In general, gold doesn't really change color. But since it's a fairly soft metal, it mixes with other metals to create an alloy. Have you ever found a gold ring that had turned copper in color and wondered why? Gold jewelry discolors over time because it's not pure gold. Gold itself doesn't usually change, but it's the other components that tarnish over time.
The discoloration of gold can also be due to poor gold-plating techniques, in which the gold layer is too thin and, eventually, due to friction, wears out, revealing the base material. White gold is alloyed with silver and nickel to give it its appearance. It tends to turn yellow over time, but this can be remedied by polishing and rhodium-plating the jewelry. As a gold color, white is often considered the most “modern” or modern type of gold, but it is far from being a new invention.
In fact, it dates back to the 19th century, when palladium was used to create the metal. Again, because pure gold has a low reactivity, it's very unlikely to rust, but the other metals in gold alloys will. Pure gold never combines with oxygen, so it always stays shiny and doesn't rust, tarnish, or turn green over time. Take your white gold to the store where you bought it and they'll place a thin layer of rhodium on top of the gold, returning it to the bright white color you originally had.
Although most gold alloys tarnish over time, proper care and polishing can restore them to their original shine. For high-quality gold plating, this process is repeated several times to form several layers of gold. Therefore, during the wet season or during summer holidays by the sea, the surfaces of gold jewelry can be covered with a light layer of rust. White gold will have a different hardness and ductility depending on how it has been alloyed with the other metals.
While the value of jewelry is influenced by its classification in carats, soft gold is prone to damage due to wear and tear over time, making it necessary to mix gold with alloys to make durable jewelry. If you want to take extra precautions, you can prevent white gold from getting wet, soapy, or dirty when it's easy. Like all plated items, 18-carat gold-plated jewelry tarnishes over time and reveals the metal underneath. Gold in its purest form does not tarnish, however, the gold used for jewelry mixes with other metals, allowing it to tarnish.
Elements such as sulfur and chlorine react with the other metals in gold jewelry, causing them to corrode and turn black, thus blackening the skin underneath. On the other hand, when gold, which has low reactivity, is placed in water, steam or dilute acid baths, it will not react. Proper gold-plating techniques use pure gold, which prevents tarnishing, since the base metal with a higher reactivity is not exposed to the elements.
