PROJECT DESCRIPTION
BACKGROUND
Zinc mines are rapidly depleting throughout the world. In the EU, the situation is even more problematic, as almost all Member States (with the exception of Ireland) rely on imports. At the same time, zinc waste represents a real environmental problem due to its progressive loss in the hot zinc-coating process, where molten zinc alloys are used to galvanise steel wire in order to improve its resistance to corrosion. In this galvanising process, up to 60% of the applied zinc turns to ashes and solid residues. As a result, large amounts of zinc are required. Overall, it has been estimated that 30 million tonnes of galvanised steel wire are produced in Europe, of which 4.5 million tonnes are produced in Italy, consuming more than 1 070 000 tonnes and 160 000 tonnes respectively.
The recycling or reuse of zinc chips has economic as well as environmental benefits. However, recycling is rather difficult to pursue because the hot zinc reacts with the underlying steel, forming intermetallic compounds that are difficult to recover. As a result, the most feasible process to address the problem is the reuse of the metal.
OBJECTIVES
The main objective of the LIFE M&M Man and Metal project was to develop an innovative business model for obtaining an eco-compatible metal wire in which the traditional hot-dip galvanising treatment is replaced by a controlled application of lighter and thinner protective metals (containing a high percentage of aluminium, better known as quasi-alloys). The end result would be durable and fully recyclable products with maximum corrosion resistance. The aim was to find alternatives to zinc, thereby increasing the useful life of the product and reducing the amount of protective coating. It would have a positive environmental impact.
RESULTS
The LIFE M&M Man and Metal project demonstrated the feasibility of a new process for the production of eco-compatible metal wire that replaces the conventional hot-dip galvanising treatment with a controlled treatment of different protective metals, such as the aluminium alloy. First, the most suitable methods of deposition for the alloys and pseudo-alloys for protective steel coating were selected and the system for the recovery of over-sprayed powders was defined. The project used a thermal process and a new spray system to identify recycled metals for the production of these alloys and psuedo-alloys.
The next step was to design a micro-peening prototype, which entailed an adaptation of the pilot plant that was erected in the factory of Metallurgica Abruzzese for the project ‘Ultra Crash Treatment’ (LIFE09 ENV/IT/000174). The demonstrative line used a range of process parameters in order to ensure the quality and cost-effectiveness of the wire rod. Tests showed that the innovative coating has a corrosion resistance similar to or higher than that of hot dip galvanised steel.
A spray system was also created and tested, with the production of electro-welded nets started. The properties of all the wires and nets were then assessed, including their metallography, thickness, tensile strength, micro-hardness and corrosion potential. Samples were also tested in the field by selected customers in the agricultural, livestock, and fish farming sectors, with good results.
The Life Cycle Assessment confirmed the benefits of the project:
- 87% reduction in the use of zinc (or by 66 tonnes/year) after the industrialisation of the process;
- Increased use of recycled material of zinc and aluminium (by 26 tonnes/year) after the industrialisation of the process;
- 22% reduction of embodied energy and of CO2 production compared to traditional galvanised wire; and
- Increased durability, aesthetical appearance, and corrosion resistance (+150%).
The beneficiary has integrated the prototype machinery in its production line in order to take advantage of the cost benefits.
Further information on the project can be found in the project's After-LIFE Communication Plan (see "Read more" section).
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