How Long Does Galvanized Steel Last？

The lifespan of galvanized steel depends on factors such as the environment, coating thickness, and maintenance. In mild, non-industrial settings, galvanized steel can last up to 70 years. However, in harsh, corrosive environments—such as coastal areas exposed to salt water or industrial zones with sulfur dioxide in the air—the lifespan can be significantly reduced to just 5–10 years. 

This article will explore the expected lifespan of galvanized steel in different environments, explain the key factors that influence its durability, and provide tips on how to extend its service life.

The Lifespan Of Galvanized Steel

The lifespan of galvanized steel is largely influenced by environmental conditions, including the degree of industrial pollution, salt exposure, and humidity. An increase in corrosive elements in the environment will shorten the service life of galvanized steel.

The corrosion classification system defined by the ISO 9223 standard helps predict corrosion rates and the durability of galvanized steel. The categories range from C1 (very low corrosivity) への C5 (very high corrosivity), reflecting the levels of pollutants, moisture, and salt in the atmosphere.

The table below illustrates the differences in the lifespan of galvanized steel under various environmental conditions.

Environmental Factors Prevent Galvanized Steel From Lasting

The following are the environmental elements that affect the durability of galvanized steel. When combined, they create aggressive conditions that rapidly degrade the zinc coating, leading to faster corrosion of the underlying steel.

Salt Exposure

In coastal areas or regions where roads are salted in winter, salt particles settle on the steel surface. When combined with moisture, they form a conductive solution that accelerates the deterioration of the zinc coating. Once the zinc is damaged, the underlying steel corrodes, shortening its lifespan.

Galvanized steel can still be used in environments with moderate salt exposure, such as in coastal buildings or fences. However, in high-salt environments, such as areas with heavy maritime exposure or structures in direct contact with seawater, galvanized steel is less suitable.

Industrial and Atmospheric Pollutants

Industrial and environmental contaminants, such as sulfur dioxide (SO₂) and nitrogen oxides (NOₓ), accelerate the corrosion of galvanized steel. These pollutants combine with moisture in the atmosphere to produce acids, such as sulfuric and nitric acid, which degrade the zinc layer. 

In urban and industrial zones, where pollution is more concentrated, the corrosion process occurs at a much higher rate. 

Humidity and Moisture

Water acts as a catalyst for other corrosive agents. In humid environments, moisture remains on the steel surface, activating corrosive agents. When combined with salt or industrial pollutants, the zinc layer deteriorates faster.

Galvanized steel in constant moisture or high humidity, such as in coastal or tropical regions, corrodes at a much higher rate compared to drier climates. Galvanized steel corrosion accelerates significantly when relative humidity exceeds 60%, with the highest rates around 80% or more. 

温度

Temperature has a minor impact on galvanized steel’s lifespan. It can withstand temperatures from -40°F to 194°F without major issues. However, temperatures above 392°F can degrade the zinc coating, exposing the steel to corrosion. This is why galvanized steel is unsuitable for food heating applications.

Here are specific scenarios where galvanized steel is prone to corrosion：

• Acidic foods or beverages: Containers for acidic substances like lemon juice or vinegar, which accelerate corrosion of the galvanized layer.
• Salt spray environments: Steel structures near the ocean or exposed to road salt are highly susceptible to accelerated corrosion from salt.
• Industrial exhaust gases: Galvanized steel near factories or power plants are exposed to corrosive gases like sulfur dioxide and nitrogen oxides.
• Fertilizer storage: In fertilizer storage areas, ammonia and chlorides in the fertilizer can speed up corrosion.
• Animal enclosures and shelters: Contact with animal waste, especially ammonia in urine, can cause corrosion in galvanized steel.
• Acid rain exposure: Areas with frequent acid rain will see a gradual erosion of the protective zinc layer on galvanized steel.
• Prolonged contact with chemical cleaners: Using acidic or alkaline cleaners can corrode the galvanized surface over time.

Internal Factors Prevent Galvanized Steel From Lasting

Galvanizing Process

The galvanizing method impacts the lifespan of galvanized steel. 溶融亜鉛めっき provides a thicker, more robust zinc coating compared to 電気亜鉛メッキ, which results in a thinner layer. Thicker coatings offer better protection in harsh environments, while thinner ones may fail faster, especially in corrosive conditions.

Zinc Coating Thickness

The thickness of the zinc coating is crucial to steel’s lifespan. Thicker coatings create a stronger barrier against corrosion, extending the material’s service life, especially in coastal or industrial areas. Thinner coatings degrade faster, particularly in environments with high salt, moisture, or pollutants.

Coating Integrity

The integrity of the zinc coating is vital. Any damage—such as scratches or cracks—exposes the steel underneath, leading to localized corrosion. Maintaining the coating’s integrity ensures the steel remains protected from corrosive elements, enhancing its durability.

How To Extend The Lifespan Of Galvanized Steel?

Use High-Quality Coatings

Opt for galvanized steel with thicker zinc coatings or consider zinc-aluminum alloys. These coatings offer enhanced corrosion resistance, especially in harsher environments.

Avoid Physical Damage

Protect the zinc coating from scratches, dents, or mechanical damage during handling and installation. Exposed steel will rust faster.

Apply Protective Coatings

In highly corrosive environments, consider adding additional protective layers such as paint coatings, clear sealersあるいは passivation treatments to the galvanized surface for extra protection.

Control Environmental Exposure

Whenever possible, minimize exposure to extreme conditions such as high salt levels, heavy industrial pollutants, or extreme temperatures. Choose suitable locations for installation.

定期メンテナンス

Inspect galvanized steel regularly for signs of damage or wear. Clean the surface to remove contaminants like salt, dirt, or pollutants that can accelerate corrosion.

Quality Galvanized Steel for Long-Term Performance

The quality of the zinc coating, such as inconsistent thickness or poor adhesion, also directly affects the lifespan of galvanized steel. When choosing galvanized steel, it’s important to verify that it complies with specifications and is devoid of any imperfections.

At Steel Pro Group, we provide high-quality galvanized steel through standardized production, processing, and installation processes. We offer a range of products, including coils, sheets, and pipes, with various surface treatments and customization options to suit your project needs.