Genuine gold necklace may change color over time. The composition of an 18k gold necklace is 75% pure gold and 25% alloy. A 14k gold necklace has almost twice the amount of alloys at 42%.
If you're wearing your gold necklace while using harsh detergents around or body sweat or in shower or in a pool or spa that has been treated with chlorine, your gold necklace will experience corrosion.
When these chemicals react with the metal alloy in the gold necklace.. it will cause those metals to corrode there for color issue. For example, if you wore your gold necklace in the shower and it turned green, that's because of the chemical reaction between the water and the alloys in your gold necklace. Water is not damaging to gold, but the harsh chemicals in water can accelerate the tarnishing process. Body sweat can also cause your gold necklace to discolor, especially if you wear it every day. The acids in sweat can react with the alloys in gold, causing it to tarnish.
If you want to keep your gold jewelry looking its best, it's important to clean it regularly and avoid exposure to chemicals and other elements that can cause it to tarnish.
