While true "rust" specifically affects iron and its alloys like steel, many other types of jewelry made from base metals and certain alloys can undergo corrosion, often appearing as tarnishing or discoloration.
Understanding Rust vs. Tarnishing in Jewelry
It's common to use the term "rust" broadly for any metallic discoloration, but scientifically, true rust is a specific type of corrosion.
True Rust: The Iron Connection
Rust is the common name for iron oxides that form when iron or its alloys, such as steel, are exposed to oxygen and moisture for a prolonged period. This process creates a reddish-brown, flaky coating that can weaken the metal.
- Jewelry Susceptible to True Rust:
- Inexpensive costume jewelry containing high amounts of iron or steel.
- Some industrial-style jewelry pieces made from unsealed steel.
- Components like clasps or findings on less expensive items.
Tarnishing and Other Forms of Corrosion
Most jewelry metals don't rust but instead tarnish or corrode. Tarnishing is a surface-level corrosion that results in a dull, dark, or discolored layer forming on the metal. This occurs through chemical reactions with sulfur, oxygen, moisture, or other compounds in the air or on the skin.
Copper, brass, and bronze are particularly vulnerable to tarnishing and will need maintenance to prevent their dulling effects over time. Similarly, sterling silver can tarnish easily; the presence of other metals, such as copper, zinc, and nickel, in the silver alloy makes it more susceptible to tarnishing.
Metals Prone to Tarnishing and Corrosion
- Copper: Develops a green or bluish-green layer called verdigris (patina) when exposed to air and moisture. This is a common form of corrosion for copper jewelry.
- Brass (Copper-Zinc Alloy): Can tarnish to a dull brown, green, or even black, losing its original luster.
- Bronze (Copper-Tin Alloy): Similar to copper and brass, bronze jewelry can develop green or dark brown surface layers.
- Sterling Silver (Silver-Copper Alloy): Often turns black or dark brown due to a reaction with sulfur compounds in the air, forming silver sulfide. The copper content in sterling silver significantly contributes to its tarnishing.
- Some Base Metals and Costume Jewelry: Pieces made from inexpensive alloys (often containing nickel, zinc, or other non-precious metals) can oxidize, corrode, or react with skin acids, leading to discoloration of both the jewelry and sometimes the skin (e.g., green fingers).
Common Jewelry Metals and Their Corrosion Characteristics
| Metal/Alloy | Type of Corrosion | Appearance of Corrosion | Reversibility (Surface) |
|---|---|---|---|
| Iron/Steel | Rust (Oxidation) | Reddish-brown, flaky | Difficult to reverse |
| Copper | Tarnishing/Patina | Green, brown, bluish-green | Often reversible |
| Brass | Tarnishing | Dull brown, green, dark | Often reversible |
| Bronze | Tarnishing | Green, dark brown | Often reversible |
| Sterling Silver | Tarnishing | Black, dark brown | Highly reversible |
| Costume Jewelry | Various (Oxidation) | Green, black, dull, sometimes skin discoloration | Varies by composition |
Factors Accelerating Jewelry Discoloration
Several environmental and personal factors can speed up the tarnishing and corrosion process:
- Moisture and High Humidity: Water is a key component in most corrosion reactions.
- Chemical Exposure: Perfumes, lotions, hairsprays, cleaning products, chlorine (from pools), and even certain foods can cause metals to react and tarnish rapidly.
- Skin Oils and Sweat: The natural oils, acids, and salts in human sweat can accelerate metal discoloration.
- Air Pollutants: Sulfur compounds and other airborne chemicals are common culprits for tarnishing, especially for silver.
- Storage Conditions: Leaving jewelry exposed to air and humidity can increase its susceptibility to tarnishing.
Preventing Tarnishing and Corrosion
Proper care and storage are essential for maintaining the beauty of your jewelry.
- Store Properly: Keep jewelry in airtight bags or boxes, preferably with anti-tarnish strips, in a cool, dry place away from direct sunlight.
- Clean Regularly: Gently wipe jewelry with a soft, lint-free cloth after each wear to remove oils and sweat. For deeper cleaning, use appropriate jewelry cleaners specifically designed for the metal type.
- Avoid Exposure:
- Remove jewelry before showering, swimming, or washing dishes.
- Put on jewelry after applying perfumes, lotions, and hairsprays.
- Avoid wearing jewelry during strenuous activities or when using harsh chemicals.
- Consider Protective Coatings: Some metals, like sterling silver, can be rhodium-plated, which provides a protective barrier against tarnishing. Clear lacquers are also used on some costume jewelry to prevent discoloration.
- Gentle Polishing: For tarnished items, use a specialized polishing cloth or a soft brush with a mild jewelry cleaner to gently buff away the discoloration. Always follow the product instructions. You can find more tips on caring for different metals at The Spruce Crafts.
By understanding the difference between true rust and tarnishing, and by practicing good care habits, you can significantly extend the life and luster of your cherished jewelry pieces.
