Precious metal recycling in electrolytic strip galvanising

Rethinking material cycles: Salzgitter and Umicore collaborate on the recycling of a rare precious metal.

Salzgitter AG and Umicore’s MDS (Metal Deposition Solutions) business unit have jointly established a process that enables the recovery of the rare precious metal iridium from anodes used in electrolytic strip galvanising. In doing so, the partners are contributing to resource conservation and the circular economy, as Salzgitter reports.
In electrolytic strip galvanising, so-called MMO anodes are used to apply a thin layer of zinc to steel strips as corrosion protection. Galvanised steel strips are used, for example, in automotive bodywork and the household appliances sector. The anodes, which are coated by Umicore MDS using a specialised process and manufactured to customer specifications, feature a precious-metal-based coating with iridium as its key component. These coatings must be renewed regularly. Until now, it has not been economically viable to recover existing coating residues prior to re-coating.
Iridium is one of the rarest non-radioactive metals and is regarded as a strategically important raw material for transformation processes, for example as electrode material for hydrogen electrolysers. Global annual production amounts to no more than 10,000 kg. This combination has recently led to a massive rise in the price of this precious metal on the world market.

Recovering iridium from coating residues and returning it to the material cycle

This makes it all the more interesting that new processes are making it possible to recover the iridium from coating residues and return it to the material cycle. “And this is precisely where our idea comes in; put simply, it involves recovering the iridium used on the anodes. We’re talking about up to one kilogramme a year,” says Dr Marc Debeaux, an expert in electroplating processes at Salzgitter Mannesmann Forschung GmbH.
In a joint project between the anode manufacturer Umicore Galvanotechnik GmbH, Salzgitter Flachstahl GmbH and Salzgitter Mannesmann Forschung GmbH, processes and interfaces were developed that enable the iridium to be returned to the material cycle in a cost-effective manner.
“Recycling iridium is a very complex and difficult process. At present, there are only a few providers on the market who specialise in this complex process. Here, we were able to act as intermediaries thanks to our many years of expertise in the field of precious metal recycling. Through joint trials and the development of internal processes, we have ultimately succeeded in integrating the process into day-to-day operations at Salzgitter Flachstahl GmbH,” explains Frank Friebel, Head of the Electrocatalytic Electrodes Division at Umicore’s MDS Business Unit.
The collaboration demonstrates how targeted recovery of valuable materials, even outside core processes, can yield sustainable benefits and provides impetus for a more broadly conceived circular economy.
Source: Salzgitter AG