AURUNA® 311 Gold Cobalt Electrolyte

For the adhesive direct gold-plating of stainless steel and nickel

AURUNA® 311 is a strongly acidic alloy electrolyte for the adhesive direct gold-plating of stainless steel. It is preferably used for chromium-nickel steels, molybdenum steels and nickelbased alloys difficult to activate. Due to its strong activation effect, the electrolyte can be often successfully used as well for other passive materials difficult to plate.

The gold electrolyte is suitable for both strike gold layers and thick coatings in the decorative field. The coatings are ductile, low in pores and protect against corrosion. The alloy electrolyte can be used for rack and barrel operation as well as in reel-to-reel plating (e.g. spray and dip cells and brush).

AURUNA® 311 is also available as a cobalt-free special version.

Electrolyte characteristics

Electrolyte type

Strongly acidic

Metal content

2 (1.0 - 2.5) rsp. 4 (3.5 - 4.5) g/l Au

pH value

0.6 (0.1 - 0.8)

Operating temperature

Room temperature up to max. 40 °C

Current density range

2 - 6 A/dm²

Plating speed

0.04 - 0.15 µm/min

Anode material

Pt-Ti, MMO (type PLATINODE® 177)

Coating characteristics



Alloy composition

0.3 weight % Co
99.7 weight % Au

Colour of deposit

Deep yellow




165 HV (HV 0.015 (Vickers) approx. values)

Max. coating thickness

Approx. 10 µm

Density of the coating

Approx. 17.5 g/cm³


  • Hard gold electrolyte for the direct gold-plating of stainless steel
  • Very good activation effect – without halogenides
  • Low-pore, ductile and crack-free coatings
  • Suitable for strike gold layers as well as for thick coatings
  • Good throwing power
  • Available as a cobalt-free special version
  • The coatings are RoHS compliant
  • Suitable for rack, barrel and reel-to-reel plating


  • Household articles
  • Writing implements
  • Spectacle frames
  • Watches
  • Cutlery
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Questions about the product?

Markus Legeler

+49 7171 607 204

For inquiries and additional information
please contact

Umicore AG & Co. KG
Rodenbacher Chaussee 4
63457 Hanau-Wolfgang

Tel.: +49 (6181) 59 6005
Fax: +49 (6181) 59 2970

The information and statements contained herein are provided free of charge. They are believed to be accurate at the time of publication, but Umicore makes no warranty with respect thereto, including but not limited to any results to be obtained or the infringement of any proprietary rights. Use or application of such information or statements is at the user´s sole discretion, without any liability on the part of Umicore. Nothing herein shall be construed as a license or recommendation for use, which infringes upon any proprietary rights. All sales are subject to Umicore´s General Conditions of Sale and Delivery.