What causes 18K gold plated jewelry to tarnish?
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- Issue Time
- Sep 18,2026
What causes 18K gold plated jewelry to tarnish?
Tarnish is a reaction on the brass base, not on the gold itself. Gold is a noble, chemically inert metal, but the copper and zinc in brass oxidise when they meet oxygen, moisture and sulfur compounds in the air — producing the dark or greenish film people call tarnish.
The three main triggers
- Friction: daily rubbing against skin, clothing and surfaces thins the 0.1-0.3 micron gold layer at contact points such as ring shanks and clasp edges.
- Chemicals: perfume, hairspray, sunscreen, soap and chlorine soften the surface film and speed up reaction at any exposed spot.
- Air and humidity: oxygen and moisture oxidise the base, and atmospheric sulfur darkens it further.
Because a plated layer is thin by design, tarnish becomes possible wherever friction or chemicals breach the coating. A continuous, polished gold layer plus correct wear and dry storage keeps the brass sealed and slows the process sharply. Hengdian (HD) Jewelry applies a measured 0.1-0.3 micron 18K gold layer over polished brass as our production standard.