1. The reason for the discoloration of the zipper made of stainless steel:
When used on stainless steel products or wool products, the stainless steel zipper will cause some teeth to turn black due to metal oxidation. This is because when the leather-making agent for leather and the processing bleaching agent for woolen products remain on the product during the treatment process, the gas of the product will cause discoloration of the stainless steel zipper.
Example of chemical reaction: Oxidative bleach (H2O2) → black (CuO) or red (CuO2);
2. Reasons for discoloration of metal zippers bundled with rubber bands:
The rubber band itself contains sulfide. When the metal zipper is bundled with the rubber band, the metal teeth will be vulcanized (blackened).
Example of chemical reaction: the condition of excess sulfide or HS2 gas → black [CuS].
3. Causes of discoloration caused by contact with acidic compounds or chromium compounds.
Examples of chemical reactions: acidic compounds and chromium compounds [Cr2O3] → black [CuO, red [CuO2] or blue [CuSO4].
About color
1. Light source: D65---international standard light source;
2. Standard: QB/T 2171～2173-2001 stipulates that it reaches level 4;
3. Color sample:
a. The size of the color sample must be larger than 4×4cm2;
b. The color sample must be marked on the front and back;
c. The color of wool and reflective fabrics is not allowed.