Gold is a popular metal that is known for its shine and luster. Many people enjoy the look of gold and use it to add a touch of luxury to their lives. And while gold is primarily known for its ornamental value, it also has several practical uses. For instance, many industries, including aerospace, automotive, and telecommunications, utilize gold for its electrical conductivity and corrosion resistance properties.
However, pure gold is expensive and can be impractical for some applications. That’s where gold plating comes in. This process offers a budget-friendly option for those who want pure gold’s functionality, practicality, and effectiveness without its high price tag. But what exactly is gold plating, and how does it work?
This guide will introduce you to the basics of gold plating. We will cover the following topics to help you better understand this process:
- What is gold plating?
- What metals can be gold-plated?
- What is the gold plating process?
- How long does gold plating last?
- Gold plating for aerospace
- Gold plating services
So read on to learn everything you need to know about gold plating.
What Is Gold Plating?
Gold plating is a process where a thin coat of gold is layered onto the surface of another base metal. This process was invented in 1805 by Luigi Valentino Brugnatelli, a famous Italian chemist who electroplated a thin layer of gold onto silver.
Until recently, gold plating was mostly used for decorative purposes – to add a luxurious touch to jewelry, watches, or other objects. However, gold plating is now used in various industries, including electronics and aerospace.
How Does It Work?
To better understand how gold plating works, let’s first understand the properties of gold.
Gold is a noble metal, which means it is resistant to corrosion. It is also an excellent conductor of electricity, meaning it can easily connect and carry electrical signals.
Therefore, when gold is deposited onto the surface of another metal, a barrier is created that prevents oxygen and other corrosive elements from coming into contact with the metal. This makes gold plating an ideal solution for protecting metals that are exposed to harsh environments.
Also, because gold is such a good conductor of electricity, it is often used to coat electrical contacts – like the ones found in computer processors – to ensure a smooth flow of electrical current.
How Much Gold Is Used?
The amount of gold used to plate an object depends on the desired thickness of the gold layer based on its application. The thickness is measured in microns – with 1 micron equaling one one-thousandth of a millimeter (1/1000 mm).
Generally, items exposed to more wear and tear – like jewelry that get rubbed against clothes – will have a thicker layer of gold than items that don’t see as much wear and tear – like electrical contacts, which are used in a controlled environment.
For example, a typical gold-plated piece of jewelry would have a layer of anywhere from 1 to 3 microns, while an electrical connector would have a layer of 0.1 to 0.3 microns.
Therefore, based on this example, it would require more gold to plate a piece of jewelry than an electrical connector.
What Grade Of Gold Is Used?
There is no one-size-fits-all answer to this question, as the grade of gold used for plating depends on the application.
For example, while pure gold (24 karats) is often used in the semiconductor industry, where a high level of conductivity is required, lower grades of gold – like 18 karats – are often used for plating jewelry because they are more durable.
What Metals Can Be Gold Plated?
Gold plating can be done on various metals, including stainless steel, copper, titanium, brass, nickel, tungsten, and silver.
Of these metals, silver is the most popular choice for gold plating because it provides a strong foundation for the gold layer and produces a more lustrous finish.
However, when silver is used as the base metal, a layer of copper is often applied first to help slow down the tarnishing process before the gold layer is applied.
What Is The Gold Plating Process?
As mentioned earlier, gold plating is the process of covering another metal with a thin layer of gold. And as simple as that definition may sound, a lot goes into the gold-plating process. Let’s take a closer look.
Gold Plating Steps
Below are the steps to gold plating including:
Step 1: Preparation
First, have the surface you want to gold plate, clean and free of any dirt, oils, or contaminants. You can do this by using various methods, including ultrasonic cleaners, alkaline cleaners, solvent cleaners, or a simple soap and water solution.
This step is crucial for ensuring that the gold adheres properly to the surface while keeping the plating tanks clean and free from contamination.
Step 2: Rinse
Have the surface you are going to gold plate rinsed with distilled water and dried completely before moving on to the next step. This helps remove any leftover cleaner residue and gives you a clean slate to work with.
Step 3: Strike
In this step, a strike layer (a thin plating layer) of high-quality nickel is applied to the surface of the clean base metal. This helps improve the adhesion of the gold to the surface and also helps prevent tarnish that can occur down the road.
Step 4: Second Rinse
After the strike layer has been applied, rinse the surface again with distilled water to help remove any impurities that may be present.
Step 5: Coating
Once you confirm the temperature, time, and voltage have been set correctly, hang the piece of metal you want to gold plate from a negative hook (cathode bar) and lower it into the gold solution.
Once submerged in the solution, an electrical charge will be applied, causing the negatively charged metal to attract the positively charged ions present in the solution. This will cause a thin layer of gold to be deposited on the surface of the metal.
It’s important to note that the layer of gold will increase in thickness the longer the piece is left in the solution.
Step 6: Third Rinse
Finally, rinse the gold-plated surface with distilled water for a final time to help remove any impurities that may be present, and hang the piece up to dry completely.
How Thick Should The Gold Plating Be?
