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Author: J. Rigby

This paper was presented at Corrosion & Prevention 2023.

To achieve sustainability, most governments and corporations have identified three parallel pathways and have each developed their environmental policy, social policy, and governance policy, also known as ESG. This paper will focus on the environmental aspects of sustainability. Embodied carbon emissions are hard to eliminate. Some of our most common building materials – like concrete and steel – require process heat and chemical reactions that can’t be achieved with electricity alone. Without taking a targeted and collaborative action, embodied carbon emissions will be responsible for 85% of the built environment’s carbon emissions by 2050. This study will focus on two ways in which the coatings industry aims to contribute towards a sustainable future:

1. By better protecting built assets, and thus keeping embodied carbon embodied for as long as possible.
2. Limiting emissions of greenhouse gas; improving air quality; and reducing the use of harmful materials.

Project specifiers have a responsibility to select the most appropriate protective systems that provide optimum durability to our infrastructure. Particularly now the carbon footprint of maintenance interventions needs to be considered in a life cycle assessment, the advantages of durable protective systems and the consequent reduced number of maintenance painting interventions will reduce the overall environmental impact.

Keywords: Coating, sustainability, corrosion protection, durability, built environment

This study will focus on two ways in which the coatings industry aims to contribute towards a sustainable future:

1. By better protecting built assets, and thus keeping embodied carbon, embodied for as long as possible.
2. Limiting emissions of greenhouse gas; improving air quality; and reducing the use of harmful materials.

In this discussion the term ‘coatings’ will be used for protective coatings that are used to prevent corrosion. The term ‘paint’ will only be used for decorative paints.  Where the word “carbon” has been used, reference is made to carbon dioxide.

Sustainability is a catchphrase that means something different to each person and a person’s association with that word probably changes depending on the context in which “sustainability” is used in the media. The Oxford Dictionary describes sustainability as “avoidance of the depletion of natural resources in order to maintain an ecological balance”. To achieve sustainability, most governments and corporations have identified three parallel pathways and have each developed their environmental policy, social policy, and governance policy, also known as ESG. This paper will focus on the environmental aspects of sustainability.

Climate Change

To tackle climate change and its negative impacts, world leaders at the UN Climate Change Conference (COP21) in Paris reached a breakthrough on 12 December 2015: the historic Paris Agreement (1). Under the Paris Agreement, to which Australia is a Party, countries are required to communicate their Nationally Determined Contribution.

The Intergovernmental Panel on Climate Change (IPCC) 2022 report Impacts, Adaptation and Vulnerability (2) found that global warming, reaching 1.5°C in the near-term, would cause unavoidable increases in multiple climate hazards and present multiple risks to ecosystems and humans. In their Mitigation of Climate Change 2022 report (3), the IPCC concluded that the world is not on track to limit global warming to 1.5 or 2°C on the basis of current policies.

The breakdown of climate associated with the difference between these two scenarios is likely to result in more demand for heating and cooling. The negative economic impact globally of additional heating and cooling demand is expected to increase fourfold by the end of the century and apply further pressure on eco-systems. The consequences will be long lasting and, in some cases, irreversible.

Society needs to radically transform current unsustainable models of consumption. The Australian Government has introduced the Climate Change Bill 2022 (4). The Bill legislates the nation’s commitment to reduce greenhouse gas emissions by 43% below 2005 levels by 2030, and net zero by 2050. Australia is the world’s 14^th highest emitter, contributing just over 1 per cent of global emissions. Globally, the 1.5°C goal requires net zero emissions by 2050. To achieve this the Paris Agreement requires a balance between emissions and removals of greenhouse gases to be at net zero.

Greenhouse Gas

Greenhouse gas is any gas that has the property of absorbing infrared radiation (net heat energy), thus contributing to the greenhouse effect. Greenhouse gasses emitted by industry in general include carbon dioxide, methane, ozone, and chlorofluorocarbons (CFCs).

Harmful emissions to which the coating industry more specifically contributes are;

• Carbon embodied through production of their raw materials, and the energy used in manufacturing, transport and warehousing.
• Volatile organic compounds (VOC’s) from solvents and coatings which contribute to harmful ozone formation.

