why the particles of powder are given an electric charge while spraying them to form the powder coating
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Answers
An electric charge is given to the powder particles while spraying, to form a uniform layer of powder coating on the surface of a metallic object.
• Powder coating is a process of coating metal surfaces with a uniform layer of powder particles.
• While coating, the powder particles are given a negative electric charge to create an electrostatic force of attraction between the particles and the positively charged metallic object.
• This electrostatic force of attraction helps the powder particles to adhere to the metallic object strongly.
• This way, a uniform and thick coating of powder particles is created on the surface of a metallic body.
A method of applying a layer harder than paint on the surface of an iron object to prevent rusting is called powder coating. In this method, a polymer resin, a pigment and some other ingredients are melt mixed, cooled and ground into a homogeneous powder. This powder is sprayed on the polished metal surface by Electrostatic Spray Deposition (ESD). Now, the particles are given an electrostatic charge due to which a uniform layer of powder sticks to the metal surface. Then the object is heated in the oven along with the coating. A chemical reaction takes place in the layer, resulting in the formation of long cross-linked polymeric chains. This powder coating is highly durable, hard and attractive.