Jump to: Rust x Tarnish x Stain | What Makes Gold Special? | Does Gold Corrode? | Gold's Stability | Alloys and Gold Tarnish | Tarnish and Value | Gold Coins Durability | Preventing Tarnish | Investing in Gold
In short, no. Pure gold is celebrated for its remarkable rust, corrosion, and tarnishing resistance. It stands the test of time and affirms its status as one of the most valued and enduring precious metals. Nowadays, bullion gold coins and bars crafted from the highest purity possible (.9999 fineness) retain their pristine appearance indefinitely due to gold’s chemical resistance.
Gold remains unaffected, unlike some metals, such as iron, which rust when exposed to oxygen and moisture. However, it can become susceptible to tarnishing when alloyed with specific materials to create gold alloys, depending on the specific composition.
This explains why some gold items, like gold jewelry or coins, may develop a tarnished or stained appearance.
Key Takeaways:
- Pure gold is immune to rust, corrosion, and tarnish due to its remarkable chemical stability, while gold alloys may tarnish depending on their composition.
- Rust occurs in metals containing iron, tarnish results from surface reactions with air compounds like sulfur, and stains are caused by contact with external substances like oils or acids.
- To prevent tarnish, store gold items in a dry, controlled environment and avoid contact with corrosive substances, cleaning them gently with mild soap and water when needed.
- Gold’s value extends beyond collectibles, with applications in medicine and electronics, and more recently as a popular hedge against inflation, cementing its role as a stable and enduring asset.
Now that you know gold alloys can experience some tarnishing, let me clarify the differences between tarnish, stains, and rust.
Rust, Tarnish, and Stain: What’s the Difference?
- Rust: Rust is a chemical reaction between iron, oxygen, and moisture, producing iron oxide. Since gold does not contain iron, it does not rust. However, if a gold layer is plated over an underlying metal like iron, the base metal may rust if exposed.
- Tarnish: Tarnish occurs on the surface due to a reaction with compounds in the air, such as sulfur. For example, silver tarnishes when exposed to hydrogen sulfide, forming a dark patina. Gold, when alloyed with other metals, may also tarnish over time.
- Stain: The stains you might observe on gold objects are discoloration from contact with other substances, such as acids, oils, or certain chemicals. The color of the stain depends on the gold alloys and the nature of the reaction.
What Makes Gold Special?
Gold’s unique properties go far beyond its aesthetic appeal. It was first discovered around 6000 BC and was one of humankind's earliest metals mined and crafted.
Gold (Au) is molecularly indestructible and exceptionally dense, ensuring its durability and lasting value. Besides, it is also highly malleable, ductile, and a superb conductor of electricity while maintaining relative softness despite its remarkable resistance.
Its unparalleled resistance to oxidation, tarnish, and chemical reactions allows it to remain unaffected even when exposed to substances that would corrode most other metals.
However, I can not say that it is impossible for gold to corrode.
Does Gold Ever Corrode?
As a fascinating fact, pure gold can be dissolved by aqua regia, also known as 'royal water.'
Aqua regia is a highly corrosive mixture of concentrated nitric acid and hydrochloric acid, typically in a ratio of one part nitric acid to three parts hydrochloric acid by volume.
This mixture primarily dissolves gold, making it invaluable for refining or separating it from other metals, such as silver.
You only go that far because the gold's stability is out of this world.
Gold's stability
Silver and gold are among the least reactive metals due to their unique electronic configurations and highly stable atomic structures.
In their outermost electron shells, silver contains a single electron in the 5s orbital (5s1), while gold has one electron in the 6s orbital (6s1), contributing to their remarkable resistance to chemical reactions.
These outer electrons are relatively far from the nucleus. They are shielded by filled inner electron shells, making them less prone to participate in chemical reactions and less likely to bond and form other elements.
The Impact of Alloys on Gold Tarnishing
Because gold is highly malleable and soft as a metal, some objects, such as coins and jewelry, tend to be crafted with alloys, such as copper, zinc, nickel, platinum, silver, and even palladium.
A standard gold alloy is copper, an easily reactive metal to the environment. So, coins and other objects made of gold and copper might tarnish a little.
1 oz South African Gold Krugerrand Coin freshly minted, made of 91.67% gold (22 karats) and 8.33% copper.
But how does that impact the value of a gold alloy object?
Does Tarnished Gold Lose Its Value?
Regarding gold coins and bullion, tarnish can alter the surface appearance but not the intrinsic value. The value of investment-grade gold items, such as bullion coins, is tied to their gold content, unaffected by tarnish.
In contrast, environmental factors like moisture, oils, and other substances may influence their perceived value for numismatic coins or gold jewelry.
Proper care can help preserve these items’ appearance and worth.
And what about the pure gold objects?
The Durability of Pure Gold Coins
As I mentioned before, gold’s durability is enhanced by its status as a noble metal, meaning it is less reactive than other metals. Gold's inertness ensures its longevity, unlike aluminum, copper, or iron, which can corrode or oxidize under normal conditions.
This is why fine gold coins, jewelry, and bars remain popular and valued across centuries, and they are recognized worldwide and highly prized.
Preventing Rust or Tarnish on Gold Items
Even though gold is highly resistant, gold alloys are more susceptible to environmental factors like moisture and exposure to acids or other compounds.
When cleaning tarnished gold objects, jewelry specialists advise using warm water and mild dish detergent to soak the jewelry and clean it with a soft cloth, never using chemicals or harsh materials.
Store gold items such as jewelry and gold bars in a dry, controlled environment to prevent the reaction. Minimize contact with oils, perfumes, and other corrosive substances that can affect their surface.
Investing in Gold
Gold, like silver, is a remarkably stable metal valued for its intrinsic worth and role as a key investment asset. Its price has historically surged during geopolitical and economic crises, cementing its reputation as a hedge against inflation.
Beyond investment, gold has diverse applications in medicine, electronics, and other fields, demonstrating its enduring importance.