Carbon

Carbon is not only emitted during operational life but also during the manufacturing, transport, construction and end of life phases of all built assets.

Operational Carbon

Operational carbon is generated during the normal operation of an asset for lighting, cooling, heating, ventilation and other processes that require electricity.

Basics like improving building insulation, installing LED lighting and automatic controls have long been used to reduce operational carbon, and new buildings are now designed to be highly energy-efficient, with the use of innovative materials and smart technology.

Coatings do not generally contribute to operational carbon of built assets.

Upfront Embodied Carbon

Upfront embodied carbon refers to the greenhouse gas emissions generated during the manufacturing and transportation of materials and throughout the construction phase.

Until this past decade, these emissions have largely been overlooked however since the easy gains have already been made in reducing operational carbon, upfront embodied carbon has attracted an increased focus to help drive further toward net-zero.

Upfront embodied carbon contributes approximately 11% to the total global carbon emissions (5) and will be responsible for half of the entire carbon footprint of new construction between now and 2050, threatening to consume a large part of our remaining carbon budget.

Embodied carbon emissions are hard to eliminate. Some of our most common building materials – like concrete and steel – require process heat and chemical reactions that can’t be achieved with electricity alone. Without taking a targeted and collaborative action, embodied carbon emissions will be responsible for 85% of the built environment’s carbon emissions by 2050 (6).

Sustainability Through Reducing Carbon Emissions

The built environment sector has a vital role to play in responding to the various agreed commitments to reduce greenhouse gas emissions. With buildings currently responsible for 39% of global carbon emissions (5), decarbonising the sector is one of the most cost-effective ways to mitigate the worst effects of climate change (7).

As operational carbon is reduced, embodied carbon will continue to grow in importance as a proportion of total emissions and increased efforts are being made to tackle embodied carbon emissions.

Many government agencies do not have a formal framework to measure and manage carbon throughout a project lifecycle and most of the published data references studies from the built environment.

Lifecycle Assessment

The LCA approach was first defined by the International Organization for Standardization, who developed the ISO 14040 series of standards that provide a systematic tool for the quantitative analysis of environmental loads of a product in its entire life cycle and assessment of their potential impacts on the environment. The LCA can be seen as the “cradle-to-grave” or “whole of life” approach and consists of four main steps:

• Goal and scope – to determine the life cycle of the project.
• Life Cycle Inventory (LCI) – provides possible resources, material and waste list or discharge material during the life cycle of a product.
• Life Cycle Impact Assessment (LCIA) – where the inventory data collected for the various phases of the life cycle are classified into their categories of impact.
• Interpretation – the point at which decisions are taken based on the outcome of the inventory and impact evaluation.

An LCA can also be used for evaluation of the environmental impact of buildings and other large pieces of infrastructure, where the extraction of raw materials and disposal or recycling of materials are also considered.

For the built environment, the life cycle assessment largely needs to consider the use of concrete and steel.

Emissions from Steel Production

At around 1.9 billion tonnes of production per year, steel is the third most abundant man-made bulk material on earth, after cement and timber.

The People’s Republic of China accounts for more than half of global steel production today and – despite high domestic demand – it is also the largest exporter, followed by Korea, Japan and the Russian Federation.

The blast furnace is a major piece of equipment used for primary steelmaking, with this route accounting for 90% of production from iron ore. Secondary (or scrap-based) production is carried out in electric furnaces and is around one-eighth as energy-intensive as production from iron ore, using electricity – as opposed to coal – as the main energy input.

Among heavy industries, the iron and steel sector ranks first when it comes to CO₂ emissions, and second when it comes energy consumption. The iron and steel sector directly accounts for 2.6 gigatonnes of carbon dioxide (Gt CO₂) emissions annually, 7% of the global total from the energy system and more than the emissions from all road freight. The steel sector is currently the largest industrial consumer of coal, which provides around 75% of its energy demand. Coal is used to generate heat and to make coke, which is instrumental in the chemical reactions necessary to produce steel from iron ore. CO₂ emissions are projected to continue rising, despite a higher share of less energy intensive secondary production, to 2.7 Gt CO₂ per year by 2050 – 7% higher than today. Each tonne of steel produced today still results in 1.4 t CO₂ of direct emissions on average (8).

