pollution can cause metals to oxidize. Coastal areas with salty air, in particular, increase the risk of corrosion for metals.

• Chemical substances: Acidic or basic substances can react with metals. In industrial areas, contact with such substances can accelerate corrosion.

• Electrochemical reactions: The combination of different metals can accelerate corrosion due to the potential difference. This is known as galvanic corrosion.

• High temperatures: High temperatures can accelerate corrosion by increasing the rate of chemical reactions. This can be a problem, in particular, in hot water systems or machines operating at high temperatures.

• Biological effects: Some microorganisms have metabolic processes that can accelerate corrosion on metals. This type of corrosion is called microbiological corrosion.

• Mechanical effects: The rapid movement of fluids or the presence of abrasive particles can cause abrasive effects on the surface of metals.

All of these factors are the fundamental factors that affect the formation and progression of corrosion. Different metals may have different sensitivities to these factors, and therefore the right material selection is an important step in preventing corrosion.

What are the methods of corrosion protection?

There are several methods of corrosion protection, including:

• Corrosion-resistant coatings: These coatings provide a barrier between the metal and the environment, preventing corrosion from occurring.

• Cathodic protection: This method uses an electric current to create a protective layer on the surface of the metal.

• Corrosion-resistant sprays: These sprays provide a temporary protective coating for metals.

• Passivation: This process creates a protective oxide layer on the surface of the metal.

What are the hazards of corrosion?

Corrosion is a process that causes the deterioration of metals and some other materials. The effects of corrosion can be not only aesthetic but also cause significant structural and economic damage. Some of the hazards of corrosion include:

• Degradation of mechanical properties: Corrosion can adversely affect the mechanical properties of metals, especially their strength and hardness. This can lead to the material failing earlier than expected.
• Structural damage: Corrosion can cause structural damage to metals, such as thinning, hole formation, or the progression of cracks. This can pose a major safety risk for bridges, buildings, and other structures.

• Economic losses: Corrosion can lead to costly repairs, modifications, and early replacement requirements. This can increase operational costs and reduce return on investment.

• Functional losses: Corrosion can lead to equipment or component failure earlier than expected, which can lead to business interruptions and production losses.

• Aesthetic losses: Corrosion can cause staining, discoloration, or the formation of unsightly corrosion products on metal surfaces, which reduces their aesthetic value.

• Energy loss: Corrosion can cause efficiency losses in energy systems that are critical for heat and electricity transmission. For example, corrosion that occurs on the inner surface of a pipe can make it more difficult for the fluid to flow through that pipe, which can increase pumping costs.

• Environmental problems: Corrosion products can sometimes be toxic and can leach into waterways or soil. This can lead to environmental contamination and disruption of the ecological balance.

These hazards demonstrate that corrosion can be a serious problem not only for the integrity of materials, but also from an economic and environmental perspective. Therefore, corrosion prevention and control is of critical importance for many industries.

How to Clean Corrosion?

Corrosion cleaning is performed using different methods depending on the type of material affected, the severity of the corrosion, and the specific application requirements. Common methods used to clean corrosion include:

• Mechanical Cleaning:

• Sanding: The corroded surface is cleaned by sanding it with sandpaper or discs of various grit sizes.
• Brushing: The corroded surface is brushed using metallic brushes. This is suitable for light corrosion surfaces.
• Sandblasting: This is a method of cleaning corrosion by spraying sand or other abrasive materials onto the surface at high pressure. This method is effective for cleaning large surfaces and deep corrosion.

• Chemical Cleaning:

• Acid Cleaning: Weak acids (such as citric acid or phosphoric acid) are used to dissolve corrosion products. This method allows the corrosion to be cleaned without damaging the metal itself.
• Corrosion Removers: Commercially available corrosion removers are formulated for specific metal types and can effectively clean corrosion products.

• Electrochemical Cleaning:

Corrosioned metal is cleaned by an electrochemical process using the corroded metal as an anode or cathode in an electrolytic solution. This method uses an electric current to remove the corrosion products from the metal surface.

• Laser Cleaning:

High-energy laser beams are used to clean corroded surfaces. The laser energy vaporizes the corrosion products, separating them from the surface.

When choosing a corrosion cleaning method, the type of material to be cleaned, the depth of the corrosion, the available equipment, and environmental impacts should be considered. Additionally, it is generally recommended to protect the surface with a protective coating or treatment after corrosion cleaning. This helps to prevent corrosion from recurring.