1.4003-grade Stainless Steel - The Unique Advantages

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1.4003-grade Stainless Steel - The Unique Advantages

An argument for why 1.4003-grade Stainless Steel should be much more widely specified for landscape products


Most specifiers are familiar with 304 and 316-grade Stainless Steels, and will know that they are extremely expensive, but have exceptional technical performance in terms of longevity and corrosion resistance. Many will also understand that 316-grade Stainless is aka ‘marine-grade’, as it has a higher degree of corrosion resistance than 304.

What is less well known is that:

  • With 304/316-grade Stainless Steels, a lot of the cost is, in fact, about aesthetics – not about technical performance.
  • 304/316-grade Stainless Steels are ‘austenitic’ stainless steels, which contain significant quantities of expensive alloying elements, such as Nickel and Molybdenum. These expensive alloys have little impact on technical performance, but 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.
  • There are other grades of utility ‘ferritic’ Stainless Steel which will tea stain if left uncoated [which may, or may not be an issue, as the tea staining is not structurally degrading the metal]; and these other grades of Stainless Steels can still offer 90% of the technical performance of austenitic steels, at a greatly reduced cost.

Type 1.4003 Stainless is one such utility ‘ferritic’ stainless steel. Even if only on grounds of cost, 1.4003 Stainless Steel has huge merit for landscaping products [say, planters] in those situations where:

  • The planters will be paint finished, budgets are constrained, but client expectations of performance and longevity are exceptionally high – for example, larger commercial projects. In these cases, Galvanised Mild Steel [such as Zintec] may not be good enough, but equally it is almost never cost-justifiable to paint finish 304/316 Stainless Steels. 1.4003 Stainless offers a third, and often better, option.
  • There is a high chance of damage to the paint finish – for example: public realm and other high traffic areas. In these cases, it is often cost-justified to grade-up from Galvanised Mild Steel to 1.4003 Stainless Steel; as, if painted 1.4003 Stainless is scratched through to bare metal, it will tea stain but will not corrode and / or degrade.
  • The planters will not be seen [in which case, non-structural surface tea staining is not an issue], but they still need to last and be maintenance-free – such as on a roof.  

In these kind of situations, 1.4003 Stainless Steel can often provide the ‘optimal’ trade-off between technical performance and cost.

There are also other arguments in favour of 1.4003 Stainless Steel – as fully described below.  

For further information, refer to these manufacturer data sheets,  from which the quotations in italics below are extracted.

Aalco Metals 1.4003 Datasheet

Righton Blackburns 1.4003 Datasheet




The prices of different metals fluctuate, and often not in sync. Also the material cost is only one component of the total cost of fabrication [the other costs include labour, machine time, energy, manufacturing consumables etc.]. And these other costs are not necessarily constant [Aluminium, for example, requires highly skilled welding, and that is one of the reasons why it is expensive]. 

So it is hard to be definitive. However, as a rough guide, the price for a given landscaping product might vary as below, assuming all are painted with a Polyester Powder Coat [PPC] finish. Prices are shown as a % uplift from zinc-electroplated mild steel [Zintec], which will always be the cheapest fit-for-purpose option.  

Zintec Steel PPC               100
1.4003 Stainless PPC       115 - 120                             
Aluminium PPC                 120 - 140
304 Stainless PPC            circa. 175
316 Stainless PPC            circa. 200

So 1.4003 Stainless is, in fact, the second cheapest option, and cheaper than Aluminium. Yes, 1.4003 Stainless is 15% to 20% more than Zintec – but it is at least 40% cheaper than 316 Stainless.

So 1.4003 Stainless is very keenly priced. And, as described above, 1.4003 Stainless can often provide the ‘optimal’ trade-off between performance and cost.   

Corrosion Resistance

“1.4003 Stainless has 250 times greater corrosion resistance than Mild Steel”.

That is not a typo. 250 times is correct…!

So, with 1.4003 Stainless PPC, if the PPC layer[s] are scratched through to the bare metal below, then it doesn’t need to be fixed, unless due to aesthetic considerations. So, for example, if the damage is not visible, then it can be ignored – nothing bad will happen from a structural standpoint.

Therefore, as described in Section A, it is often cost-justified to grade-up from Galvanised Mild Steel to 1.4003 Stainless Steel, where there is a high chance of damage to the paint finish – for example: public realm and other high traffic areas. 

Weldability and Finish

“1.4003 Stainless has a fine-grained microstructure which reduces grain growth in the heat-affected zone, and allows for high integrity welds”.

In plain English, 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.

Strength and Stiffness

“1.4003 Stainless offers higher strength than, and equal structural stiffness to, Mild Steels. It also offers greater impact and energy resistance than Aluminium.  It behaves much like austenitic steel in that it gradually yields and does not show a definite yield point”.

1.4003 Stainless is stronger than Mild Steels, such as Zintec, 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.

Coating and Painting

“1.4003 Stainless provides good corrosion resistance and excellent abrasion resistance, hence does not need coating or painting systems to be applied for performance reasons.  However, for aesthetic reasons, it [is most often] desirable to apply paint. It has exceptional under-paint corrosion resistance and will continue to resist corrosion even where the paint coat has been damaged”. 

As already mentioned above, 1.4003 Stainless does not need to be painted, except for aesthetic reasons. And, if the paint finish is damaged, it does not need to be repaired for performance reasons.


At IOTA, we consider the case for 1.4003 Stainless, in many situations, to be compelling; and through this article we hope to ‘spread the word’.

1.4003 Stainless will be quoted as an option whenever we are pricing a job where we feel that it should be considered [typically for larger commercial projects]. To the benefit of all players within the UK landscape industry [clients, architects / specifiers, and manufacturers, such as ourselves], we feel that 1.4003-grade Stainless Steel should be much more widely specified for landscape products, than has been the case to-date.

Contact IOTA T. 01934 522617