Our Relatively Clean Air – We’re Not Off the Hook

When compared to other cities such as those in India, Bangladesh and China, the air in Australian cities is relatively clean.

But like anywhere else in the world, Australia’s metropolitan areas can feature poor air quality thanks to the pollution provided by motor vehicles, industry and human activity. And sometimes it can occur on a scale that can rival the worst recordings in the world, especially during natural disasters like bushfires, such as when the Australia’s capital, Canberra, reached position 4 in the live air quality (AQI) city rankings in January 2020.

Beyond exceptional and rarer events like the fires, Australian cities are unique in their experience with air contaminants thanks to a phenomenon that can contain air pollution in one area for a lot longer than would be considered normal before dissipation, especially on the eastern seaboard: an ‘airshed’.

An airshed is typically defined as a part of the atmosphere that ‘performs in a coherent way with respect to the dispersion of emissions.’

But the term is also applied to a ‘geographical area where local meteorology and topography limit the dispersion of pollutants away from the area.’ For air pollution reporting, an agency like the Environment Protection Authority (EPA in each state) will also use the term to distinguish a boundary of a town or its suburban area, or a council locality in order to report air pollution level across the same area consistently over time.

If you look at a map of Australia, you’ll see that most capital cities are located in a coastal location.

On the Eastern Seaboard, these metropolitan areas are wedged between the sea and the Great Dividing Range, which stretches for more than 3,500km from just north of Cairns in Queensland down to the Grampians in western Victoria. The width of the gap between the mountains and the sea stays fairly consistent all the way down, which creates a long, skinny airshed.

With this, the pollution generated by cities is often blown out to sea overnight or in the early morning, only to return and get trapped against the ranges with the afternoon sea breeze.

What’s in It?

The nine most common air pollutants are ozone, carbon monoxide, sulphur dioxide, lead, nitrogen oxides, particulate matter, carbon dioxide, methane and chlorofluorocarbons. In relation to Australia’s air, ozone, carbon monoxide and nitrogen oxides make up most of the air pollution, thanks to the majority of the country’s vehicular emissions, heavy industries and manufacturing plants being concentrated within the east coast airshed.

How Does This Affect the Construction Industry?

Of all the common air pollutants, a handful that are present in any smog or invisible encroachment of hazardous gases will corrode certain types of metals. The main ones are:

• Ozone — galvanised steel, cast iron, zinc will eventually corrode/break down when exposed to ozone. Zinc in particular is affected by ozone within a matter of days.
• Carbon monoxide — many metals are also susceptible to corrosion if impure carbon monoxide and sulphur compounds combine.
• Nitrogen oxides — when water is present with nitrogen and oxygen, the combination can cause metal tanks and pipework to corrode.

In the construction industry, the use of fasteners is of course core to many projects. For fixing to concrete, most concrete anchors, for example, are made from carbon steel, in either plain or galvanised finishes.

These products are the cheaper option and certified as more than compliant for use in their applications and are therefore used the most compared to stainless steel options.

But considering heightened presence of air contaminants where most of Australia’s construction projects take place—in industrial and non-industrial eastern seaboard cities and within close proximity of the country’s 25,760km coastline—there is an increased need for using fasteners that are more resistant to corrosion.

The construction market is slowly adopting a new attitude towards upgrading their consumables, but there is a long way to go.

Girt by Sea-(linity)

Speaking of coastlines, Australia’s coastline is the sixth longest in the world. And with most of the population living near the coast (60% of the population), corrosion from sea air is also a factor for choosing construction supplies.

And another factor provides a higher corrosion environment in many places in Australia: salinity.

Since European settlement, salinity has become a growing feature of the country’s landscape, caused by the clearing of a large percentage of deep-rooted native vegetation, which helped to maintain ground water levels in a static state by keeping it down.

With the native vegetation removed, the water rises from the water table, evaporates and leaves salt on the surface. This affects a small percentage of each Australian state except Western Australia, where salinity-affected soils cover 70% of the state’s land.

With this, it is not only coastal-based construction projects that need to take salt-derived corrosion into consideration when choosing materials but also in many places inland.

The Resistance Revolution

With corrosion-related factors in mind, those in the construction supplies industry (B2B sellers) are anticipating a change in the way their clients specify and quote jobs in the not-too-distant future.

For some builders, the environmental factors are a big consideration, whether they are choosing products to embellish their value proposition to their clients or whether stainless steel products are specified by an engineer.

As a superior alternative to standard carbon steel, stainless steel from the ‘300 series’ (specifically 304/316) is being adopted as a key corrosion-resistant makeup of construction fasteners. Stainless steel is resistant to ozone, carbon monoxide/sulphur compounds and nitrogen oxides (in fact, a certain % of nitrogen contained within some stainless alloys helps to resist pitting corrosion).

Granted, carbon steel has also been the default choice because of heat treatment and subsequent higher tensile strengths than stainless steel when being embedded or installed or when taking on heavy duty loads. But innovations in the fasteners space have resulted in hybrid products that harness the benefits of both metals.

Bi-metal stainless concrete screw anchors are one such product. Designed to fix metal to concrete, these fasteners are traditionally galvanised or plain carbon steel. A bi-metal version still features carbon steel on the tip for strength during embedment but with a 316 stainless steel loading area (the other 85% up to the head).

What this provides is a high level or corrosion resistance for the exposed head as well as the loading area when moisture penetrates the concrete. These products can of course override the use of standard material compositions as part of a building company’s value proposition when quoting a build — especially when quoting a build on Australia’s eastern seaboard or high salinity-affected zones.

Stainless steel has long been used in the manufacture of expanding anchors (colloquially/proprietorially known as the “DynaBolt”) for medium load applications. Whilst these are excellent for use in marine environments and other places a higher level of salt air and pollution resistance is required, such as handrails and the like at shipping terminals or petrochemical facilities, newer screw type anchors are increasingly surpassing these anchors as the choice of builders due to their ease of installation, higher load capacities and other advantages.

These are just two examples of stainless steel being used to make construction fasteners. There are also screws, hex bolts, matching nuts, set screws, threaded rod and many more.

2020 and Beyond

Although costs might be a little higher for these consumables, many builders are seeing the long-term benefits of using stainless fasteners over standard compositions that override short-term cost savings, in the form of heightened reputation in the market for constructing projects that are designed to withstand corrosive pollution for longer. And with no quick solution on the horizon to ever-increasing air pollutants, stainless steel fasteners are sure to become standard for use by builders in Australia.

References:
EIGA
CSIRO
Ozone Solution
Business 2Community