Corten Steel Planters: Are they Worth it?

Otherwise known as weathering steel, Corten steel has been used to construct a whole host of hardy architectural feats, including buildings, bridges and the catenary gantries used to support the electric cables that hang over our train lines. As such, it’s safe to say that this impressive material has both the tensile strength and the longevity to make it in your garden.

But exactly how long does it last? What is so special about Corten steel planters? And is it worth spending more for the added benefit of extreme durability and low maintenance?

Weathering steel tends to be more expensive than other types of steel, like mild steel and galvanised metal options. Nevertheless, it also tends to last much longer, making it cheaper over time. This cost-to-lifetime ratio is just one of the many reasons that weathering steel is an ideal investment for your landscaping project or garden.

HOW DOES CORTEN STEEL WORK?

Before we begin discussing the merits of Corten steel in more detail, let’s look at the oxidation process. This is what gives our planters their unique colouration, with hues ranging from deep browns and russet reds to earthy oranges and bronze-like tones. However, oxidation is about so much more than aesthetics.

Unlike other metals, Corten steel undergoes a process of controlled oxidation when exposed to outdoor air and moisture. In other words, the rust-like layer that forms on the surface serves to stabilise your planters and protect them from further damage, rather than weakening them. This means that Corten ages incredibly slowly. Of course, some material loss is inevitable over time – particularly as a result of wear and tear and atmospheric pollution – but this process is hundreds of times slower than with other types of steel.

SO, HOW LONG DO CORTEN STEEL PLANTERS LAST?

You may have noticed that Weather It offers a generous five-year warranty on all of its Corten steel planters. This is because we feel extremely confident in our long-lasting products.

It can be difficult to predict exactly how long our planters will last, as exact longevity depends on a series of specific conditions. That said, we can say that it’s safe to expect your planters from Weather It to become a long-term feature in your garden for years to come.

You may have heard that weathering steel can last for anything up to 120 years, given the right conditions. Whilst this is technically true, it’s important to take several key factors into consideration:

Placement

As explained above, the rust-like layer that forms on the surface of your planter is absolutely essential to its longevity. It is designed to develop its protective oxide layer upon exposure to oxygen and humidity in the air. Therefore, any steel placed below the ground will corrode at a different rate than above the surface. This means that the lifespan of our planters and garden edging products will depend on placement.

Patina

The patina that Corten steel develops is also completely unique to local conditions, with soil and atmosphere also impacting the natural corrosive process. There have even been some instances in which Corten structures have had to be taken down because the local climate simply wasn’t conducive to a protective layer developing, even after many years. Take the Omni Coliseum in Atlanta, for example, which failed to rust even after 25 years. Luckily, with the UK climate, this needn’t be a concern, as the most favourable conditions consist of alternating wet and dry weather – something we’re by no means short of!

Thickness

Most of our planters are made from structural-grade Corten steel measuring 2 mm in thickness, meaning they should remain fit for purpose for an extremely long time. Indeed, many companies report that they can last for up to 25 years. Moreover, most material loss will actually occur in the first few years and is so minimal that you will barely notice it.

Whilst we do offer bespoke planters made from Corten steel of up to 6 mm in thickness, these options can prove more expensive, so it’s best to consider the amount of time you intend to use your planters before ordering. For most domestic gardening projects, two millimetres should more than suffice.

What can I do to increase longevity?

Because our Corten steel planters are designed to be incredibly low maintenance, there’s little you need to do to keep them looking their best, beyond avoiding high-chloride and high-salinity environments. However, if you live near the coast, the sea salt in the air could prove quite damaging, which is why we recommend hosing your planters down after a heavy winter storm.

Weathering steel is designed to be left unfinished, requiring no paint, wax, lacquer or other types of coatings or finishes. However, in environments where it cannot maintain an ideal wet-dry cycle to establish its protective layer – for example, on the inside of planters – you may wish to seal the inside with a bitumen, damp-proof membrane. This is only worth it financially for the thickest steel planters expected to last more than a few decades.

Are Corten steel planters worth it?

In terms of cost, Corten steel will give you the best value for money of all available metal planters. They last for years and don’t require any maintenance. In contrast, mild steel has a shorter lifetime, meaning that, although it is the cheapest sheet metal option, it won’t last as long as choosing the Corten option.

In terms of aesthetics, it’s difficult to find anything comparable to the natural beauty of weathering steel, particularly when considering how your planters will look over a long period of time and particularly when you opt for the handmade options available at Weather It. To find out more about what we have to offer, browse our range or contact the sales team at sales@weather-it.co.uk or on 0121 824 5700 to answer any questions or discuss any bespoke requirements.