Emissions from Cement Production

Approximately 4.3 billion tonnes of cement was produced in 2021. China was the largest contributor to global production, accounting for about 55% of the total, followed by India at 8%.

The direct CO₂ intensity of cement production increased about 1.5% per year during 2015-2021. In contrast, 3% annual declines to 2030 are necessary to get on track with the Net Zero Emissions by 2050 Scenario. Two key areas need to address carbon reductions by: reducing the clinker-to-cement ratio (including through greater uptake of blended cements) and deploying innovative technologies, such as carbon capture and storage, and clinker made from alternative raw materials. (9).

Steel and concrete are indispensable materials in modern construction and buildings and infrastructure remain a key source of demand. General estimates for upfront embodied carbon from different construction elements for a typical building project are:

• Substructure: 10% to 30% (depending on the extent of basements)
• Superstructure: 40% to 70%

o       Upper floors and columns: 30% to 50%

o       External walls, windows, and external doors: 8% to 25%

• Finishes (including coatings): 4% to 8%
• Building services: 5% to 8%

For other infrastructure like tanks, bunds, roads and bridges, the embodied carbon distribution is somewhat different but it is more difficult to define since they are more variable in design and construction complexity than an average building. However, given the extensive use of concrete and steel in both sectors, useful parallels can be drawn to identify building materials and their proportionate contribution toward carbon emissions.

Carbon Emissions from Coatings

As seen in the example above, the current focus for embodied carbon is on the substructure, upper floors, columns, external walls and windows that represent approximately 70 to 80% of the project’s upfront embodied carbon. Even though coatings only represent a relatively small proportion of overall upfront embodied carbon the coatings industry is subject to a disproportionate share of regulations due to relatively high emissions of volatile organic compounds (VOC) that not only impact air quality but also contribute to greenhouse gasses in the atmosphere.

Unlike steel, and concrete to a lesser extent, it is impractical to reuse or recycle used coatings. The paint and coating industry, typically uses solvents such as toluene, m/p-xylene, butene, butadiene, and acetone in their product formulations.

When coatings go through the curing or drying phase, these VOCs are released from the coating film. VOCs have high vapor pressures (0.01 kPa or more at 20°C (10)), which means they evaporate easily or off-gas in the open air as soon as the coating is applied and, depending on its formulation, may continue to off-gas for months as the coating completes the curing process.

VOC’s are problematic for five main reasons;

• They require synthetic raw materials that come from other production processes that depend on the burning of fossil fuels (11).
• VOCs in paints are usually hydro-carbons so they contribute to the overall carbon footprint.
• They oxidise in the atmosphere to form ozone, also a greenhouse gas.
• VOCs indirectly contribute to the formation of smog and particulate matter (12).

Solvents are often considered environmentally toxic products and affect people, animals, and plants in different ways and VOCs are recognized as causative agents of the sick-building syndrome (13). In short, VOC’s pose a threat to human health and affect the environment and climate change.

Concerns of governments over ground-level ozone formation and regional air quality has promulgated directives in many jurisdictions with some of the most advanced being from Europe and California with respect to solvent emissions. In China, several government initiatives have been introduced to reduce VOC emissions under the 13^th Five-Year Plan. Consequently, industry is required to reduce its emissions of volatile organic compounds (VOCs) in general, and solvents in particular.

Table 1 provides an example of typical volume solids for generic coating groups.

For 2018, the total global paint and coatings market for solvent borne paint was approximately 2390.886 kilo tonnes (14). From that volume, we can extrapolate that this includes approximately 590.91 kilo tonnes of VOC’s.

Table 1: Typical Densities and Solids Contents of Coatings based on ASNZS2312 PUR5 System.

