Avoiding Costly Mistakes: Common Errors in the Application of Corten Steel

Song
May 28
3 min read

Updated: May 30

Every now and then, we get commissions from clients to fix up damaged Corten or weathered steel building materials. Mostly these are down to homemade products oftern found on the Internet causing catastrophic and somtime irriversable damage of the metal. In this section, we're going to look at a few examples of when Corten steel and weathering steel have been used wrong and how to avoid making the same mistakes.

Case 1: Improper Processes and Use of Improper Accelerants and Coatings

Wooden beams frame a rusted corten steel surface with textured brown and blue corrosion. The setting is industrial, with no text visible.

In this example, the client used homemade Internet-based "cocktail" weathering accelerator to accelerate the patina formation process. Then a critical technical error occurred:

The uncontrollable nature of homemade mixtures makes it difficult for customers to rely on life experience to judge the extent of chemical reactions or to take the correct action.
Once the desired level of weathering has been achieved, the "cocktail" should be rinsed off.
Neutralise with ERW-BD Neutraliser to avoid residues of the "cocktail" continuing to act on the surface.

What went wrong?

The customer didn't rinse off the liquid and neutralise it after using the homemade "cocktail" weathering accelerator to get the right level of weathering. Instead, they left the agent to dry on the surface and then directly used a varnish that wasn't suitable for corten steel. The varnish didn't do a great job of stopping water vapour, which led to the cocktail being reactivated within the varnish layer. The rusting process carried on under the varnish layer and eventually got through from the inside. This caused the surface to blister and form uneven corrosion patterns, which meant that the plate had to be scrapped.

Lesson learnt:

Always use XL-08 Professional Rusting Agent. This has been proven in numerous experiments to be stable and controllable, both in terms of the rate and effect of rusting, and in terms of the ability to be neutralised after rusting.
Always neutralise and clean steel surfaces after using the XL-08 accelerator to stop the corrosion process.
As soon as the patina reaches the desired aesthetics, end the weathering and apply the correct protective coating such as BROMOCO CT-7571-W.

Case 2: Excessive Use of Weathering Accelerators

Five rust-colored metal squares on a white, textured surface with a wood accent and lace fabric, creating an industrial vibe.

Some users use multiple or excessive amounts of accelerator in an attempt to ‘perfect’ the patina. However, overuse can lead to:

Uneven oxidation patterns resulting in spots or scars on the surface.
Damage to the steel structure in some areas due to severe corrosion.

Best practice:

Use accelerators carefully and strategically as recommended by BROMOCO.
Monitor the development of patina in stages.

Rusty metal surfaces with text labels: Left reads "WRONG WAY," right reads "RIGHT WAY." Right is smoother, less rusted. Wrench in background.

Case 3: Weathering Using Homemade Methods

Two rusty metal sheets side by side on a dirt ground, showing uneven orange and grey patterns, with a metallic frame beneath.

Some of our customers opt for the weathering method popularised on the web, using a salt and vinegar solution sprayed on Corten steel or weathering steel plates to weather them. The end result is this.

What went wrong?

Salt and vinegar solutions do react chemically to Corten steel and weathered steel surfaces. However, this solution does not provide a stable chemical reaction and lacks the ability to sustain the reaction. The vast majority of laymen or inexperienced users of this method suffer from uneven chemical reaction, difficulty in determining the degree of weathering, and an inability to gauge the exact amount to be used. This further contributes to the deterioration and obsolescence of Corten or weathering steel.

Lessons learnt:

Use the BROMOCO XL-08 Weathering Steel Accelerator and follow the BROMOCO recommended process for weathering.
Carefully evaluate the practical effects of homemade solutions, especially when chemical reactions are involved.

Case 4: Use of Incompatible Protective Coatings

Modern building facade with stone and rusted metal panels. Cleaning equipment labeled "torik" is on a patio. Tree and field in the background.

Many of our customers have mentioned in their enquiries that they would like to use a universal building materials varnish or car wax for sealing and protection. However these are not suitable for Corten steel and weathering steel. Incompatible coatings may be: