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Is hot-dip galvanizing sustainable?

Is hot-dip galvanizing sustainable?

July 2014

Sustainable development is the social, economic and environmental commitment to growth and development that meets present needs, without compromising the ability of future generations to meet their own needs. As social pressure to build a sustainable environment continues to mount, designers are increasingly invested and analytical when selecting materials.

Hot-dip galvanizing can contribute positively to sustainable development initiatives due to its durability without any maintenance required, its being 100% recyclable, its minimal environmental impact, and its savings for future generations. This section includes information about the low environmental impact of hot-dip galvanized steel on the basis of the life cycle assessment (LCA) - an objective and thorough study of a green product or material. The LCA measures the energy consumption and emissions created by operations (zinc and steel mines) at the end of the galvanized product's life.

Galvanizing diagram

When looking at the low environmental impact of galvanized steel and its superior economic advantages (low cost life cycle), it is easy to see that hot galvanized steel is really a smart and sustainable building material .

Environmental benefits of hot-dip galvanizing

The hot-dip galvanizing coating is 98% made up of zinc, a natural and healthy metal. Zinc occurs naturally in air, water and soil and is the 27th most abundant element in the earth's crust. Over 5.8 million tons of zinc are naturally cycled in the environment by the plant and animal life, precipitation, and other natural activities. Zinc is essential to life - from man to the smallest microorganisms. Therefore, the use of hot-dip galvanized steel is not harmful to the environment, since zinc is already naturally present.

Besides being natural, zinc, as steel, is infinitely recyclable without loss of physical or chemical properties. About 30% of the world's zinc supply comes from recycled sources every year, and more would be recycled if it were available. Also, steel is the most recycled material in the world, with nearly 100% of structural steel coming from recycling, which makes galvanized steel an infinitely renewable material.

Steel zinc recycle loop

A life cycle assessment (LCA) is an objective measurement of a product's environmental impact. Often called a "cradle-to-grave" study, a LCA quantifies the environmental impact of a process or product, from raw material acquisition, energy inputs and emissions during production, and the use and management of recovery/disposal at end of life. LCAs began to gain favor with the specifiers community by being a way to measure a product's sustainability.

In 2008, the "International Zinc Association (IZA)" hired international experts LCA Five Winds PE International Partners to conduct a life cycle inventory (LCI) and life cycle assessment (LCA) for hot-dip galvanized steel. Using data from sources around the world in terms of energy consumption and air/fluid/solid emissions measured during the production of zinc and during the actual galvanizing process, combined with data collected from the similar survey by the steel industry, a LCA for hot-dip galvanized steel has been compiled. This study has provided a basic understanding of the industry's impact today, which the AGA has committed to improving in the future.

Hot-dip galvanizing is unique, since all material and energy inputs and emissions are isolated at the production phase. Hot-dip galvanizing does not require any maintenance during the practical lifetime of most structures, i.e. 75 years or more. This means no transportation of labour on the repair site, no energy, no emissions such as from sand blasting or paint dust during removal, and no material required after the initial production and installation of hot-dip galvanized steel.

Economic cost of hot-dip galvanizing

The second principle of sustainable economic development is often overshadowed by the importance of environmental impact. However, in addition to the construction of structures that are environmentally friendly, true sustainability for these structures must also be economically responsible for future generations.

Hot-dip galvanized steel can provide savings both initially and throughout the life of a project, freeing money for new construction, rather than costly maintenance. It has long been a perception by the specifiers community that hot-dip galvanized steel is prohibitively expensive initially. However, due to the steady improvement of processes, hot-dip galvanized steel is not only competitive, but often less expensive initially than other corrosion protection systems. In addition, due to short lead times and fast installation, the use of hot-dip galvanized steel allows for even more savings during construction.

Although the initial cost is significant, analysis of costs throughout the life of the project provides a more complete picture of costs for future generations. The life cycle cost (LCC) takes into account not only the initial cost, but also the direct maintenance costs

Since hot-galvanized steel offers decades of protection against corrosion with no maintenance required, the initial cost is often the final cost of the life cycle. Evaluating the LCC can be arduous, so to facilitate analysis, the AGM developed the Life Cycle Cost Calculator. The online calculator allows users to enter a project's parameters and compare the initial costs and life cycle of hot-dip galvanizing with over 30 other of corrosion protection systems, based on published costs.

Source: AGA - American Galvanizers Association

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