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Gold Electroplating

From the ancient Mycenaeans who created it to Heinrich Schliemann’s rediscovery of the famous “Agamemnon’s Mask” some 3500 years later Gold has captured the imagination and desires of rich and poor alike across the ages.

In addition to the metal’s well-known aesthetic properties and monetary store of value, Gold also brings many desirable and useful attributes to industrial and scientific products.

As with plating other materials, Gold Electroplating is the deposition of a thin layer of Gold onto the surface of another object. Although more expensive than many other plating materials, the many superior benefits of Gold often outweigh the added expense.

AOTCO plates all typical gold types (Type I-III, 99.7%, 99%, and 99.9% gold) for both hard AND soft gold. Hard and soft gold can be differentiated by the following:

Soft Gold

Soft Gold is the go-to option when requiring one or more of the following applications or properties:

  • High Gold Purity

  • High Corrosion Resistance

  • Solderability

  • Wire Bonding

Soft Gold has fewer metal impurities compared to Hard Gold. This provides higher corrosion resistance while optimizing the deposit to eliminate high temperature oxidation.

Hard Gold

In contrast, Hard Gold is the better choice when a plated part is subjected to mechanical forces. The impurities strengthen the hardness of the deposit, but as a result this slightly reduces solderability/ wire bonding/ high temp oxidation resistance in comparison to Soft Gold.


  • Corrosion protection

  • High tarnish / oxidation resistance

  • High electrical conductivity

  • High thermal conductivity

  • Infrared reflectivity

  • Improved wear resistance

  • Low contact resistance

  • Excellent solderability

  • Bondable

  • Customizable aesthetic appearance

Select Applications / Industries

  • Electronics

  • Semiconductors

  • Jewelry making

  • Medical / Dental

  • Optical

Physical Properties / Specs

  • Coating Thickness:

    • Dependent on the Class called for

      • Generally ranges between .00002 and .0015 inches minimum

    • Class 00 – .00002 inches minimum

    • Class 0 – .00003 inches minimum

    • Class 1 – .00005 inches minimum

    • Class 2 – .0001 inches minimum

    • Class 3 – .0002 inches minimum

    • Class 4 – .0003 inches minimum

    • Class 5 – .0005 inches minimum

    • Class 6 – .0015 inches minimum

  • Hardness

    • Dependent on the Grade called for

    • Grade A – 90 Knoop maximum

    • Grade B – 91-129 Knoop maximum

    • Grade C – 130-200 Knoop maximum

    • Grade D – 201 Knoop and over

  • Aesthetic Appearance:

    • Yellow to orange color depending on the finish of the underplating materials and the process used

    • Finish will range from matte to bright depending on the substrate material


  • Ferrous: All ferrous alloys including many Steel alloys

  • Cuprous: Pure Copper and all cuprous alloys including Copper Molybdenum, Copper Beryllium (BeCu), Copper Tellurium (TeCu), Brass & more

  • All Aluminum Alloys Including Wrought, Cast and Proprietary Alloys (MIC-6)

  • Exotics & Others: Inconel, Kovar, Monel, Tellurium, Magnesium, Nickel, Lead & more


A layer of nickel (whether it be sulfamate or electrolytic) typically is applied between gold and the base material (substrate). The chosen underplate material has a direct impact on the luster of the gold finish. Sulfamate Nickel is typically more matte, meaning the gold deposit will also be matte. Electrolytic nickel yields a brighter deposit, making the gold deposit a brighter gold finish.

  • Electrolytic Nickel

  • Electroless Nickel

  • Sulfamate Nickel

  • Copper

  • Silver

Pre-Treatments Available

  • Mechanical Cleaning

  • Custom Masking

  • Chemical Films

  • Hydrogen Embrittlement Stress Relief

Post-Treatments Available

  • Laser Marking

  • Engraving

  • Chemical Films

  • Hydrogen Embrittlement Stress Relief

Types & Grades

  • Types – I, II and III (in both Soft and Hard formulations)

  • Grades – A, B, C, and D

  • Classes – 00, 0, 1, 2, 3, 4, 5, 6

Specs & Certifications

  • AMS 2422 --- ROHS Compliant

  • AMS 2425 --- NADCAP Approved, ROHS Compliant

  • ASTM B488 --- NADCAP Approved, ROHS Compliant

  • MIL-G-45204 --- NADCAP Approved, ROHS Compliant

  • MIL-DTL-45204 --- NADCAP Approved

  • Various company specifications

Please Note

  • If the hardness grade for the gold coating is not specified Type I shall be furnished at hardness Grade A, and Type II shall be furnished at hardness Grade C

  • For soldering a thin purity soft gold coating is preferred

Contact Us

Depending on your end goals one of AOTCO’s range of Gold Plating processes could be an excellent option for your surface finishing needs. If you have a unique part, specialized needs or simply want to work with the best, please reach out and let us know how we can help you achieve the results you need.

Metal finishing in Massachusetts from AOTCO


For help identifying the type of Soft or Hard Gold and underplating substrate for your job simply contact us to get things started.

If you need a finishing partner who will listen carefully and then Make it Happen for You, call AOTCO at 1 888 275 0880

Since 1975 AOTCO Metal Finishing LLC has delivered outstanding results for clients with the toughest requirements for metal finishing.

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