The thickness of the gold layer will depend on the application of the gold-plated piece.
For example, a thin gold coating (0.1 – 0.3 microns) is often used in low-contact applications, especially where excellent solderability is required, like in the electronics industry.
In contrast, a thicker gold coating (1 – 1.5 microns) is often used for applications where corrosion and chemical attacks are a concern, like in the aerospace industries.
However, it’s important to note that certain rules and regulations govern the gold plating industry. These rules provide clear guidelines for the minimum and maximum thickness that can be used for various applications.
In the U.S, the Federal Trade Commission (FTC) is the body that oversees the gold plating industry and enforces these regulations. These rules and regulations can be found in the Code of Federal Regulations, Title 16, Commercial practices, Part 23.1
How Long Does Gold Plating Last?
The answer to this question will depend on various factors, including the thickness of the gold coating and the environment the gold-plated piece is subjected to.
Generally, a thicker gold coating will last longer than a thinner one. This is because the thicker coating is more resistant to wear and tear, as well as corrosion and chemical attacks.
The environment the gold-plated piece is subjected to will also affect how long the gold coating lasts. For example, a gold-plated piece subjected to salt water or other corrosive materials will only last for a short time compared to a piece used in a controlled environment.
However, it’s important to note that gold plating is not a permanent solution. Over time, the gold coating will eventually wear away, exposing the underlying metal. Also, it fades and loses its luster with time.
But generally, with proper care and maintenance, gold plating can last up to 2 years.
Does Gold Plating Tarnish?
The answer to this question is a bit complicated.
As discussed earlier, gold is a noble metal that is resistant to tarnishing. However, the other metals often used in gold plating (e.g., copper, silver, nickel, etc.) are not as resistant to tarnishing.
Over time, these metal molecules transfer into the “thin” layer of gold, causing it to break down. Eventually, the base metal comes on top of the gold coating and comes into contact with the air and oxygen (elements that cause tarnishing), causing the entire gold-plated piece to tarnish.
Gold Plating For Aerospace
In the aerospace industry, gold plating is often used on various parts and components to improve their performance. This industry utilizes gold plating mainly for its mechanical and electrical properties.
Mechanical Properties
This includes things like wear resistance, friction reduction, and corrosion resistance. All of these properties are important in the aerospace industry because they can help extend the life of parts and components and improve their overall performance.
Electrical Properties
This includes things like conductivity and resistance. Gold is an excellent conductor of electricity and has a very low resistance. This makes it ideal for use in electronic components and other applications where conductivity and resistance are important.
In the aerospace industry, gold-plated components, including barrels, connector pins, electrical contacts, sensors, and switches, often exhibit excellent corrosion resistance, wear resistance, high hardness, high conductivity, improved solderability, and excellent performance at high temperatures.
Gold Plating Services
Different metal finishing companies offer different gold plating services based on specific needs and applications. A few common gold plating services include:
Type I: Requires a minimum of 99.7% gold, with a Knoop hardness of 130-200. This gold plating service is often used for wear resistance, solderability, and wire wrap, among many other electrical applications.
Type II: Requires a minimum of 99.0% gold, with a minimum Knoop hardness of 201. This gold plating service is often used for general purposes where wear resistance is the primary focus.
Type III: Requires a minimum of 99.9% gold deposits, with a maximum Knoop hardness of 90. This gold plating service is often used for high-temperature applications, thermocompression bonding, as well as in solderability.
Also, it’s important to note that in some instances, it may be necessary to perform gold plating to meet engineering or military specifications. In these instances, special rules and guidelines must be adhered to in order to ensure a quality finish.
How Much Do They Cost?
The cost of gold plating can vary significantly, depending on the type of service you require and the size of your parts. Generally speaking, gold plating can range anywhere from a few dollars to thousands of dollars. As such, it’s important to consult with an experienced metal finishing professional before making any decisions.
Get Started With Valence Surface Technologies
As we have seen, gold plating is an excellent choice for various applications, especially in the aerospace industry. It offers excellent wear and corrosion resistance, as well as high hardness, conductivity, solderability, and performance at high temperatures. All these features make it an ideal choice for parts and components that require superior performance.
However, selecting the right gold plating service for your particular needs can be challenging, especially if you are new to the world of gold plating. Be sure to maximize the information provided in this guide to help you make an informed decision.
If you have any questions or need help with gold plating services, Valence Surface Technologies is here to help! We offer a wide range of gold plating services that are sure to meet your needs. Request a quote today for the gold plating service you need, or contact us to learn more about our services.
Sources:
- The Federal Register. Federal Register :: Request Access. (n.d.). Retrieved from https://www.ecfr.gov/current/title-16/chapter-I/subchapter-B/part-23 Issuing Authority This technical assistance document was issued upon approval of the Chair of the U.S. Equal Employment Opportunity Commission., & This technical assistance document was issued upon approval of the Chair of the U.S. Equal Employment Opportunity Commission. (n.d.). Employment tests and selection procedures. US EEOC. Retrieved from https://www.eeoc.gov/laws/guidance/employment-tests-and-selection-procedures