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Advice on galvanizing

Hot dip galvanizing and respect for the environment

During the last few years, the signs of environmental degradation and the consequences of global phenomena caused by emissions, such as the greenhouse effect, the acidification of rains, eutrophication and the thinning of the ozone layer, have polarized the attention of the society on the theme of environmental conservation, now perceived as a primary necessity. An increased awareness of the need to respect the ecosystem in which we live, determines a growing attention to the impacts caused not only by industrial activities, but also by the products themselves during the entire period of their use, or also during the phases following the production.

This evolution, a veritable phenomenon of custom, is determining various effects at various levels on the procurement policy of Public Administrations, on the behavior of buyers in the market, on the programs of manufacturing companies. The European Commission has paid particular attention to these issues, with the intention of creating competitive advantages for companies that are more receptive and innovative. In this way, environmental performance has become key aspects of the value of industrial processes and products. In this complex framework, even the materials intended for construction, in the provisions of the law as well as in the free choices of consumers, are gradually subjected to criteria of preference no longer based only on cost and functional performance in their use. In addition to economic and performance considerations, for those who decide which materials and products to use, the greater or lesser environmental compatibility of their constituents also becomes discriminating, in a balance between pros and cons whose rules are dictated by the principles of sustainable development.

Zinc improves the environmental performance of steel

The preservation of environmental resources also involves the use of systems that prevent degradation to indispensable products, obtained with great material and energy expenditure. Anti-corrosion systems evidently increase the competitiveness of a product compared to others, with the positive influence determined by the increase in the service life of the works.  Hot dip galvanizing proves, even in this perspective, an excellent ally of steel. By ensuring long-lasting corrosion protection and without the need for maintenance interventions for decades, zinc avoids the environmental impacts associated with the actions of restoration and reconstruction of the compromised works. According to the criteria dictated by a modern technique of evaluation and comparison of environmental performances, the Life Cycle Assessment, in a comparison involving different building materials, the environmental loads connected with the production of a building work, must be distributed over the entire period of useful life of the product to be built. In this way, greater durability consists directly of a lighter environmental impact. Therefore, the increase in duration obtained with hot-dip galvanizing not only makes clear the difference in environmental performance between galvanized steel and steel protected with different processes, but also increases the competitiveness of steel constructions compared to alternative and usual construction solutions. use of cement. This is made possible by the characteristic properties of zinc, but also by the very low environmental load associated with the hot dip galvanizing operation, as we will see below in the paragraph relating to the application of Life Cycle Thinking.

A determining factor in achieving the progressive minimization of loads and impacts is the attention paid by operators in the hot dip galvanizing sector to the continuous improvement of the environmental performance of the production process. In fact, the galvanizing sector in Italy boasts a considerable number of ISO 14000 certified companies and a share of EMAS registrations which is much higher than the average of the other industrial sectors. Adherence to these certified environmental management systems leads to real progress, with an increased awareness of the importance of procedures for the environmental efficiency of production and compliance with laws and regulations. This virtuous process involves all levels of the company organization. This, as it should be, implies the full satisfaction of the laws and regulations in force on environmental matters by the companies. For the attention shown and the particular commitment to the dissemination of these systems, the Italian Galvanizing Association in 2006 received a recognition plaque from the Interministerial Committee for the Italian EMAS.

It is also worth remembering that the production techniques adopted today in the hot dip galvanizing departments correspond to national and community criteria, established for the prevention and control of pollution, universally known as BAT – Best Available Techniques, best available techniques. for the containment of emissions.

Galvanizing is the application of a zinc coating on steel. To evaluate the environmental value of the product and its behavior, it is therefore necessary to first analyze the effects of zinc on the environment and human health.

Zinc and the environment

Zinc is an essential metal, indispensable for the life of plants and animals, and obviously also for the life of man. It is an element naturally present in air, water and soil. All ecosystems benefit from its presence at different concentrations Zinc, since the dawn of life, has been “used” by nature with a specific role in various biological reactions. Consequently, there is an optimal zinc exposure range for every living organism. Plants and animals need zinc to grow and every organism is subject to seasonal fluctuations in its bio-availability. For this reason, evolution has created a mechanism called homeostasis, which allows you to regulate its contribution within certain limits. For this reason, bio-essential metals such as zinc, but also copper and iron do not accumulate inside the body, but are balanced with each other. In case of deficiency they accumulate and any excesses are expelled We are used to negatively consider the effects of many substances used by man and by industrial activities. In most cases, we hear about the need to limit their release to the environment to a minimum This is true for all synthetic substances. For elements present in nature regardless of human action and, in particular for bio-essential ones, this statement is not necessarily true.    

