When powder coated, 1.4003-grade stainless steel offers 90% of the corrosion-resistance and longevity of high-grade stainless steels – at a fraction of the cost – and this is its USP for landscape products.
1.4003-grade stainless steel is IOTA’s ‘go-to’ recommendation for painted products in challenging environments, such as public realm and streetscapes.
In addition to 1.4003-grade stainless steel, IOTA offers three other metals with a powder coat paint finish – each at a different price point, and each with their own individual technical performance characteristics. For a comparative analysis of all four metals, click here.
It is widely understood that high-grade stainless steels [most particularly 316-grade, aka ‘Marine-grade’] offer unparalleled corrosion-resistance and longevity. However, there are also common misconceptions about the material science, and how that impacts on specification decisions.
High-grade stainless steels are ‘austenitic’ stainless steels, which contain significant quantities of expensive alloying elements, such as nickel and molybdenum. These expensive alloys have, in fact, quite limited impact on the structural performance of the metal over time. Instead, these alloys serve to reduce the occurrence of non-structural surface discolouration [aka ‘tea staining’], when the metals are used raw and uncoated – as in the ‘brushed’ finish, commonly specified. So the cost of these alloys matters – but really only aesthetically, and only when the Stainless Steel is used raw.
If the product is to be painted, then completely different specification considerations come to the fore.
1.4003-grade stainless steel is a different kind of stainless steel. 1.4003-grade is a utility ‘ferritic’ stainless steel, which lacks the expensive alloying elements used in high-grade, ‘austenitic’ stainless steels. So, if left raw and unprotected in an outdoor environment, 1.4003-grade stainless steel will suffer from superficial surface staining [‘tea staining’] – rapidly, and unattractively. However, the crucial considerations are that:
The conclusion: if a landscape product is to be painted, then painting onto 1.4003-grade Stainless steel offers 90% of the technical performance of High-grade stainless steels – at a greatly reduced cost.
The full benefits of 1.4003-grade stainless steel are discussed in this article within our Specifiers Area: 1.4003-grade Stainless Steel - The Unique Advantages. However, the most important benefits are:
Painting onto 1.4003-grade stainless steel offers 90% of the technical performance of High-grade stainless steels, at a greatly reduced cost. And this is why 1.4003-grade stainless is IOTA’s ‘go-to’ recommendation for painted products in challenging environments, such as public realm and streetscapes.
There is a crucial distinction between superficial surface staining [‘tea staining’], and progressive degradation [‘rusting’].
If lesser steels – such as mild steel or one of the galvanised steels [such as Zintec steel] – are scratched through to bare metal, rusting will commence immediately; and this rusting will be both progressive and structurally significant. Therefore, if damaged, these steels need to have the protective paint finish reapplied as soon as practically possible.
In contrast, and in most environments, if 1.4003-grade stainless steel is scratched through to bare metal, corrosion is typically limited to superficial surface staining [tea staining], rather than progressive degradation [rusting]. So, whilst IOTA would always advise that scratches should be covered, this is not strictly-speaking mandated [and certainly repainting can be deferred to a convenient time].
However, there are exceptions to this rule.
1.4003-grade stainless steel is designed for environments up to C3 – this being defined as:
“Urban and industrial areas with moderate levels of airborne pollutants [such as sulphur dioxide], or coastal regions with low levels of salt salinity”.
In harsher environments than C3 – such as in the presence of chlorides [from coastal salt spray or road de-icing salts] or strong acids – 1.4003-grade stainless steel can experience pitting and localised corrosion; and this localised attack can become progressive. This rusting will still take place at a much slower rate than is the case with mild steel or galvanised steel, but nonetheless the protective paint finish should be restored as soon as practically possible, to ensure maximum longevity.
1.4003 stainless is a joy to work with, and it can be welded as strongly – and finished as beautifully – as any of the other metals discussed here. Although it is classed as a ‘utility’ steel, there need be no aesthetic compromise when using 1.4003 stainless steel.
