How to Prevent Metal Zippers from Discoloring

With the development of the garment industry, new materials, new processes, washing processes and post-processing of ready-made garments have become increasingly diversified.

You may have experienced metal zipper teeth and pullers (copper, brass, copper-nickel-zinc alloy) becoming discolored or fabric staining during laundering or reprocessing.

In this article, we will analyze the causes of the problem and the preventive measures to eliminate or prevent it.

Discoloration of metal

It is known that copper alloys can react with chemicals such as acids, alkalis, oxidants, reducing agents, sulfides, etc., resulting in discoloration. Chemical reactions can easily occur between chemicals or residues introduced into the fabric or during laundering and the metal parts of the teeth, slides, upper and lower stops, retaining boxes and pins, causing discoloration.

These reactions occur easily in high temperature and humid environments. This can easily happen if the product is put into a plastic bag immediately after sewing, washing and steam ironing, and is stored in the bag for a long time. Chemical reactions easily occur between fabrics containing reactive dyes and copper alloys.

Wool and cotton products change color due to washing process

If zippers containing copper alloys are attached to bleached wool fabrics, discoloration will occur.

Generally speaking, the following three methods can be used to bleach wool.

Treat with an oxidizing bleach such as hydrogen peroxide

Treat with reducing bleach such as dithionite

Chlorine treatment is used for anti-shrinkage processing of finished products (chlorine group chlorinating agent)

If the chemicals involved in the above treatment methods (especially the second and third methods) are not adequately purified or neutralized, chemical gases (such as chlorine) can be introduced. In addition, in humid environments, chemicals can react with the zipper surface. If zippers containing copper alloys are bagged immediately after ironing, the teeth, sliders, upper and lower stops, buckle boxes, pins, etc. will become discolored due to volatilization of chemical substances and gases.

The fabric used should be thoroughly clean and dry.

Chemicals involved in the cleaning process should be adequately purified and neutralized.

Packing should not be done immediately after ironing.

Discoloration of leather products

Discoloration is caused by residues from the tanning agents and acids used in the leather tanning process.

Animal leather

The tanning process of leather involves a variety of tanning agents, such as inorganic acids (such as sulfuric acid), tannins containing chromium compounds, aldehyde compounds, etc.

Leather is mainly composed of animal protein, and its liquid is not easy to handle after treatment. Residue in contact with metal zippers will cause the metal to discolor due to time and humidity factors.

Testing front zippers After testing zippers The leather used in the zippers should be fully cleaned and neutralized after the tanning process.

Clothing should be stored in a well-ventilated, dry environment.

Discoloration caused by sulfides

Sulfur dyes are dyes that are soluble in sodium sulfide. Mainly used for low-cost dyeing of cotton fiber and cotton-fiber blended fabrics. Sulfur black, the main type of sulfur dye, will react with zipper teeth containing copper alloy in high temperature and humid environments to produce copper sulfide (black) and copper oxide (brown).

Based on the tests, it can be concluded that the discoloration is due to the presence of sulfur dyes in the fabric.

Factors such as temperature, test time, pH value, chemical dosage, etc. should be paid attention to.

Clothing should be thoroughly cleaned and dried immediately after treatment.

Discoloration and discoloration of sewn products due to the use of reactive dyes

Reactive dyes used for dyeing cotton and linen products contain metal ions. A reduction reaction occurs between the dye and the copper alloy, causing fabric discoloration or discoloration. Zippers containing copper alloys can also become discolored due to the presence of reactive dyes.

Decolorization and discoloration of copper alloy zipper cloth

Clothing should be thoroughly cleaned and dried immediately after treatment. You can also use strips of fabric to separate the zipper from the fabric.

Corrosion and discoloration caused by the use of industrial cleaning pens

Industrial cleaning pens are widely used in the clothing industry and are mainly used to deal with oil stains generated during the sewing process. However, due to the strong acidity of industrial cleaning pens, contact with zippers containing copper alloys will cause the latter to corrode and discolor.