There are two important sources of zinc used in the galvanizing process:
- refined zinc is produced from a mix of both mined ores and recycled feedstocks. It is estimated that, on average, refined zinc contains about 10-15% of recycled feedstock
- galvanizers are also important purchasers of remelt zinc – that is scrap zinc from, for example, old zinc roofs that have been cleaned and remelted into ingot form
So, the refined zinc purchased by galvanizing plants contains a high proportion of recycled zinc and fully recycled zinc is often purchased to supplement use of refined zinc.
During the galvanizing process, any zinc that does not form a coating on the steel remains in the bath for further reuse. There is no loss of materials that may occur during spray application of other coating types.
Zinc ash (from surface oxidation of the galvanizing bath) and dross (a mix of zinc and iron that accumulates at the bottom of the galvanizing bath) are fully recovered. Any zinc metal within the crude ash is directly recycled for further use, often in the same galvanizing process.
The fine ash and dross are then sold to make zinc dust and compounds for a variety of applications such as rubber additives, cosmetics and electronic components.
Galvanized steel can be recycled easily with other steel scrap in the electric arc furnace (EAF) steel production process. Zinc volatilises early in the process and is collected in the EAF dust that is then recycled in specialist facilities and often returns to refined zinc production.
In 2006, the European steel industry (EU27) produced 1,290,750 tonnes of EAF dust, which contained 296,872 tonnes of zinc (i.e., 23%). 93% of this zinc (276,920 tonnes) was recycled. (source: Gesellschaft für Bergbau, Metallurgie, Rohstoff – und Umwelttechnik, Germany).
Steel products often have a very long useful life, e.g. many very old steel bridges are still in use. For that reason there is a shortage of scrap and the constant growth in infrastructure will have to be based on primary production of iron ore. The same applies to many other metals that are used in applications with a long useful life.