• Precious metal recycling in continuous electro-galvanizing
• Rethinking materials cycles

Salzgitter AG and Umicore's business unit MDS (Metal Deposition Solutions) have jointly established a process that enables the recovery of the rare precious metal iridium from anodes used in the continuous electro-galvanizing process. In this way, the partners are contributing to resource conservation and the circular economy.

In electro-galvanizing, so-called MMO anodes are used to apply a thin layer of zinc to steel strips as corrosion protection. Galvanized steel strips find use, for example, in the automotive and the household appliance industry. The anodes, which are coated and customized by Umicore MDS in a special process, feature a precious metal coating containing iridium as the most important component. These coatings must be renewed regularly. So far, existing coating residues could not be recycled cost efficiently before recoating.

Iridium ranks as one of the rarest non-radioactive metals and is considered a strategically crucial raw material for transformation processes, for example as an electrode material for hydrogen electrolyzers. Its annual production volume worldwide only amounts up to 10,000 kg. This combination recently led to a massive upsurge in the price of the precious metal on the global market. Consequently, it is therefore even more relevant that new processes now make it possible to return iridium from coating residues to the material cycle. "And this is exactly where our idea comes in, which – to put it simply – is about recovering the iridium used in the anodes. Here, we are talking about up to one kilogram per year," says Dr. Marc Debeaux, expert for electroplating processes at Salzgitter Mannesmann Forschung GmbH.

In a joint project involving the anode manufacturer Umicore Galvanotechnik GmbH, Salzgitter Flachstahl GmbH and Salzgitter Mannesmann Forschung GmbH, processes and interfaces were created that allow iridium to be returned to the material cycle in a cost-efficient manner.

 
"Recycling iridium is very demanding and difficult. At present, there are only a few providers on the market who specialize in this complex process. Thanks to our many years of expertise in the field of precious metal recycling, we were able to act as an intermediary. By conducting joint trials and developing internal processes, we ultimately succeeded in integrating the process into everyday operations at Salzgitter Flachstahl GmbH," as Frank Friebel, Head of Electrocatalytic Electrodes at the Umicore business unit MDS explains.

 
The cooperation shows how sustainable effects can be achieved through the targeted recovery of valuable materials, also outside of core processes, and provides an impetus for a more broadly thought through circular economy.

Source:   Fuel Cells Works