Q: Why does my zipper turn white and oxidised after storage?
White or powdery oxidation is corrosion of a metal part, and it is driven by moisture, salt and time. Storage conditions are the first thing to check, because a fault that appears only in opened bags is not a plating escape.
- Note the storage time, humidity and whether the goods were near a wall or floor.
- Inspect whether oxidation is on the slider, the teeth or both.
- Check the packaging for a desiccant and for a sealed bag.
- Compare an opened bag with an unopened one from the same lot.
- Test a sample with a light wipe to see whether the film is surface only or has pitted the metal.
Corrosion confined to opened bags points to storage and humidity. Corrosion across sealed stock suggests a finishing or passivation problem. Keep goods in a dry ventilated area within a working humidity range and rotate stock, because corrosion is time-dependent and old stock will always look worse than new.