Gold Plating Technical Information

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Gold plating is typically chosen for its thermal and electrical conductivity, high corrosion resistance, infrared reflectivity, solderability, and high oxidation resistance. The most common specs are MIL-G-45204, ASTM-B488, and AMS 2424 (Link these words to their content pages). AOTCO is capable of rack plating, barrel plating, and wire plating gold. AOTCO can also plate 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 minimal metal impurities compared to hard gold, which yields high corrosion resistance and optimizes the deposit to eliminate high temperature oxidation.

Hard Gold:

In contrast, Hard Gold is a deposit that is utilized 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.

Feasible Substrates (Base metals):

Click Here to see our most common base metals and materials

Additional information (underplate and aesthetic appearance of gold deposit):

A layer of nickel (whether it be sulfamate or electrolytic) is typically applied between gold and base material (substrate). This interfacial metal is referred to as the “underplate” metal. This metal allows the gold to more effectively adhere to the customer part while minimizing quality issues and eliminating the possibility of copper diffusion into the gold deposit.

Choosing the 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.

Gold is Yellow to orange color depending on process used. Gold finishes range from matte to bright finish depending on basis material and type, grade and class of gold used. Brightness of under plating will also affect appearance.


We offer Gold Plating within the following Types/Class:

Type I: 99.7% gold minimum (Grades A, B, or C).
Type II: 99.0% gold minimum (Grades B, C, or D)
Type III: 99.9% gold minimum (Grade A only).

Grade A: 90 Knoop maximum.
Grade B: 91-129 Knoop.
Grade C: 130-200 Knoop.
Grade D: 201 Knoop and over.
Metal finishing in Massachusetts from AOTCO

At Aotco, we plate to your specified coating requirements.