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What is corrosion?

Causes, types, and how to prevent corrosion

Corrosion can affect various materials, causing deterioration and damage. If left untreated, corrosion can be visually unappealing at best or an expensive safety hazard at worst. We define corrosion, its causes and types, as well as preventative measures to help you better understand and combat the steel deterioration process.

Rusty steel

Corrosion definition

Corrosion is the gradual deterioration of materials, caused by chemical reactions with the environment. It is a natural process and is most associated with metals, but it can also affect other materials like ceramics and plastics. The corrosion process happens when a material reacts with substances such as oxygen, water, acids, or salts, leading to the breakdown of its structure.

Causes of corrosion

Several factors contribute to corrosion, mainly occurring when metal is exposed to external variables. The primary factors include:


When metals collect moisture, an electrochemical reaction causes the steel to corrode. The corrosion process is often accelerated by dissolved salts or impurities in the water.


Oxygen reacts with metal atoms, forming metal oxides – otherwise known as rust. Rust is just one type of corrosion, but it’s one of the biggest types to affect steel.

Unless the steel is kept in an oxygen-free environment, it will slowly rust over time, even if you take good care of it. Both oxygen and moisture are required for steel to rust.


Acidic substances can corrode metals by attacking their surface. Industrial processes, pollution, and even natural sources like acid rain can introduce acids to the environment, increasing the risk of corrosion. Industrial companies, or those that work in construction or similar sectors, are at a higher risk.

Rusty steel

Types of corrosion

There are many forms of corrosion, each with distinct characteristics and causes. The most common types include:

Uniform corrosion

This type of corrosion occurs evenly across the surface of the material, resulting in a gradual loss of material thickness. Uniform corrosion is typically caused when metal is exposed to moisture or atmospheric conditions.

Pitting corrosion

Pitting corrosion is when holes form in the metal surface. It often starts with a small scratch, which then becomes an active site for corrosion. Pitting corrosion can be particularly destructive, leading to rapid damage.

Galvanic corrosion

Galvanic corrosion occurs when two different metals come into contact in the presence of an electrolyte, such as moisture. The metal that is less resistant to corroding corrodes quicker due to the electrochemical potential difference between the two metals.

Uniform corrosion is the most common type of corrosion; fortunately, it is also among the easiest types to prevent.

Preventing corrosion

Metal corrodes very quickly without a protective coating. Preventive measures can help minimise the risk and impact of corrosion. Some effective strategies include:


Hot dip galvanizing involves dipping steel into a bath of molten zinc, causing a chemical reaction where the zinc metallurgically bonds with the steel. As the zinc and steel atoms bond, it makes the steel very durable and corrosion-resistant. Galvanizing is among the most effective ways to protect steel against corrosion.

Top-layer coatings

Applying a surface coating such as powder coating or paint can protect steel against corrosion. Top-layer coatings can also be used after the steel has been galvanized to enhance the steel’s longevity.

Combining hot dip galvanizing and powder coating on the same steel structure is known as a duplex coating. You can learn about the benefits of duplex coatings here.

Environmental changes

Changing your environment can reduce the rate of corrosion. However, this may not always be possible, especially if the steel is outside or near corrosive chemicals.

Rusty steel

How to remove rust from metal

There is still hope if your steel has started to corrode. A surface-cleaning technique such as shot blasting can remove any existing rust off the steel. While shot blasting on its own won’t prevent rust from building up again, it is a crucial step before galvanizing to make the process more effective.

If your steel is very rusty, it may not be possible to recover. In the future, book in with a reputable galvanizing company as soon as possible after steel fabrication.

By understanding the causes and types of corrosion, as well as implementing preventive measures, it is possible to minimise its impact.

Joseph Ash Galvanizing can remove rust from your steel and increase your steel’s resistance against corrosion. Find your nearest site and get a quote today.

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