Causes and solutions of mildew spots on electroplating parts

by | Dec 22, 2021 | 0 comments

mildew spots on electroplating parts

Causes of mildew on electroplating parts

We often find that there are some small white spots on the electroplated parts, which are difficult to wipe off, affecting the appearance of the product and even leading to scrap. This is a relatively common electroplating part problem, called electroplating parts mildew. There are two reasons for mildew on electroplated parts. On the one hand, it is caused by irregularities in the electroplating process, that is the reason for the production stage. On the other hand, it is caused by the irregularity of electroplating parts during transportation and storage, that is the reason for the logistics storage stage.

Mildew spots on electroplated parts during production

During the production process of electroplated parts, mildew and rot microorganisms are easy to adhere, so that the electroplated parts form mildew spots. The electroplating project will generally go through: upper hanger → degreasing → water washing → hydrophilic → roughening → water washing → neutralization → water washing → pre-dipping → catalysis → water washing → degumming → water washing → electroless nickel plating → water washing → acid activation → flashing Copper plating→water washing→acid activation→acid copper plating→water washing→acid activation→water washing→multi-layer nickel plating→water washing→acid activation→bright chrome plating→water washing→drying→hanger→inspection→packaging→warehousing, etc. cumbersome process. In this process, the raw materials, water, personnel, dust, etc. entering the electroplating workshop may bring in moldy microorganisms and their spores. As long as moldy microorganisms have enough moisture (humidity), even if there is no external nutrients at all, as long as the humidity If the conditions such as humidity and pH value are suitable, mold spores can also develop to a certain extent by relying on the nutrients stored by themselves. Therefore, electroless nickel plating tanks, washing tanks after electroless nickel plating, washing tanks with bright chrome plating, products with insufficient drying, gloves for inspection and packaging workers, packaging and storage supplies, etc. are all important places and stages for mold-rot organisms to effectively attach. , once moldy microorganisms or their spores exist and survive in these places, it will cause mildew spots on electroplated parts.

Mildew spot solution for electroplated parts in production stage:

In the production stage, it is necessary to prevent the occurrence of mildew spots on electroplating parts by controlling the source of mildew microorganisms, and sterilize them at the stage and place where they are effectively attached, so as to eliminate the survival conditions of mold microorganisms as much as possible.
The specific solutions are as follows.

  • Pay attention to ventilation, dust removal and sterilization of workshops and warehouses, and minimize or eliminate the source of moldy microbial contamination as much as possible.
  • Keep raw materials clean and hygienic. For example, the sodium citrate solution used for electroless nickel plating should be heated to about 80℃ for sterilization before adding.
  • The water used should be sterilized. The ion exchange resin in the water purification treatment device should be regularly sterilized and cleaned with formaldehyde or ethanol; after electroless nickel plating, an appropriate amount of formaldehyde should be added to the washing tank every day for sterilization, and ethanol should be used when cleaning the tank every shift; UV light must be used for washing water after bright chrome plating Light sterilization.
  • The temperature and time for drying the electroplated parts must be sufficient, and it is absolutely forbidden to have water on the workpiece after drying.
  • The white gauze gloves used by the inspection packers must be dry and clean, and plastic film gloves should be worn inside.
  • Electroplating parts should not be placed in a high temperature and high humidity workshop for too long, and should be quickly moved to the warehouse after packaging.

Mildew spots on electroplating parts generated during logistics storage

The mildew spots of electroplated parts during the logistics storage stage are mainly caused by the humid and high temperature environment. When relative humidity >65%, a uniform and thin water film will be formed on the metal surface through capillary adsorption, coupled with the periodic change of humidity, condensation will form, and then a micro-battery will be formed, which is electrochemical corrosion. That is the plating layer is oxidized and corroded.

Mildew solution for electroplating parts in logistics storage stage:

In the logistics storage stage, the prevention of mildew on electroplated parts is mainly achieved by controlling the relative humidity. The specific solutions are as follows.

  1. The electroplating parts are preferably packed in vacuum packaging bags to directly isolate the influence of the external environment. An appropriate amount of small packets of Chunwang desiccant should be placed in the bag.
  2. During the logistics and transportation process, keep the interior of the transport vehicle clean and dry, and hang an appropriate amount of Chunwang container desiccant according to the size of the space.
  3. During the storage process, ensure that the storage environment is dry and ventilated.
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