Lack of attention to optimal corrosion protection can leave a damaging legacy of repeated maintenance costs, which can significantly increase the life cycle carbon footprint of buildings and infrastructure. The repeated painting of steel structures is an environmental and economic burden that can be avoided.
In addition to the life cycle benefits of galvanizing steel, the efficient use of resources is key to the circular economy. The steel industry has developed high-strength and advanced high-strength steel grades for many applications. These grades contribute to the light-weighting of applications, from wind turbines to construction panels and automobiles, as less steel is needed to provide the same strength and functionality. By providing maximum levels of corrosion protection, galvanizing allows for more efficient design solutions to be used.
Galvanizing’s ability to optimise the durability of steel structures and components has important environmental, economic and social advantages. There are high economic and environmental costs associated with the repeated maintenance painting of steel structures. These burdens can be significantly reduced by an initial investment in long-term protection. The long-term durability provided by galvanizing is achieved at relatively low environmental burden in terms of energy and other globally relevant impacts, especially when compared to the energy value of the steel it is protecting. Whether it is by reducing maintenance operations or avoiding the premature replacement of steel products, galvanizing will reduce the embodied carbon of construction.
A study by the Environmental Technology Systems Department of the Institute for Environmental Protection Technology at the Technical University of Berlin involved a comparison between a paint coating (EN ISO 12944) and hot dip galvanizing (EN ISO 1461) for a steel car park in a life cycle assessment (LCA).
The functional unit – the reference quantity for the comparison was that the two systems had to provide corrosion prevention for a steel structure which was to be used for 60 years, and which was applied to a 500 tonne steel structure such as a multi-storey car park with a steel area amounting to 20 m²/t. It was assumed that the structure was externally exposed to a medium level of corrosion (corrosion category C3 from ISO 9223).
The hot dip galvanizing system is a ‘one-off’ corrosion prevention treatment by immersion in molten zinc. With a galvanized coating thickness for this example of 100 μm and an average corrosion rate for category C3 of 1 μm/year, the calculated durability far exceeds the required 60 years. To guarantee corrosion prevention for 60 years using the paint coating system, the components are first abrasion-blasted to remove any rust. Then they are painted in the works with a three-coat application with a total coating thickness of 240 μm. On-site maintenance operations are then needed after 20 and 40 years.
Long service life and freedom from maintenance, the well known advantages of hot dip galvanizing, result in lower consumption of resources and less pollution throughout its service life. In this example, as shown in the table below, a saving of 57 tonnes of CO2 was achieved over the 60 year life of the car park.
For further information on this LCA comparison, visit:
www.galvanizing.ie/circular-economy/reduce-carbon-footprint
The Eiffel Tower – A Maintenance Legacy
When Gustave Eiffel constructed his famous tower in 1889 for the International Exposition and centennial celebrations of the French Revolution, it was envisaged to be a temporary structure. Little did he know that it would still stand as the much-loved landmark of Paris over 130 years later.
But this longevity has come at a price. The Eiffel Tower’s ironwork has been repainted 19 times and a maintenance painting cycle takes 18 months at a cost of €4 million. The repainting costs are estimated to be ~14% of the current construction cost of the tower.
The upper sections of the Eiffel Tower are painted every 5 years and the lower sections every 10 years- Each repaint applies 60 tonnes of paint and 15-20 tonnes of paint are eroded between each repaint
- Removal of all existing paint before repainting cannot be done without lengthy closures
- Each repaint adds ~40 tonnes of paint – making it 700 tonnes heavier than its intended design
- 25 painters, wearing 1,500 sets of work gear and 1,000 pairs of leather gloves
- Relying on 50 km of safety lines and 800 m2 of safety nets, 1,500 paint brushes and 5,000 abrasive discs
- €4 million for most recent repaint
It is the costs in resources, risks for worker safety and the structural consequences of this repeated painting that goes unseen by the millions of tourists that visit this iconic structure. With ~40 tonnes of residual paint added to the structure at every repaint, the structural consequences of this additional mass will eventually have to be solved. In recent painting programmes, it has been necessary to start to remove all 19 previous paint layers from certain areas of the tower to maintain its structural integrity.
A lesson for today’s structures which are far too often built without durability and avoidance of maintenance in mind.
The result of international collaboration, “Galvanized Steel and Sustainable Construction: Solutions for a Circular Economy” draws on academic research and examples of best practice from across Europe. It explains clearly how galvanized steel can help the construction sector adapt to a net zero future.
Galvanized steel can provide innovative solutions that optimise durability and facilitate circularity of steel structures and components. These solutions can be easily implemented using this well-established and simple method of protecting steel.
Visit our website
www.galvanizing.ie/circular-economy
to download or request the publication