1. material: copper alloy is metallic copper, which is made by adding other metals and belongs to alloy metal. 18K gold is an alloy of gold and other metals with a gold content of 75%.
2. Color: The color of copper alloy is relatively dark, and there are three common colors: red, yellow and white. 18K gold is more colorful, including yellow, white and red.
3. Price and value preservation: Copper alloy is cheap and suitable for making affordable jewelry. 18K gold is relatively more valuable, which is suitable for making high-grade jewelry or collecting jewelry.
4. Durability: Copper alloy has good corrosion resistance and weather resistance, and is suitable for making outdoor ornaments. 18K gold is soft, which may be worn for a long time and needs regular maintenance.
5. Allergy: Copper alloy may cause allergic reaction and is not suitable for people with allergic constitution. 18K gold is relatively stable and can be worn by most people.
To sum up, the choice of 18K gold or copper alloy should be comprehensively considered according to personal needs, budget and allergy.