The International Chemical Safety Program (IPCS), a world forum organized by WHO, the World Health Organization and the UN, has faced a discussion in order to establish environmental health criteria for zinc. The conclusion is that zinc is a necessary element for the environment, so there is a possibility of both deficiency and excess. For these reasons it is important that the regulatory criteria are not set at such low levels as to bring zinc into the area of deficiency.  The possibility of introducing zinc into the environment from hot-dip galvanizing does not involve concerns for the soils on which the galvanized products are installed. In fact, zinc corrosion products for applications such as galvanizing do not reach concentrations such as to cause concern, given the reduced speed with which dissolution occurs. After all, this is the greatest strength of the protection obtained using zinc.

A research carried out by the University of Ancona, the results of which were published in the scientific journal Chemistry and Ecology in 2002, showed that even for large structures, such as high voltage pylons, in the surrounding soil, already at a distance less than 1m, there is no variation in the zinc concentration compared to natural values. The structures are installed in urban-agricultural and urban-marine areas in the territory of Parma and Ancona and after about 30 years from their installation they retain a quantity of zinc on the surface that is still up to standard. The analysis sites were chosen so as to be representative of the average composition of the Italian soil.

It is therefore established that there is no risk for the soils This was also recognized by a risk assessment study – Zinc Risk Assessment of the European Union, forthcoming. The Competent Authorities of the EU Member States have also recently (December 2006) established that with regard to the control of the release of zinc in the various environmental compartments (soil, water and sediments), it is not necessary to regulate processing industry products, including hot-dip galvanized coatings. 

Zinc and human health

Zinc plays an essential role in human metabolism. For example, zinc is vital for the proper functioning of more than 200 enzymes, for the stability of DNA and for the expression of genes, as well as for the transmission of nerve signals.  The human body contains 2-3g of zinc (and, for example, 7g of iron) which is found all over the body, with the highest levels in the muscles, liver, kidneys, bones and prostate. The recommended daily intake is 12mg / day for adult women and 15mg / day for adult men. The daily intake depends on gender, age and general health. Infants, children, adolescents, pregnant women and the elderly need more zinc. Certain groups of the population, especially in the most depressed areas, are subject to the serious risk of not having a sufficient supply of zinc from their diet. The consequences of insufficient intake are skin diseases, drowsiness, reduced sensitivity of taste and smell and, even, reduced fertility and weakening of the immune system.

In addition, on the opposite side, recent studies carried out by the Competent Authorities of the Member States of the European Union on behalf of the Commission, have reiterated that the current use of zinc in all human activities does not cause exposure to risk for human health.

Zinc and steel are totally recyclable On the other hand, zinc also has the advantage of being a recyclable material. Today, around 30% of the zinc used is obtained from recycling. It is difficult to be more precise with this figure, due to the fact that the products obtained from zinc have a very long average life of use. In addition to hot and electrolytic galvanizing, in fact, this material is also used for the production of brass and die-castings. The protection of a galvanized steel product often lasts longer than the useful life of the product itself and the residual zinc can be made available for recycling even after a period of 100 years. The steel that galvanization protects so effectively, at the end of its life, that is, after the use phase, is just as recyclable. Being simple chemical elements, zinc and iron can be recycled without any loss of physical characteristics or chemical properties.   

The life cycle perspective applied to hot dip galvanizing

Concepts such as recyclability, the assessment of impacts and loads, of the environmental risk associated with human activities from the beginning of the production chain to the final destination of the product, are already present in current regulations. Environmental policies are being refined within schemes that require an assessment of environmental performance from the perspective of the entire life cycle. A new frontier of eco-sustainability marks the transition to an integrated management of environmental protection, so that the evaluation of any phase of the product’s life is not neglected, starting with the extraction of raw materials, passing through production and use, until recovery or disposal.  In other words, this growing attention to environmental issues necessarily involves a new way of thinking about industrial production and the supply of goods and services. This is what is now called Life Cycle Thinking.  Alongside this, note the importance of community policies for sustainable development in the context of IPP – Integrated Product Policy, and some inspiring principles of green procurement – green procurement, for which public administrations and large companies private individuals should favor the most eco-efficient products in the purchase. Perché tutti questi processi possano risultare in azioni efficaci occorre uno strumento quantitativo che permetta di stabilire con oggettività l’ efficienza ambientale di un sistema produttivo, di un servizio o di un’ applicazione.

