Zinc Electroplating at Home

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   / @ajrestoration   So this was my first time trying my hand at electroplating.

I hope you enjoy the video!

Electroplating is the process of coating one metal over another by using electricity, mainly done to provide protection from corrosion. Using the electroplating process enables to change of the chemical and physical properties of a metal. Electroplating is done by the process of electrodeposition and involves the formation of an electrolytic cell consisting of the cathode and the anode, immersed in an electrolytic solution. The object is to be plated and the metal is dipped into the aqueous solution containing the metal ions. When a direct current is applied to the aqueous solution, the metal at the anode begins to dissolve, and the free metal ions reach the cathode to form a thin layer of coating on the object. The object to be electroplated is also called a substrate. Zinc is mostly used to provide electroplating to steel or iron material, although many other metals can also be electroplated using zinc.

The zinc electroplating process involves the formation of an electrolytic cell consisting of two metals that form the electrodes and pass electric current to the electrolyte. While zinc forms the anode, the metal to be electroplated forms the cathode. When an electric current is passed through the aqueous solution, the zinc ions travel through the aqueous solution and attach themselves to the surface of the substrate, forming a thin plate. Zinc plating is done in a variety of aqueous solutions, like alkaline cyanide, alkaline non-cyanide, or acid chloride salt solutions.

Zinc Electroplating Steps

Step 1
Cleaning 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: an alkaline bath and electro-cleaning. Soaking the metal in an alkaline bath for 5 – 10 minutes, at about 150° F 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 end, 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.

Step 2
Activation or Pickling of the Substrate
Activation or pickling of the metal involves the 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 the activation process.

Step 3
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 is applied to the anode for a fixed amount of time. This results in 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, an electric charge applied, and the time and temperature factors.

Step 4
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, followed by drying. 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.