Taking the lead in changing the way age-old processes are done can be a daunting and dangerous experience. It can also be financially rewarding and satisfying. What the news business might call “leading or bleeding.” Whether new technology—looking at you, AI—or new processes, finding answers to questions that seem to already be answered is the way science is supposed to work.
Take the basic components of construction, both buildings and infrastructure. Concrete production is going through various stages of experimentation to reduce the greater part of its CO2 emissions. Competing processes all show some advantages so narrowing them down to the best one or two will take time and effort. The result, however, will be judged through comparisons of CO2 generation and capture are done over time.
Steel, the world’s most important metallic construction material, is favored because of its mechanical properties, availability, and relative affordability, making it a staple in many building and infrastructure projects. But steel has weaknesses as well as strengths. Left untreated, steel is susceptible to oxidation and subsequent deterioration, with tell-tale signs of damage such as cracking and rusting especially prevalent in moisture-rich environments.
Protection against corrosion can lengthen the service life of steel products and ensure safety requirements by averting material failure. In 1742, a chemist presented a paper to the French Royal Academy in which he described how a zinc coating could be obtained on iron by dipping it in molten zinc. Thus began the industry known as galvanizing. For centuries, zinc coating iron and steel has been the standard for weather protecting these important construction materials.
Using zinc to galvanize steel is an effective and economical way to improve the performance of steel and ensure its longevity. The coating protects steel against corrosion and deterioration, which the IZA (Intl. Zinc Assn.) estimates can cost the economies of industrialized countries at least 4% of gross domestic product every year. That adds up to $2.2 trillion lost per year worldwide, with $423 billion lost in the United States alone.
About a third of that is avoidable corrosion, meaning that if the proper precautions are taken, the United States could save nearly $150 billion every year. Aside from the cost that corrosion incurs, and the time and energy required to maintain structures that cannot withstand their environment, there are safety hazards to consider. Bridges, pipelines, buildings, and other materials that are built from non-galvanized steel require a great deal of extra maintenance to prevent collapse from corroded metals.
Now, experimentation is underway for a similar-but-different approach, one that combines steel protection with waste recycling to benefit the environment. Recycled aluminum alloy coatings (ALCOAT) with chemically tailored electrochemical potential for safe protection of steel structures will recycle aluminum destined for landfill to create an alternative to zinc for the galvanization of steel products.
According to the European branch of the RMIT (Royal Melbourne Institute of Technology), scrap aluminum is widely available but is usually contaminated with iron and magnesium, making it brittle and unusable for many applications. Hence, it is often either discarded or used for lower-level purposes such as pellets. However, this material can produce a good coating for steel as the contaminants it contains help stop oxide from forming.
This strategy of reusing existing scrap materials is one of the advantages of the project. While zinc continues to be widely used to protect steel from corrosion and is highly effective, it is also difficult to recycle. ALCOAT will address this as a sustainability issue rather than a performance problem, RMIT claims. Using existing scrap materials will also negate the energy-intensive process of mining and processing virgin zinc for this purpose and the associated negative costs to the environment.
RMIT is leading the computational modelling to integrate numerous multi-scale approaches based on material modelling and molecular chemistry, the latter led by the ICN2 (Institut Català de Nanociència i Nanotecnologia) in Barcelona.
The aluminum alloy coatings are expected to have several advantages, such as a lower corrosion rate and a reduced risk of hydrogen embrittlement, which can occur with zinc coatings of high strength steels. They will also be lighter, thinner, and more sustainable given the reduction in the quantity of primary raw materials required, thereby also boosting efforts in the circular economy.
It is expected that ALCOAT will contribute to improvements in the safety of steel constructions and provide a powerful tool to enhance other metal coating systems for material protection. The ALCOAT coatings will initially be used in the protection of wind towers, ships, and other structures exposed to sea water and atmosphere as well as steel sheet products for automotive, building, and home appliance industries.
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