Rapidly Darken Corten Steel in 2 Days

A few days ago, we launched our guide video to quickly rust, darken and protect corten steel in two days.

Below is a text version of the processing tutorial based on this guidance video, combining BROMOCO Network's professional practices with optimised solutions for the BROMOCO range of products. The guide is divided into four core steps with key operational details and scientific evidence.

Step 1: Accelerated Weathering Process

Objective: To produce a homogeneous oxide layer

When you get a piece of raw steel plate, the first thing you need to do is to make it produce a uniform oxide layer. This process often takes months or even years under natural conditions (e.g. mild steel). Too long a time span can often lead to localised contamination or an uneven rust layer due to poor maintenance.

We therefore recommend the use of BROMOCO XL-08 weathering accelerator. It significantly reduces the oxidation time, shortening the process from months / years to hours / days. The resulting finish can be regulated by the following parameters:

Degreasing: Degrease the raw steel with ERW-BD, which will remove industrial oils and other contaminants from the surface of the raw steel.

Pre-treatment: The roughness of the surface determines the final texture. Just an idea here, sand Blasting results in a fine patina, while mechanical sanding creates a rough texture. You can of course choose any pre-treatment method you wish to get a personalised texture effect.

XL-08 Application: Spray or brush application, coverage 20-25 m²/litre. You can activate as many times as required (e.g. spraying with a brine solution) to deepen the oxidation depth.

Monitoring and Termination: Initial results are visible within 1 hour and an industrial grade stabilised rust layer can be achieved in 2 days. Thorough rinsing with water is required after completion and ERW-BD Neutraliser is used to remove residual accelerant and avoid subsequent coating reactions. After this, you need to allow the steel plate to air dry completely for the next step.

Step 2: Heat Treatment (optional process)

Objective: To regulate the colour of the rust layer

We recommend the use of a propane-butane mixed gas spray gun, using an external flame to heat the surface and move it evenly. You may need to move the external flame quickly over a large area before the heat is applied to even out the temperature of the plate to avoid localised overheating and distortion. Heating on one side allows for consistent colour on both sides by heat transfer.

Step 3: Steel Surface Cleaning and Cooling

Objective: To cool the steel plate and remove loose debris

You will need to rinse both sides with clean water until there are no more particles in the running water. Safety tip: Wear insulated gloves and goggles to avoid burns.

Step 4: Protective Coating Seal

Objective: Curing and long-lasting protection of the rust layer and prolonging its service life

Pre-treatment: Ensure that the surface is completely dry and pH-neutral (treat with ERW-BD if necessary).

Parameters: Uniform CT-7571-W coating, coverage about 30-35㎡/litre. Can be brushed, rolled or sprayed. Forms a transparent film after drying, does not change the original colour, provides corrosion resistance and durability of more than ten years. If multiple coats are required, you need to make sure that one coat is thoroughly dry before applying another coat.

Advancement Suggestions and Considerations:

Environmental Adaptability: Humid climate can prolong the reaction time of XL-08, dry areas need to be combined with salt water spray to maintain humidity

Sustainability: The process uses BROMOCO's water-based, environmentally friendly products, which comply with EU VOC emission standards, reducing construction health risks and environmental burdens.

Indoor Application: The process fully meets the needs of indoor applications and environmental emissions. Low odour and low pollutant emissions. The solution was used indoors in the Grand Designs TV show on Channel 4 in the UK and received good results and feedback on its use.