White gold does not rust, but its appearance often changes over time due to its chemical composition and necessary maintenance. Rust is a specific form of iron oxidation, and because white gold does not contain iron, it cannot rust in the traditional sense. The changes observed in white gold jewelry, such as dulling or yellowing, result from tarnish, which is a chemical reaction involving the non-gold metals within the alloy, or the wearing away of a protective coating. This discoloration is a common characteristic that requires proper care to maintain the metal’s bright, silvery luster.
Understanding Rust and Gold Chemistry
Rust is the common term for iron oxide, a reddish-brown compound that forms when iron reacts with oxygen and water through oxidation. Pure gold (Au) is classified as a noble metal, meaning it is highly resistant to chemical attack and oxidation under normal environmental conditions. This chemical stability prevents pure gold from oxidizing, corroding, or rusting, which is why ancient gold artifacts retain their shine. While rust is specific to iron, other metals can undergo different forms of corrosion or tarnish when exposed to air, moisture, or certain chemicals.
The Composition of White Gold
White gold is an alloy, a mixture of pure yellow gold and one or more white base metals. To achieve the desired pale color, metals like nickel, palladium, silver, and zinc are mixed in. Purity is measured in karats; for example, 18-karat white gold is 75% pure gold and 25% alloy, and 14-karat is 58.3% gold. While the gold content remains chemically inert, the white base metals are susceptible to tarnish or oxidation. These alloy metals, particularly copper or silver, can react with sulfur compounds or chemicals to create a dull appearance.
Why White Gold Requires Replating
The underlying white gold alloy often retains a slight yellowish tint from the pure gold content. To achieve the brilliant, mirror-like white finish, the jewelry is coated with rhodium, a rare and highly reflective member of the platinum family. This rhodium plating provides the signature bright-white color and adds durability, but the applied layer is very thin, typically measuring less than a micron thick. The rhodium layer is not permanent and gradually wears away due to friction, causing rings to show wear faster than necklaces. Exposure to abrasive chemicals, such as chlorine or household cleaning products, accelerates this erosion, making the yellowish alloy visible and requiring periodic professional maintenance.
Preventing Tarnish and Maintaining Luster
Maintaining the bright finish of white gold involves protecting the rhodium plating and the underlying alloy from corrosive exposure. Remove white gold jewelry before engaging in activities that involve harsh chemicals, such as cleaning with bleach or swimming in chlorinated pools. Personal care products like hairspray, perfumes, and lotions can also accelerate plating wear, so apply these items before putting on jewelry. Proper storage helps prolong the luster; store pieces separately in a soft pouch or fabric-lined box to prevent abrasion. To fully restore the bright white color, professional rhodium replating is necessary, typically recommended every 12 to 24 months depending on how frequently the jewelry is worn.