Corrosive metal parts in conjunction with leather are a common phenomenon that affect shoes, bag closures and belt buckles, as well as rivets or buttons. Over time, the metal parts become dull, rust, change their colour or coatings peel off. There is rarely a single cause, since the speed and extent of metal corrosion can be directly attributed to several factors:
- The alloy constituents and the method of processing the metal element (coating, surface treatment).
- The type of leather, the finish and tanning of the adjacent leather.
- The environmental conditions directly affecting both materials.
Investigations have shown that there are leathers which can promote corrosion, particularly chromium-free tanned leathers. The exact mechanism has not yet been clarified. It is thought to be an interaction of acidity and chloride content in the leather. The slightest traces of sulphide compounds, such as those used in the liming process, can blacken silver. This also applies to the effects of hydrogen sulphide and sulphur dioxide from the air. If these emissions are intensified by moisture (rain, but also sweat), the toxins are thus bound to the metal by moisture and the corrosion can accelerate significantly.
If the metal parts have manufacturing faults, they are more susceptible to corrosion. They may have been poorly prepared for subsequent layers of coating, which result in uneven application.
In order to prevent corrosion, a prevention control is required in the production process.