The operational means of Life Cycle Thinking is the LCA analysis – Life Cycle Assessment, which addresses this determination by following step by step the creation of the usable good, starting from the extraction of raw materials, through the loads connected to all the transformation activities and its useful life, up to the return to the land or to the production chain, in the form of recycled waste.

The LCA of hot dip galvanizing

In 2005, hot dip galvanizing was the subject of a pan European LCA study carried out on a sample of 46 production plants in European countries whose National Associations of galvanizers (and among them the Italian Galvanizing Association) belong to the EGGA (European Association of hot dip galvanizers), with a total production of 937,000 tons out of a total of almost six million. In fig. 12.3, the number of plants involved for each European country.

The data collected made it possible to establish a life cycle inventory, or a model that allows us to reconstruct the flow of energy and materials that characterizes hot dip galvanizing, through the set of transformation and transport processes involved along the entire production chain. . This constitutes a model of the real system that describes and quantifies the environmental loads of each single phase, as well as of the process as a whole.

A comparative study

An example of the possibilities offered by the LCA analysis to support designers in choosing the most environmentally friendly protection system, is the study carried out by the Technical University of Berlin, for the comparison of the eco-efficiency between two different steel parking structures, one of which is hot-dip galvanized and the other simply painted. The comparative analysis was carried out on the basis of the results of the pan-European EGGA study.

The hot-dip galvanized structure complies with the requirements of the UNI EN ISO 1461 standard with a zinc thickness of 100μm, supposedly free from the need for maintenance given the corrosion class C3 environment (according to ISO 9223 and UNI EN ISO 14713). The painted structure complies with the specifications of the EN ISO 12944-5 standard. The painting was applied after Sa 2 ½ grade sandblasting for the surface preparation of the steel; the coating is epoxy in nature with a thickness of 240μm. Painting maintenance is planned after 20 and 40 years from the first application.  

The functional unit chosen, the basis for the comparative LCA analysis, consists of the protection of 1m2 of surface for a duration of 60 years of the structure. The steel section used in the construction is of average size with a characteristic surface / weight ratio of 20m2 / ton. An interesting result, which the study highlighted, is that the hot dip galvanizing of the 500 tons of steel used in the construction of the hot dip galvanized parking lot results in a lower emission of 57 tons of CO2 with 60 years of useful life. The data do not change significantly for shorter durations, i.e. for different observation times. In fig. 12.7 there is a simple comparison between results that can be obtained after different time intervals. It is noted how the performances are always better for hot dip galvanizing in the case of the indices relating to energy consumption and greenhouse effect. The other indices also align with this trend after the maintenance required for the painting conventionally placed 20 years after the installation of the product. It should be noted that this duration of two decades for a coating is out of the ordinary and constitutes a favorable data in comparison with galvanizing.

Product Category Rules of galvanizing and other anticorrosive treatments

In January 2006, the PCR (Procuct Category Rules) for the corrosion protection systems of steel were published by the Swedish Environmental Management Council, the Swedish body that implemented the environmental product certification system known as EPD – Environmental Product Declaration. PCRs (formerly referred to as PSRs) provide specific product requirements to be considered when drafting an environmental statement. The spirit is to make the different systems that can be adopted comparable. For this reason, the document containing the PCR, also dictates the rules for carrying out the LCA study at the basis of the declarations. In this way we obtain a standardization of certified reliability of the comparison of the environmental performances of galvanizing, painting, stainless steel, corten steel. The PCR, in defining the functional units, that is the reference units for quantifying the efficiency in terms of significant environmental performance for the purposes of a life cycle analysis, requires that the duration of the protection be clearly indicated, dividing its entirety the totality of environmental loads. This constitutes a reference of extraordinary importance Through these tools, the fundamental property of galvanizing is highlighted, which is represented by its remarkable durability, which gives the galvanized product a new perspective of environmental competitiveness as well as economic and technical-functional.  

The PCR document makes it possible to compare and contrast LCA and EPD studies both between zinc plating companies and companies offering competing systems and between companies operating in the same galvanizing sector.

The EPD environmental certification of galvanizing

The companies that provide the hot dip galvanizing service, on the basis of the LCA studies conducted, following the criteria established with the PCR document, can offer their customers a declaration verified by an accredited certification body and registered with the EPD mark. With the environmental product declaration EPD, they publicly expose the environmental performance of their production. This declaration represents a reliable dissemination tool, which will have an increasingly important role in the context of international regulations and in the implementation of sustainable purchasing policies by public administrations and private companies of a certain size.