Type of Coating	Density (kg/L)	Solids (Volume %)	VOC (w/w%)
Primer ZRE	2.52	59	15.2
Intermediate, epoxy	1.51	70	19.8
Polyurethane	1.33	60	34.1
Average	1.78	63	23.0

 

VOC’s are not the only issue that make coatings problematic with respect to sustainability. Coatings are however an important tool that help to make infrastructure in general more durable and therefore more sustainable. In the sections below, a deeper focus is placed on additional issues that are normally considered problematic with coatings and what the industry is doing to make coatings more sustainable.

Paint has been integral with human history starting from early rock paintings through to modern surface coatings.

History of Coatings

In early rock paintings humans have expressed themselves starting over 40,000 years ago using mineral-based pigments. Nawarla Gabarnmang has the oldest radiocarbon dated painting, in Australia.

It is a large rockshelter located in remote Jawoyn Aboriginal country in southwestern Arnhem Land, Australia. On the roof and pillars are hundreds of vivid interwoven shapes of humans, animals, fish and mythical figures, all painted in radiant red, white, orange and black pigments representing generations of artworks spanning thousands of years with mineral ochres, calcite, charcoal, hematite, and manganese oxide.

As societies advanced around the world, the transportation of materials became increasingly common. This was apparent in Ancient Greece and Egypt, where people imported paints from all over Europe and Asia to paint their temples and tombs (15).

Over 6000 years ago pigments included, sand, lime, and copper ore. These could be mixed together and heated to make a greenish blue pigment called Egyptian blue; a vibrant red was produced by mixing and roasting together hazardous mercury with sulfur; and white was made by sealing strips of lead in earthenware pots with vinegar and covering with manure. A vibrant blue pigment called ultramarine was created from the semi-precious gemstone, lapis lazuli (meaning blue stone in Latin).

The earliest paints used animal fat and saliva as a binding agent, and later, during the Middle Ages, artists used eggs to combine their pigments. However, by the 15th century, artists began using vegetable oils and dramatically transformed the art of painting.

Painting as described by Encyclopedia Britannica as, the expression of ideas and emotions, with the creation of certain aesthetic qualities, in a two-dimensional visual language. The elements of this language, its shapes, lines, colours, tones, and textures are used in various ways to produce sensations of volume, space, movement, and light on a flat surface.

The first recorded coating mill in America was reportedly established in Boston in 1700 by Thomas Child. A century and a half later, in 1867, D.R. Averill of Ohio patented the first prepared or “ready mixed” coatings in the United States and Sherwin-Williams sold the first pre-mixed wall coatings. Before that, people had to mix their own wall coating from powdered pigment.

These early coatings were primarily alkyd coatings with first variants being of the glycerol-diacid reaction, finding modification with oils derived from vegetable and fish oils providing the resins with solubility and flexibility (16). These oil-modified polyester resins were well suited for use as binders in coatings.

Synthetic pigments then were being discovered in the 19^th Century. From the early 1900’s the Industrial Revolution provided vast new markets for paints and coatings. Virtually every product created on an assembly line, from the Model T Ford to the latest-model television had extensive use of paints and coatings to beautify, protect and extend the life of the manufactured goods.

Many of today’s paints and coatings may go unnoticed by the consumer, but play immeasurably valuable roles in delivering high-quality foodstuffs, durable goods, housing, furniture and thousands of other products to market. Coatings are integral to the myriad of larger manufacturing and end-use industries.

The importance of coatings in this respect can be seen by research showing an average compound annual growth rate for the global coatings industry of 4.8% in revenue through to 2030 (14).

Harmful Materials

Various materials used in coatings throughout history have later been discovered as being harmful to either people or the environment.

Organic Solvents

The early alkyd coatings provide one of the earliest examples where environmental concerns were raised about organic solvents in the product formulations.

