Electroplating Notes - PDF

CHAPTER 11 - NOTES - PART 2 Chemical Effects Of Electric Current When an electric current is passed through an electrolyte , Chemical reactions takes place. This is called chemical effects of electric current. The passage of an electric current through a conducting solution causes chemical reaction....

CHAPTER 11 - NOTES - PART 2 Chemical Effects Of Electric Current When an electric current is passed through an electrolyte , Chemical reactions takes place. This is called chemical effects of electric current. The passage of an electric current through a conducting solution causes chemical reaction. This may cause ▪ formation of bubbles of a gas on the electrodes ▪ deposits of metal on electrodes ▪ changes of colour of solutions etc. Applications of Chemical effect of the electric current: (a)Electroplating: The process of depositing a layer of any desired metal on another material by means of electricity is called electroplating. It is one of the most common applications of chemical effects of electric current. Uses of Electroplating: Electroplating is widely used in industry for coating metal objects with a thin layer of a different metal. This may be done to ▪ make objects appear shiny ▪ prevent corrosion ▪ make objects resistant to scratches ▪ coat less reactive metal on more reactive metals to protect from getting spoilt Applications of Electroplating  Medical equipment is made up of Nickel which is harmful to the human body hence to avoid it from coming in contact with our body a coating of platinum or gold is applied on the surface of Nickel.  Many kitchen equipments, bath taps, parts of cars etc. are covered with Chromium coating. Chromium is an expensive metal hence the objects are created with the cheaper metal and Chromium coating is provided. Thus to bring a shining over the objects and prevent them from corrosion, Chromium coating is used.  Jewellery makers often make ornaments of less expensive metals and provide a coating of Gold or Silver upon them.   The Tin cans that are used to store food are actually made up of Iron and have a coating of Tin on them. Iron can easily react with food and spoil it, however Tin prevents the food from getting reacted with Iron and therefore helps in preventing it from getting spoiled easily.  Bridges and various parts of automobiles are made up of Iron because it provides strength. However in order to prevent Iron from getting rusted a coating of Zinc is provided over it. This method is also called galvanization of Iron. Points to remember Metal to be coated on another material should be taken at the positive terminal of the battery. Material (Object) on which coating has to be done is always taken at the negative terminal of the battery. The solution must contain the ions of the metal which you want to coat. Example: To plate silver on an iron spoon. So, silver is taken at the positive terminal, iron spoon at the negative terminal and the solution taken contains silver ions. (b)Purification of metals: Example: Here copper is purified  Impure copper at the positive terminal. Pure Copper at the negative terminal. Electrolyte: A solution of copper sulphate