Umicore brings gold-silver electrolyte for cost-efficient coatings

In response to the rise in gold prices, Umicore MDS has developed Auruna 5750, a gold-silver electrolyte that enables 12-carat intermediate and final layers. These layers contain half of each precious metal. Due to the different densities of the two precious metals, around 60% of the precious metal costs can be saved compared to pure gold layers. Overall, the gold price is showing a strong upward trend. The uncertainties in the global economy and geopolitical tensions make gold an attractive safe haven for investors at present and will probably remain so in the future. Gold has a high density of around 19.3 g/cm³, which is more than all possible alloy partners. This means that an alloy requires less mass to fill the same volume. With Auruna 5750, the savings effect is clearly evident due to the 50 % silver content and enables a further cost saving of around 10 %.

Umicore Auruna 5750 hard gold coating

Auruna 5750 is not only convincing due to its cost efficiency. The deposited layers also impress with their ductility, which is atypical for hard gold (220 HV / hardness according to Vickers), and their seemingly contradictory, extraordinary abrasion resistance. This is confirmed in the Bosch-Weinmann test, in which very low abrasion and layer removal values are achieved compared to conventional gold alloys due to the high degree of hardness and the lubricating properties of the silver. Compared to gold-iron or gold-cobalt alloys, which also lead to a gold-yellow deposition, the abrasion values for Auruna 5750 are almost halved. When comparing possible alloys, the particularly low abrasion values of Auruna 5750 become apparent. Auruna 5750 is not only the first choice for cost-optimized gold plating as an elegant pastel gold finish. It is also suitable for protective and color-preserving intermediate layers, for example for jewelry or plug contacts where a more intensive gold tint is desired. The coatings are particularly flexible and resistant due to the high silver content. Even with thicker layers, the shine is completely retained. Auruna 5750 is not only the first choice as an elegant pastel gold final layer, but can also be used for intermediate layers that retain the color tone.

Environmentally friendly electrolyte with easy handling

Another advantage of Auruna 5750 is its low environmental impact. The electrolyte does not contain any toxic heavy metals and therefore meets the strict technical standards of the RoHS directive. Nevertheless, the alloy provides reliable protection against corrosion. The uniform and stable coating also extends the service life of the coated objects. The electrolyte is easy to handle and insensitive to metallic impurities - regardless of whether Auruna 5750 is used for rack or barrel goods. Due to the wide range of possible applications, different coating thicknesses are required. Care has therefore been taken to ensure that crack-free deposition is possible up to a thickness of 10 µm. If very thin layers are required, an even more cost-effective variant with a low gold content can be used, resulting in additional savings.

Cost-efficient gold coating for electroplating

"With Auruna 5750, we are once again setting new standards in electroplating," says Martin Stegmaier confidently. The Head of Decorative Applications is delighted to be able to offer his customers this cost-efficient gold-silver electrolyte so quickly and explains: "The rapid development was made possible by our decades of experience with related alloys from electroforming. This established basis makes Auruna 5750, with its truly outstanding properties, a future-proof choice for the electroforming industry." With Auruna 5750, an innovative gold-silver electrolyte is available as an economical solution for gold plating that meets the highest demands. However, Thilo Kuhn, Head of Sales and Marketing, knows that despite its outstanding properties, the electrolyte may have to overcome internal hurdles with producers. He explains: "In some cases, lengthy qualification processes are necessary in order to convert production lines. That's why we offer an uncomplicated prototype coating together with a profitability calculation. In this way, we can dispel any concerns about whether a changeover is actually worthwhile."