The substance of copper alloy will react chemically and change color easily in case of acid, alkali, oxidant or reductant. The zipper may change color when the residual chemicals on the clothing react with the teeth, pullers and tail opening parts of the metal zipper. This chemical reaction is easy to occur under high temperature and high humidity conditions. (clothes are steam ironed or sealed in plastic bags and kept for a long time, etc.). This is not a zipper quality problem.
2. Examples of discoloration due to chemical reactions
1. Steam ironing or wet in rainy days → blue [Cu (OH) 2]
2. Acid compound and chromium compound [Cr2O3] → black [Cuo, red [CuO2] or blue [CuSO4]
3. Condition of excess Cl2 gas → light yellow [CuCl2]
4. Oxidative bleach [H2O2] → black [CuO] or red [CuO2]
5 reducing bleach [Na2SO3] → black [Cuo, cus] or red [CuO2]
6. Conditions of excess sulfide or HS2 gas → black [cus]
