Using stainless steel in construction has many benefits, especially within the Australian environment. Steel proves exceptionally valuable in situations where structures endure static and dynamic loads, as is its remarkable resilience against tension and compression. Moreover, when engineers design steel components specifically for Australian conditions, it becomes imperative to include corrosion limits that factor in aspects such as duty, steel exposure, and the structure’s intended lifespan. The Australian Standard AS 4312 Atmospheric corrosion zones in Australia, does just this.
AS 4312 Atmospheric Corrosion Zones in Australia
When designing steel structures, the location of the structure should be considered and cross-referenced against the Australian Standard AS 4312 Atmospheric corrosion zones in Australia. Stainless Steel has an advantage over mild steel and galvanised steel as it doesn’t need the same corrosion limits and has higher strengths, meaning the steel can have smaller cross sections while having the same mechanical properties.
| Corrosivity Classifications as Described in AS 4312 | ||||||
| Category | CX | C5 | C4 | C3 | C2 | C1 |
| General Description | Severe Surf Shore Line | Surf Sea Shore | Calm Sea-Shore | Coastal | Arid/Urban | Dry Indoors |
Source: The Standards Australian International
Of particular interest in AS 4312:
Appendix F – Guidance on Corrosion Protection, which lists the Corrosivity of a location based on the Distance from the Ocean / Sea. The standard states that:
- C5 – Newcastle, NSW
- C4 – Victor Harbour, SA
- C3- Port Phillip Bay, VIC
How is stainless Steel Corrosion-Resistant?
Stainless steel is a term that is used to describe corrosion-resistant steel that contains an element called (Cr). Chromium’s properties provide protection against oxidation (corrosion), which means it has a significantly low rate of corrosion. Adding other elements to the stainless steel at manufacturing can then provide different mechanical and chemical properties. While these elements can be expensive, the cost-benefit is they make the life of stainless steel significantly longer. These properties improve the overall performance of Stainless Steel in that environment and therefore increase the life of the asset consistent with the requirements under ISO 55000 Asset Management Standards.
An example of the cost-benefit of stainless steel wire compared to galvanised wire:
Stainless steel is still performing whereas galvanised has corroded, rusted with broken wires and is no longer safe and requires replacement.
There are often differences in construction environments, asset duties and design life, and design engineers need to consider all of these when specifying materials. Within the stainless steel family, there is a specification that can meet all the construction requirements. Therefore, not all stainless steels are the same.
Stainless Steel Grades
Different grades of stainless steel can have similar mechanical properties but have slightly different corrosion-resistant properties based on their chemical composition. By varying the chemical composition of elements like chromium (Cr), nickel (Ni), Molybdenum (Mo), Copper (Cu) and Titanium (Ti), you can greatly improve the performance in different working environments.
The two most common grades of stainless steel are classified as the following:
| Common Name | UNS No. | Forms Available | C | Cr | Ni | Mo | Typical Applications |
| 304 | S30400 | Sheet, Coil, Plate, Bar, Pipe, Tube | 0.05 | 18.5 | 8.5 | Used for architecture, food processing, domestic sinks and tubs and deep drawing applications. | |
| 316 | S31600 | Sheet, Coil, Plate, Seamless and Welded Tube and Pipe | 0.05 | 17.0 | 11.0 | 2.1 | higher corrosion resistance for marine equipment. Can be welded up to 3mm without subsequent heat treatment. |
TABLE: COMMON AUSTENITIC STAINLESS STEEL GRADES AND THEIR APPLICATIONS (Source: ASSDA)
Design considerations
When completing your design details, you should consider those parts of your structure that are designed to have a wet surface as well as the soil conditions. Soil Testing should provide sufficient details as to the corrosivity and porosity of the ground and therefore help with the material of construction selection. It is also important to select the right Stainless Steel to ensure your construction is “Built to Last”.
Material Scientists are a great source of information to better understand a material’s properties and how the material will behave under different conditions. Our industry association ASSDA (Australian Stainless Steel Development Association) have resources that can help you select the right material for the applications. Here at SSWM, we are Australia’s largest stockists of stainless steel wire and mesh, providing an extensive stock range of stainless steel and mesh products.
Contamination and how to avoid it
Stainless steel can be contaminated by carbon steel which will lead to corrosion.
Supply Chain: Contamination can occur during manufacturing and along the supply chain. Clean storage and quality packaging are important to ensure there is no contamination.
Fabrication:
Ideally, a fabricator will have a dedicated workshop and tools for stainless steel only.
Contamination can be picked up from:
- Grinding wheels, wire brushes and linishing belts
- Steel storage racks
- Tooling used with other metals
- Contamination from grinding or welding sparks from nearby carbon steel fabrication
Stainless Steel: the lasting decision and the lasting look
It is recommended that when stainless steel is to be used for external purposes that it be electropolished. Refer to our Care & Maintenance page for further information.
In a world that is focused on sustainability, the natural choice for construction is a material that will last and that can be 100% recycled. For further insight refer to our blog “Examples of Stainless Steel Wire & Mesh in Construction Projects.”