Heavy Metals

The second concern with these same oil-based coatings involved the pigments. The early versions of alkyd coatings used lead-base pigments and additives. White lead from Lead Carbonate (PbCO₃) or  lead hydroxide (Pb(OH)₂), was an ideal masking pigment with high opacity (17). Lead also enhanced other performance characteristics such as adhesion, water resistance, and weather-related flexibility. Lead has been shown to react with certain resin systems, linseed oils, or other oils to form metal soaps that are active corrosion inhibitors. Unfortunately, the toxic effects of lead presented a significant health risk for coating industry workers, professional painters and the general public, particularly children who could ingest the coating material after contact with weathered, flaking surfaces.

Although the U.S. Consumer Product Safety Commission has banned the manufacture of coatings containing lead since 1978, some countries still produce lead containing coatings and pigments. The health risk associated with lead-pigmented coatings still exists in structures that were painted up until the late 1980’s in Australia.

Chromium was also used in the form of zinc chromate in many primers for steel structures. Arsenic and cadmium have been used in coloured pigment manufacture mainly in greens and yellows. Each has its own toxicity to humans and presents environmental risks.

Biocides in Anti-fouling Coatings

In the early days of sailing ships, lime and later arsenic were used to coat ships hulls, until the modern chemical industry developed effective anti-fouling coatings that contained metallic compounds. These anti-foulings allow the controlled release of toxic compounds from the surface of the coating, making it very unattractive for barnacles, algae and other marine life to attach themselves to the hull of the ship. But various studies have shown that these compounds accumulate in the environment, killing sea life, harming the environment and possibly entering the food chain. One of the most effective anti-fouling coatings, developed in the 1960s, contain tributyltin (TBT) or similar organotin compounds, which have been proven to cause deformities in oysters and sex changes in whelks (18).

The coatings industry has a history of working toward sustainability over the past century by manipulating the chemistry of its products to better manage risks. Coating manufacturers started replacing lead pigments in some coatings, for example, before World War II, when safer alternatives became available.

Industry consensus standards limiting the use of lead pigments date back to the 1950s in the USA, when manufacturers led a voluntary effort to remove lead from house paints. Since then, other pigments such as the much safer titanium dioxide are mostly used.

Since the 1940s the coating industry has been working to reduce the VOCs and responded with innovative formulations that aimed to produce environmentally friendly, low-VOC, alkyd-based coating with the same or better performance than the traditional formulations.

In 2009, Proctor & Gamble Co. (Cincinnati, Ohio) and Cook Composites & Polymers (Sandusky, Ohio) were jointly awarded the Presidential Award for Green Chemistry by the U.S. EPA for their Chempol MPS product, an innovative alkyd resin technology that enables paint formulations with less than half the VOCs of traditional alkyds.

The harmful environmental effects of Tributyltin (TBT) compounds used in anti-fouling coatings on ships were recognized by the International Maritime Organisation (IMO) in 1989 and by 1999, IMO adopted a resolution calling for a global prohibition by 2008 (19).

Replacements for TBT have been based on metals such as cuprous oxide and co-biocides like zinc pyrithione. These have also proved to accumulate in the environment so coating manufacturers are developing new technologies to include low surface tension fouling release coatings, hydrophilic coatings and bio-based non-accumulating alternatives to cuprous oxide.

In 2011, the Sherwin-Williams Company (Cleveland, Ohio) was awarded the Presidential Green Chemistry Award for water-based acrylic alkyd coatings with low VOCs that can be made from recycled soda bottle plastic (polyethylene terephthalate or PET), acrylics, and soybean oil.

The coatings market continues to focus on new sources to develop environmentally friendly materials, introducing manufacturing processes and technologies that combine sustainability and performance.

Some examples of advancements that are innovating the present market are outlined below.

Green Chemistry and Alternative Formulations

Green chemistry refers to those items that involve the synthesis of raw materials or coatings from environmentally friendly processes rather than from more conventional sources such as crude oil. These processes may be using biodegradable raw materials, recycled materials, or have significantly decreased or zero VOCs due to an alternative manufacturing process.