1.4003-grade stainless steel is stronger than mild steels or galvanised steels, such as Zintec steel, and it is highly resistant to being ‘punched through’. This is a particular issue with aluminium planters, where – in public realm, for example – vehicular impact damage can breach the metal, and cause spillage of the soil / plants etc. All steels, and stainless steels in particular [including 1.4003-grade], tend to absorb such impacts and deform, rather than the metal splitting.
1.4003-grade stainless steel can be used in any of the relatively protected environments recommended for Zintec steel – such as workplace and residential roof terraces, private residential gardens, education and healthcare environments, offices, and many hotel, restaurant and hospitality venues.
In such protected environments, 1.4003-grade stainless steel will be more expensive than Zintec steel, without there necessarily being a compelling argument for the extra spend. However, where budgets allow, 1.4003-grade stainless steel will deliver better performance, and will offer greater ‘peace of mind’.
1.4003-grade stainless steel’s natural home is in the urban public realm, where the cost premium over Zintec steel is manifestly justified. 1.4003-grade stainless steel is suitable for all such environments, such as:
And 1.4003-grade stainless steel is suitable for all landscape products in these environments, such as:
In recent times, Corten Steel has become increasingly popular for these environments and landscape product applications, with very good reason – as discussed here: Corten Steel – The Facts and The Unique Benefits. However, if the surface is to be painted, rather than left raw, then 1.4003-grade stainless steel is the obvious choice.
1.4003-grade stainless steel is more forgiving of poor quality manufacture than Zintec steel. However, delivering poor quality – or marginal quality – products is not what IOTA is all about.
Landscape products in 1.4003-grade stainless steel should be specified to the same manufacturing quality as for any other steel. This includes setting quality expectations on issues such as:
If made properly, the full benefits of 1.4003-grade stainless steel will be delivered, without any aesthetic compromise.
Tea staining is really the only specific technical consideration when specifying 1.4003-grade stainless steel. And, when specifying this metal, it is important also to establish a clear understanding and expectations with the client.
As already explained, and when used in a C3 environment, tea staining on 1.4003-grade stainless steel is neither progressive, nor structurally significant. However, it can look unattractive; and it can be misunderstood, and this can raise concerns. It is not uncommon for us to get a comms from the client along the lines of “the planters are rusting…!” And we have to explain that, actually, they are not rusting – but that, of course, if it is causing an aesthetic issue, then we can arrange for them to be touched up on-site at cost.
IOTA was commissioned to design and build an edge protection solution at elevation, for multiple terraces on the new Fifty Paddington mixed-use building at 50 Eastbourne Terrace, London W2.
The total perimeter length to be protected was 154 Lm, on terraces at the 3rd and 6th floors.
The final solution was based on continuous runs of planters, with integrated balustrades, based on IOTA’s essential multi-sectional design concepts – as described here: Designing Large Scale Planters in Multiple Sections.
IOTA was commissioned to design, manufacture and install bespoke illuminated cladding, planters and benching for the Mercure Paignton Hotel, Paignton, Devon.
IOTA was contracted on the basis of full Design and Build responsibility, and the contracted Scope of Works included:
The cladding works at Mercure Paignton are one example of bespoke architectural metalwork produced by IOTA.
Overwhelmingly the most commonly-specified paint finish for landscape products is polyester powder coating [PPC] – defined as:
“Powder coating is a type of coating that is applied as a free-flowing, dry powder [unlike conventional liquid paint which is delivered via an evaporating solvent]; and the powder coating is typically applied electrostatically and then cured under heat”.
Powder coat painting offers limitless scope for colour customisation, with a flawless surface finish.
Powder coating is both a cost-effective and flexible technology, and it allows planters and landscape products to be supplied in a wide range of colours, and specialist finishes. Powder coating also allows landscape products to be closely coordinated with wider design schemes, brand palettes or building finishes.
To maximise longevity, a powder coated product should be repainted at intervals specified by the paint manufacturer, which are typically every 9-12 years. This need not be disruptive, as it can be done via an in-situ, wet paint spray reapplication.
More detailed information is given in this article in our Specifiers Area: The Benefits of Polyester Powder Coating [PPC].
Speak to IOTA about the potential benefits of powder coated 1.4003-grade stainless steel for your specific project.
