AURUNA® 313 Gold Iron Electrolyte

Cobalt-Free Solution for Direct Gold Plating on Stainless Steel

AURUNA® 313 is a highly effective, strongly acidic gold plating solution that allows direct gold plating on stainless steel with excellent adhesion. The product is particularly suitable for Cr–Ni steels, molybdenum-containing steels and nickel-based alloys that are difficult to activate. Thanks to its strong activation effect, AURUNA® 313 can also be effectively applied to other passive materials that are difficult to electroplate. Where necessary, the activation process can be supported by specialized pre-treatment steps.

The process requires no base metal interlayer while avoiding any degradation of corrosion resistance. The solution is free of chlorides and fluorides, suitable for both technical and decorative applications. The solution system has a wide operating range, compatible with rack, barrel and reel-to-reel plating lines.

The coating from AURUNA® 313 is crack-free, ductile and low-porous. Bright plating is possible up to a thickness of 0.5 µm. The plating speed is sufficiently high to achieve the required thickness directly from the solution in many cases, ensuring economic efficiency. The coating maintains stable brightness over time.

Solution Properties

• Solution type: Strongly acidic
• Metal content: 2 (1–3) g/l Au; 0.5 (0.3–1.0) g/l Fe
• pH value: 0.9 (0.8–1.0)
• Operating temperature: Room temperature up to max. 30 °C
• Current density range: 4 (0.5–8.0) A/dm²
• Plating speed: Approx. 0.07 μm/min at 4 A/dm²
• Deposition rate: Approx. 3.4 mg/Amin at 4 A/dm²

Coating Properties

• Coating: Gold-iron
• Purity: 99.5% Au; 0.5% Fe
• Coating color: Deep yellow gold
• Coating hardness: Approx. 165 HV
• Maximum coating thickness: 0.5 μm
• Coating density: Approx. 19 g/cm³

Advantages

• High activation efficiency – halide-free
• Direct gold plating on stainless steel with excellent adhesion
• Crack-free, ductile, low-porous coating
• High corrosion resistance
• Wide operating range
• Suitable for technical and decorative applications
• Compatible with rack, barrel and reel-to-reel plating

Applications

• Watches
• Household items
• Writing instruments
• Eyeglass frames
• Fashion jewelry
• Cutlery
• Electrical contacts
• Stainless steel contacts
• Stainless steel springs