Understand the qualities of corten steel

Corten steel is designed to rust – and it is precisely this rust layer that protects the steel from corrosion. However, during the first few months, the steel will release rust water, especially in wet weather.

This is particularly important to bear in mind if corten steel is placed directly on wooden decking or light-colored paving, as the rust water can cause unwanted marks and discoloration.

The problem: The rust water can leave dark red or orange stains – which can penetrate the surface of wood and be difficult to remove from tiles, especially porous materials such as concrete or limestone.

Placement and Drainage: Avoid Water Runoff Over Wood

When using corten steel – for example in planters, edging, or screening – proper setup is important to avoid direct contact with the surface beneath.

We recommend:

• Choose models with a bottom plate, legs, or wheels, so water can drain away and doesn’t pool underneath the product.
• Use a temporary base (such as a painter’s cloth, weed control fabric, or plastic tray) under the product during the first few weeks.
• Ensure a slight slope or drainage so that rust water doesn’t remain stagnant or run across wood or tile surfaces.

These measures significantly reduce the risk of rust stains and discoloration.

Avoid staining – start the weathering process elsewhere

A smart trick is to let your corten steel pre-weather somewhere else – for example in the garden, on grass or gravel – for a couple of months.

Once it has developed its stable rusted surface, it will release significantly less rust runoff.

This is especially a good idea if you plan to place corten steel:

• On newly treated wooden decking
• On light or porous tiles

That’s why we recommend purchasing your planters or fire pits well in advance – so they can patinate before being moved to their final location.

Protection of the surface beneath

If you choose to place corten steel directly on a terrace or paved surface, be sure to protect what's underneath:

• Treat wooden surfaces with oil or wood preservative to make them less vulnerable to rust runoff.
• Use hidden zinc trays, membranes, or plastic mats under the product to catch runoff.
• Avoid flat areas and joints where water can collect between the steel and the surface – this is especially important near corners and edges.
• On tiles: Make sure the product doesn’t cover joints where rust water can seep down and leave stains.

Select materials wisely

The type of surface material plays a key role in how resistant it is to rust runoff:

• Wood types like cumaru, ipé, and larch are dense and naturally oily, making them more resistant than, for example, pressure-treated pine.
• Tiles made of ceramic, granite, or high-fired clinker have smoother, denser surfaces than concrete tiles or natural stone – and are therefore less prone to discoloration.

The denser and more treated the surface is, the easier it is to keep it free from rust stains.

Alternatives and solutions

At byJEMA, we design solutions that combine both aesthetics and functionality:

• Choose planters in corten steel with adjustable feet, legs, or wheels – minimizing direct contact with the surface.
• Consider our galvanized or black powder-coated variants if you want the same form and function – but without the risk of rust stains.

This gives you the freedom to use steel products on both wood and tile surfaces – completely worry-free.