A gold chain will not rust, but it can show signs of corrosion and discoloration often mistaken for rust. Rust is the specific term for the oxidation of iron, a process that forms flaky, reddish-brown hydrated iron oxide. Since gold chains do not contain iron, they cannot rust chemically. The perceived damage is actually tarnish or verdigris, which results from a reaction involving the other metals mixed with the gold.
The Chemistry of Pure Gold
Pure gold (Au) is classified as a noble metal, meaning it exhibits exceptional resistance to chemical reactions. This stability is why 24-karat gold, which is 99.9% pure, does not corrode or tarnish under normal conditions. Gold’s electron configuration is highly stable, making its outer electrons less available to bond with other elements.
This inert nature means gold will not react with oxygen or water, the two main ingredients required for iron to form rust. Rusting is an oxidation process where iron loses electrons to oxygen; gold’s atomic structure makes this electron transfer unfavorable. Even when exposed to air and moisture for centuries, pure gold retains its original metallic sheen.
Why Gold Chains Appear Damaged
Most gold chains are not made of 24-karat gold because pure gold is a relatively soft metal that would easily bend, scratch, and wear down with daily use. To increase durability, gold is alloyed, or mixed, with stronger base metals like copper, silver, and nickel. The purity of the gold is measured in karats, with lower karat numbers indicating a higher percentage of these non-gold alloying metals.
For example, 14-karat gold is 58.3% pure gold, with the remaining 41.7% made up of other metals, most commonly copper and silver. These alloy metals react with substances in the environment, causing visible damage on the chain. Sweat (which contains salts and acids) and chemicals found in lotions, perfumes, or cleaning agents can accelerate the oxidation of the copper and silver components. The higher the proportion of these reactive metals, such as in 10-karat gold, the more susceptible the chain is to discoloration.
Recognizing Tarnish and Verdigris
The discoloration seen on a gold chain is typically one of two forms: tarnish or verdigris. Tarnish appears as a dark, dull layer, often black or gray, primarily caused by the silver content in the alloy. Silver reacts readily with sulfur compounds in the air, such as hydrogen sulfide, to form silver sulfide, which creates the dark surface film. This reaction occurs even with low concentrations of sulfur compounds found in pollution or certain fabrics.
Verdigris is the distinct greenish or bluish-green residue that forms on a chain, signaling copper corrosion. Copper in the alloy reacts with oxygen, moisture, and chloride from sweat to form copper salts, often copper carbonate or copper chloride. This green coloration may transfer onto the skin, especially in individuals with more acidic sweat chemistry. In both cases, the discoloration is a surface phenomenon involving the alloy metals, not the gold itself.
Maintaining Luster and Preventing Corrosion
Preventing discoloration of gold chains involves minimizing exposure to common corrosive agents and maintaining a clean, dry surface. Always remove the chain before showering, swimming, or engaging in activities that cause heavy sweating, as moisture and chlorine accelerate tarnish and corrosion. Chemicals found in household cleaners, bleach, and personal care products like hairspray and perfume can also speed up the reaction with alloy metals. Apply all cosmetic products and allow them to fully dry before putting on your gold chain.
Proper storage is important for preservation. Store gold chains in a dry environment, ideally in an anti-tarnish cloth bag or a jewelry box with a soft lining. This reduces exposure to air and humidity, which slows the oxidation process. After each wear, gently wipe the chain with a soft, lint-free cloth to remove sweat, oils, and residues. For occasional cleaning, soak the chain in warm water with a few drops of mild dish detergent, followed by a soft brushing and thorough drying.