3 Essential Maintenance Tips to Preserve Your Weathering Steel Finish

Song
Dec 1
3 min read

Weathering steel, often known by the trademark COR-TEN steel, is prized for its unique ability to develop a stable, rust-like appearance that protects the metal underneath from further corrosion. This makes it a popular choice for outdoor sculptures, architectural features, bridges, and even garden structures. However, while weathering steel is designed to withstand the elements, it still requires proper maintenance to preserve its distinctive finish and structural integrity over time.

In this post, we will explore 3 key maintenance tips that help you keep your weathering steel looking its best and performing well for years to come.

Modern building with weathering steel facade, red flowers in black pots, and a rustic metal accent. Trees and houses visible in background. — Image taken from our Toronto project

Understand How Weathering Steel Works

Before diving into maintenance, it’s important to understand the science behind weathering steel. Unlike regular steel, weathering steel contains alloying elements such as copper, chromium, and nickel. These elements cause the steel to form a protective rust layer when exposed to air and moisture. This rust layer acts as a barrier that slows down further corrosion.

The protective patina develops over several months and varies depending on the climate. In dry environments, the patina forms quickly and remains stable. In humid or coastal areas, the process takes longer and may require more attention.

Knowing this helps you appreciate why maintenance focuses on preserving the patina rather than preventing rust altogether.

Tip 1: Keep the Surface Clean and Free of Debris

Worker in a yellow helmet and vest sprays water on weathering steel panels at a construction site with concrete walls, under a clear blue sky. — Image taken from our Cyprus project

One of the simplest but most effective ways to maintain weathering steel is to keep its surface clean. Dirt, leaves, bird droppings, and other debris can trap moisture against the steel, accelerating corrosion beyond the protective patina.

How to clean weathering steel:

Use a soft brush or cloth to remove loose dirt and debris regularly.
For stubborn grime, rinse the surface with clean water and BROMOCO ERW-BD. This is a cleaning agent and degreaser developed independently by BROMOCO for use on any fragile or sensitive surfaces. Avoid harsh chemicals or abrasive cleaners that can damage the patina.
After washing, allow the steel to dry completely to prevent moisture buildup.

Why this matters:

Cleaning prevents the buildup of contaminants that can cause uneven rusting or staining. For example, if leaves accumulate in crevices, they hold moisture and create localized corrosion spots that weaken the steel.

Regular cleaning also helps you spot any areas where the patina might be compromised, allowing you to address issues early.

Tip 2: Manage Water Drainage and Avoid Trapped Moisture

Red brick pavement with a large weathering steel planter filled with stones. A red circle highlights darkened bricks, suggesting wear or damage.

Water is the main factor that influences the rusting process in weathering steel. While the steel needs some moisture to develop its protective layer, standing water or trapped moisture can cause excessive corrosion. Rainwater runoff may also carry rust particles, contaminating nearby surfaces such as concrete, glass or stone.

What to check and fix:

Ensure your weathering steel structure has proper drainage. Water should flow off surfaces quickly without pooling.
Sealed using the BROMOCO CT-7571 weathering steel protector to isolate moisture and contaminants.
For existing stains, please clean using ERW-BD, a mild detergent suitable for outdoor surfaces.

Tip 3: Use Professional Surface Protectors to Safeguard Weathering Steel

Man in black jacket applies stencil on weathering steel in warehouse. Shelves with bottles and boxes in the background. — Image taken from our Scottish project

Even with good care, weathering steel can suffer from scratches, dents, or areas where the patina is damaged. Rather than passively repairing weathered steel, it is preferable to take proactive measures to protect it. Protect your weathering steel with BROMOCO's CT-7571. This creates a strong, natural-looking layer that stops rust, stains and damage, even in tough conditions. *Do not use varnish or lacquer!!!

Why timely protect matters:

Prompt attention prevents small issues from becoming large problems. For example, a scratch on a weathering steel bridge railing can quickly expand if moisture penetrates beneath the patina.

Additional Tips for Long-Term Care

Avoid contact with dissimilar metals. When weathering steel touches metals like aluminum or stainless steel, galvanic corrosion can occur, damaging the finish.
Limit exposure to saltwater. Coastal environments accelerate corrosion. If your steel is near the ocean, more frequent inspections and cleaning are necessary.
Monitor color changes. The patina should develop a consistent reddish-brown color. Dark spots or greenish hues may indicate corrosion issues or contamination.

Maintaining weathering steel is about respecting its natural process and supporting the protective patina that makes it unique. By keeping the surface clean, managing drainage, and sealing surface timely, you can enjoy the beauty and durability of weathering steel for decades.