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Zinc electroplating is one of the most popular methods that are used all around for the purpose of electroplating. It is a very cost-effective process, and is mostly used to provide a protective coating to metallic substances such as nuts, bolts, fasteners, automotive parts, and many other hardware items. Besides this benefit, the use of zinc also improves the overall appearance of the metals, by giving them a variety of colors, a clean look, brightness, and a nice glowing shine. Fully Automatic Plating is used in the metal finishing carrying components held commonly in Racks or Barrel Automatic Plants are direct savings in labour cost. Better process application and production control, improved solution maintenance and quality control.
Zinc Plating Process:
The electrocoat process can be divided into four distinct steps:
1. Cleaning of the Substrate
2. Activation or Pickling
3. Zinc Electroplating
4. Rinsing and Drying the Finished Product
Cleaning of the Substrate :
Cleaning of the substrate is done in order to remove any dirt, rust, oil, etc., from the surface. An alkaline detergent is used to clean the surface to ensure the zinc electroplating is of good quality, and the plating remains intact for a long period of time. Improper cleaning usually results in a variety of plating defects like peeling or blistering over a period of time. The process of cleaning an object involves two steps: alkaline bath and electro cleaning. Soaking the metal in an alkaline bath for 5 - 10 minutes, at about 55-60°C is usually enough to get rid of most of the soil and dirt. After this, the parts are cleaned further in an electro cleaner. An electric charge is applied to the metal either at its cathode or anode ends, which results in the release of oxygen or hydrogen from the solution, cleaning the parts at a micro level. The time and temperature factors are much the same as for the alkaline soak process.
Activation or Pickling :
Activation or pickling of the metal involves removal of oxides and scales from the surface by using various acid solutions. These layers of oxides and scales are formed on the metal surface during their manufacturing, or while storage and handling. Pickling is commonly done using acids like sulfuric acid or hydrochloric acid. The type of metal and the thickness of the scales present on the metal decide the type of acid, the dipping time, and the temperature required for activation process.
Zinc Electroplating :
Proper cleaning and activation of the parts ensure that they are ready for zinc electroplating. The metal parts are first washed using water, followed by placing them into an aqueous solution, like alkaline cyanide. Then, a direct current (DC) is applied at the anode for a fixed amount of time. This results into the deposition of zinc ions at the cathode, i.e. the metal surface. For achieving uniform electroplating, it is necessary that the anode and the cathode are positioned suitably into the aqueous solution and the current flows uniformly over the entire area of the metal surface. If the current flow is not uniform, it will lead to thicker layers of zinc plating over the areas receiving more amount of current, while forming thinner layers over the recesses.
A variety of chemical agents are used along with zinc electroplating in order to achieve the desired chemical and physical properties of the final product. The properties can be altered by suitable variations in the chemical agent being used, duration of soaking, electric charge applied, and the time and temperature factors.
Rinsing and Drying the Finished Product :
The general rule is to rinse the parts with water after every step of the electroplating process. After the metal has been electroplated, it is washed in a water container to remove any contamination of the surface. In case of more contamination, water rinsing may be done multiple times. The parts are either cleaned in a rinsing tank or under running water, depending on the level of contamination and the extent to which the surface needs to be diluted in order to remove the contamination, followed by drying.
Benefits of Zinc Plating
• Adds anti-corrosion properties to materials.
• Offers an attractive finish.
• Low cost treatment.
• High Strength.
• Recyclability.
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