One example is obtaining diluents for coil coatings from epoxidized fatty acids using renewable resources such as linseed oil and rapeseed oil (20). Another example is the development of sustainable polyurethane polymers from soybean oil that, when modified with silica, have low molecular weight and are free of VOC’s. Coatings formulated with this resin exhibit good performance and studies indicate that vegetable oil coatings based on soy monoglyceride-modified polyurethane and tetraethyl orthosilicate (SMG-PU-TEOS) have commercial application potential (21).

Further sustainability gains in coating manufacturing are being researched to develop coating formulations with lower VOC content, systems with lower film builds whilst still achieving suitable protection, protecting steel from hydrogen absorption, linings for bio-oils and new fuels. Smart coatings for absorbing hydrogen from steel, improving conductivity between metallic pigments, self-healing photo oxidation and inhibitor releasing nanotubes.

The manufacturing process is being optimised through specific reactions and VOC reduction to balance specific performance requirements of the coating such as adhesion-promoting additives with lower VOC content (22). Another example is the continued development of water-based protective and marine coatings, including anti-foulings, to reduce VOCs emissions (23).

In concrete protection, water borne epoxies and polyurethanes are now quite common, but they are still somewhat slow in gaining popularity in the steel protective coatings market, even though most manufacturers do make them. It is likely that further environmental regulation will continue to drive further development in this field, and it is almost certain that we will see more of these coatings in the not too distant future.

Also, powder coating technology has further developed, and powder coatings are starting to replace liquid applied coatings in many fabrication industries such as pipeline, windows, fencing and facades. Powder coatings provide all the components of a liquid applied coating except for the VOC’s and largely eliminate the need for solvent clean-up of application equipment and containers.

Nanotechnology

The introduction of nanotechnology has a significant role in the industry but is probably still in its infancy. Various manufacturers have used this technology to introduce ceramics or metals in the form of granules, free powder, or particles in various types of formulations. Some of the recent innovations that nanotechnology has enabled the formulators to develop include products that can better conduct electricity or exhibit UV protective or self-healing properties. Apart from these characteristics, they are also highly resistant to scratch, marring, wear, and corrosion. These advancements in technology look promising and the introduction of new products is expected to augment future advances in the coatings industry (24). For example, the use of graphene has been touted for use in coatings for over 15 years but only recently, after economically viable production methods and safe handling processes were discovered, the industry has started to develop formulations that will soon be widely available.

Another example where improving performance of environmentally friendly corrosion protection coatings is achieved, is by using polymeric micro and nano-containers loaded with 8-hydroxyquinoline and 2-methylbenzothiazole corrosion inhibitors via emulsion (from oil-in-water emulsions) by interfacial polyaddition (25).

Generally, change is brought about either by a company’s desire to innovate, new government regulations and/or changes in consumer demand.

The coatings industry has a history of adapting to all three drivers but a gap remains between the two stages of delivery of the finished product. Even though the manufacturer has tried their best to reduce embodied carbon and eliminate toxic compounds in the first stage, intended sustainability aims can be lost during the second stage being, coating application.

Sustainability gains can be achieved not only through chemistry and technological advances but also through field-based techniques to reduce waste, including;

• Use of application techniques that reduce overspray.
• Mixing of excessive quantities resulting in left over coating or waste.
• Applicators like to add thinners to their coating to make it easier to apply and there is a pattern of using 5% to 10% thus adding to the total VOC content.
• Coating application requires clean-up of equipment. This means using a solvent to wash the coating off brushes and rollers or flushing of spray equipment. This uses copious amounts of solvent and increases the release of VOC to the environment.

‘Paint back’ schemes are available in many jurisdictions and allow for reuse of waste coating as an alternative fuel source within manufacturing industries

The application industry should learn to understand and acknowledge the progress that manufacturers have made in reducing VOC and get involved to implement strategies that are initiated by sustainable formulation and manufacture and carry them through by adopting sustainable application methods.

