does galvanised steel ever rust

Does galvanised steel ever rust? The short answer is yes, but only under certain conditions. Galvanised steel is one of the most reliable and cost-effective corrosion-resistant materials available. It's widely used in construction, industrial settings, and outdoor applications. However, while the zinc coating offers excellent protection, there are some caveats. Sustained exposure to harsh environments, physical damage, and chemical reactions can compromise it. Without proper maintenance and installation, its durability can be significantly reduced over time.

At Clickmetal, we don't just supply premium-quality cut-to-size metal solutions. With over 70 years of experience in the industry, we understand how it performs in real-world conditions. Understanding how and when galvanised steel rusts is crucial for ensuring long-term performance. This page explores the science behind its corrosion resistance. It covers what factors can accelerate rusting and recommends maintenance tips to extend its lifespan. So, are you tackling a DIY project, getting materials for industry, or building strong outdoor structures?

Read on for valuable tips and tricks to safeguard your investment.

Can Galvanised Steel Rust? Understanding Corrosion Risks

Despite its superior rust resistance, galvanised steel is not immune to corrosion. Environmental exposure can compromise the protective zinc layer. Chemical reactions and physical wear and tear may also reduce its effectiveness. Under certain conditions, even the best-coated galvanised steel may begin to rust over time.

Three Main Causes of Rust in Galvanised Steel

Exposure to Saltwater and High Humidity

Galvanised steel is commonly used in marine and coastal environments. However, exposure to salt-laden air accelerates zinc corrosion. Over time, the protective coating depletes, exposing the steel beneath.

A UK government study found that galvanised steel in seaside structures degrades faster than in inland areas.

Chemical Exposure and Industrial Pollution

Acid rain, factory emissions, and high levels of sulphur dioxide in urban areas contribute to faster zinc corrosion. Industrial pollutants greatly impact metal longevity in major UK cities like London and Birmingham, so additional protective measures are often required.

Galvanised steel might need extra coatings like epoxy or powder coating to last longer in places with high chemical exposure.

Physical Damage and Galvanic Corrosion

Scratches, mechanical wear, and improper handling can remove or weaken the zinc layer, exposing the steel to rusting agents. Once exposed, rust spreads rapidly unless treated.

Galvanised steel should not be placed in direct contact with copper or carbon steel. These metals accelerate galvanic corrosion, leading to localised rusting.

Why Galvanised Steel Resists Rust & How It Works

Galvanised steel is coated in zinc through a process called hot-dip galvanisation. This process provides a sacrificial layer of protection. Untreated steel rusts easily when it's exposed to air and moisture. On the other hand, galvanised steel is protected by zinc, which helps stop oxidation. The coating shields the underlying steel from corrosive elements and reduces the chances of rust formation.

Three Ways Zinc Protects Galvanised Steel from Rusting

Physical Barrier Against Moisture and Air

The zinc layer forms a dense, protective coating that prevents direct exposure to oxygen and water. Without this exposure, the oxidation process that leads to rust cannot occur. This is why galvanised steel performs well in outdoor and industrial environments.

Sacrificial Corrosion Protection

Zinc has a lower electrochemical potential than steel, meaning it corrodes before the underlying metal. This sacrificial property protects the steel. If the surface gets scratched or chipped, the zinc around it keeps shielding the exposed steel and slowing down rust formation.

Self-Healing Properties in Certain Conditions

Where zinc hydroxide can form, such as in areas with controlled humidity, the coating can naturally "heal" minor scratches. This self-repair mechanism lowers localised corrosion and helps the steel structure last longer.

The Health and Safety Executive (HSE) says that galvanised steel is far better in industrial settings than untreated steel. They report that its corrosion resistance lasts decades longer than when left under normal conditions.

Where Galvanised Steel Performs Best (and Where It Doesn't)

Galvanised steel is popular because it's versatile, durable, and affordable. This makes it a staple in many industries. However, while it excels in most conditions, there are situations where it may not be the best option.

Best Uses for Galvanised Steel

Outdoor Construction & Infrastructure

It is common for roofing, fencing, and building frameworks due to its weather-resistant properties. For more on this, discover why galvanised steel is ideal for outdoor structures.

Industrial & Agricultural Applications

Used in warehouses, storage facilities, and farm buildings, where moisture exposure is moderate but not too high.

Transport and Automotive Uses

Galvanised steel is standard in lorry bodies, trailers, and vehicle chassis. Its resistance to road spray and environmental wear is a significant advantage.

When Galvanised Steel Might Not Be Ideal

Fully Submerged Marine Environments

Extended exposure to saltwater accelerates zinc depletion, leading to faster corrosion. When fully submerged, water quickly removes the zinc layer that protects galvanised steel. Ultimately, the process accelerates corrosion and reduces the steel's lifespan. This is especially problematic in coastal infrastructure, piers, and underwater pipelines. Stainless steel or specialised marine coatings are better alternatives for long-term submersion.

High-Temperature Applications

When temperatures rise above 200°C, the zinc layer starts to degrade, weakening its ability to protect the underlying steel. At even higher temperatures, zinc can vaporise. This process strips the steel of its protective barrier entirely, making it vulnerable to oxidation. This is particularly apparent in industrial furnaces, exhaust systems, and heat-intensive manufacturing environments. For applications facing extreme heat, consider using heat-resistant alloys or stainless steel.

Order Cut-to-Size Galvanised Steel Today

Get durable, corrosion-resistant galvanised steel delivered fast and cut to your exact size.

Galvanised steel offers long-lasting protection against corrosion. However, its success relies on selecting high-quality materials and ensuring precise cuts. A poorly sized sheet or bar can lead to unnecessary modifications, delays, and material waste, so getting it right the first time is essential.

At Clickmetal, we make it easy to order premium galvanised steel with the exact dimensions you need. No need for extra cutting or adjustments – simply order, receive, and get to work. Whether you need a single sheet or bulk quantities, our fast 3-5 day delivery keeps your project moving. Plus, with our expert team on hand, we'll help you find the best options for your application. Don't waste time with off-the-shelf cuts – order precise, cut-to-size galvanised steel today.

Shop now, get in touch, or call us on 01794 526090 to speak with an expert.