Coatings matter since they provide many of the desirable properties people require for protection, decoration or identification of surfaces. However, in relation to sustainability, modern coatings provide;

• Heat reduction in urban heat islands – The urban heat island (UHI) effect is a common environmental problem occurring in metropolitan areas in which the air temperature is significantly higher than in suburban areas. The UHI effect also leads to a smoggy climate. Coating of concrete, steel and asphalt substrates with sunlight reflecting coatings can provide cool surfaces.
• Scavenger and photo catalyst products – nanoparticle engineered visible light responsive photocatalysts can be used in coatings to cause a photo catalytic reaction to either;

1. Suppress viruses such as COVID-19 which contact the painted surface with their ability to destroy pathogens using visible light (26); or,
2. Degrade pollutants which contact the painted surface such as Formaldehyde (HCHO).

• Lasting infrastructure – Notwithstanding the benefits a well-functioning infrastructure has to quality of life, coatings are used to extend the service life of the structure to which they are applied. Given suitable maintenance cycles, coatings can provide preservation of the structure enabling recycling or adaptive reuse at the end of service life of the protected structure. This leads to a reduced demand for raw materials.
• Fireproofing – protects structures for a period of time, from collapse during a fire event enabling safe egress of persons.
• Colour and mood – Colour is a powerful communication tool and can be used to signal action, influence mood, and even influence physiological reactions.
• Lasting transport – Coatings are used to preserve fuels in storage and reduce friction on ships hulls therefore making transport more fuel efficient.
• Anti bacterial for healthcare – antimicrobial coating additives provide lasting and effective protection against harmful bacteria, mould and fungi.
• Preserve foods – food can coatings are used to maintain the flavour, texture and appearance of canned foods by performing the dual role of protecting the filling from the metal and the metal from the filling.
• Road marking – The increased visibility provided by highly reflective coatings is used for road markings and indoor parking lots. Thus, coatings contribute to the safety of people and functioning of our transport infrastructure.

Steel and concrete make up the most abundant manmade materials on earth and coatings have a large role to play in making infrastructure durable.

As governments and industry make gains on embodied carbon and operational carbon, a growing focus will be keeping the carbon, embodied. This is part of the net zero strategy. Once carbon is embodied, we must aim to keep it embodied to prevent future release of carbon from that structure otherwise we must find another way to balance the release through capture of atmospheric carbon to gain a net zero balance. Examples would be sequestration and reforesting.

Project specifiers have a responsibility to select the most appropriate protective systems that provide optimum durability to our infrastructure. Particularly now the carbon footprint of maintenance interventions needs to be taken into account in an LCA, the advantages of durable protective systems and the consequent reduced number of maintenance panting interventions will lessen the overall environmental impact.

Reducing use of resources by painting less can be achieved through better selection and specification of coating systems. Asset owners are looking to adopt a whole of life approach to carbon reduction in building and infrastructure design, applying principles to identify cost effective low and, ultimately, net zero carbon designs (27). This is done through development of a lifecycle assessment (LCA). Additionally robust quality control programs during applicator works will provide the longest coating service life.

Effective Protection of Structures

A typical steel distribution pipeline at 610-mm API 5l Pipe Schedule 40 weighs about 254.9 kg/m. A 9-m run of this pipe would weigh close to 2.294 metric ton. If this steel pipe had to be replaced due to corrosion, the environmental cost is high. For every tonne of steel that is produced in a steel mill, approximately 1.4 tonnes of CO₂ is released into the atmosphere. Thus this 9 m pipe section has 3211 kg of embodied carbon (kg CO₂e).

To protect that same 9-m run of steel pipe with a standard three-coat, high-performance coating system would generate 3.27 kg of CO₂ emissions. Though 3211 kg CO₂e to replace the pipe versus 3.27 kg CO₂e to protect the pipe, is a dramatic difference, it is common for asset owners to allow degradation until replacement is required, rather than allocate resources to the maintenance that is required to extend the service life of the asset.

The same calculations can be provided to structural steel for example: A typical 610 Universal Beam contains 1273 kg CO₂e and coatings to protect the beam from corrosion contain only 3.52 kg CO₂e.

In addition to the CO2 produced from steel, the VOCs generated by the transportation of steel from the mill to the jobsite exceed those produced by high-performance industrial coatings that could be used to prevent asset replacement in the first place (28).

Table 2: Characteristics of common steel building elements.

Structural Steel 610 UB		API 5l Pipe Schedule 40
Length (m)	9	Length (m)	9
Weight (kg)	909	Weight (kg)	2294.1
Steel Embodied carbon (kg CO₂e)	1272.6	Steel Embodied carbon (kg CO₂e)	3211.74
Paint Embodied carbon (kg CO₂e)	3.52	Paint Embodied carbon (kg CO₂e)	3.27
External Surface Area (m2)	18.63	External Surface Area (m2)	17.28
Depth of Section (mm)	602	Outside diameter (mm)	610
Flange Width (mm)	228	Inside diameter (mm)	574.64
Flange Thickness (mm)	14.8	Wall Thickness (mm)	17.47
Web Thickness (mm)	10.6
Depth between Flanges (mm)	572

 

Example of Adaptive Reuse of Structures

A 2016 report titled Assessing the Carbon‐Saving Value of Retrofitting versus Demolition and New Construction at the United Nations Headquarters describes the sustainability values achieved by choosing to renovate rather than demolish in favour of new construction.

If the UN complex had been demolished and replaced with new construction of similar size, it would have taken between 35 to 70 years before the improved operating efficiencies of the new complex would have offset the initial outlays of carbon emissions associated with the demolition and new construction process (29)

These results indicate that the practice of demolishing existing structures and replacing them with new construction creates a significant initial carbon burden that is typically recovered over a very long carbon payback period. It is even possible, if one uses typical industry assumptions of a 50 to 60 year useful building life, that new construction will never recoup its initial carbon outlays when compared to a quality renovation (29).

In this context, building renovation can be considered a fundamental strategy to reduce near‐term carbon emissions as part of the national and global response to climate change (29).

¹Embodied carbon in paint calculated at 189.89 g CO₂e/m² for traditional ASNZS2312 PUR5 system. Values supplied from Hempel Footscray plant in Victoria, Australia.

Technological advances and innovations are not new to the coatings industry.  Although traditionally perhaps forced by regulation, materials suppliers have acknowledged the need to be proactive and demonstrated that they understand the need to keep up with changes in the market, including the drive to better sustainability and net zero. This does not only include the development of coating materials that are more sustainable in terms of their chemical formulation and method of production, but also coating systems that offer improved durability to reduce the number of maintenance interventions over the service life of our infrastructure.

Once the coating manufacturers have delivered their part of the puzzle, it is the responsibility of specifiers to select solutions that provide optimum durability and up to applicators to deliver the end product in the least harmful manner. On the path to 2050, embodied carbon can remain embodied by effectively preserving built assets with modern coating systems, enabling optimum durability and adaptive reuse in favour of demolition and new construction.

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4. Australian Government. Climate Change Bill 2022. s.l. : Parliament of Australia, July 2022.
5. Council, World Green Building. Bringing embodied carbon upfront. 2019.
6. Green Building Council Australia (GBCA) and Thinkstep-ANZ. Embodied Carbon & Embodied Energy in Australia’s Buildings. 2021.
7. Infrastructure Partnerships Australia. Decarbonising Infrastructure. 2022.
8. Iron and Steel Technology Roadmap. International Energy Agency. 2020.
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Justin Rigby is the Principal at Remedy Asset Protection (RemedyAP). He has extensive experience in the corrosion protection industry developed over 28 years and is a board member for the Australasian Concrete Repair and Remedial Building Association Limited (ACRA). Justin is an AMPP CIP and AMPP CUI lecturer, AMPP Certified Corrosion Technologist, Certified Protective Coatings Specialist, Icorr Level 3 inspector, DoT Level 2 Bridge Inspector and serves as Chairperson of the Australasian Corrosion Associations (ACA) Coatings Technical Groups. Justin also serves on various Standards committees in Australia and internationally. Justin has authored many papers for publication in prestigious journals and has presented at international and Australian conferences with regard to protection of concrete and steel using coatings technologies. He has a passion for project delivery and his focus is on introducing efficiencies and building team-based strategies with enhanced performance and cost benefits for Clients and their suppliers.