Name: Parth Pandya, Nehal Patel Branch: Mechanical-A-1 (DS) Subject: Material Technology Roll no.: ,

 there are two types of engineering material Metal 2. Non-metal

 In chemistry, metal is defined as an element with a valence of 1,2 or 3.  It can also defined as solids composed of atoms held together by a matrix of electrons.

 An element which is dull-colored, brittle and nonconductive.

There two types of coating we can do... I. Metal coating II. Non-metal coating

1. Electroplating 2. Hot dip galvanising 3. Aluminium coating of steel 4. Thermal spray coating 5. Chemical vapour deposition 6. Vacuum evaporation & thin film deposition

 Phosphate coatings are of porous crystalline structure and firmly bounded to the base metal.  They are produced by a complete chemical reaction taking place between free phosphoric acid, metallic phosphate salts and the metal being processed.  There are three commonly know coating are i. Iron phosphate ii. Zinc or zinc iron phosphate and iii. Manganese phosphate

 Zinc phosphate coating are widely use for steel and iron.  Second best is manganese phosphate, which are harder and darker in colour than zinc iron phosphate coating and withstand higher temperature.  They provide excellent base for paint iron phosphates are used widely as a base for paint where corrosion requirement are not rigorous.

1. Phosphate coatings 2. Chromate coatings

They give… i. Resistance to corrosion ii. Provide an ideal bonding surface for point, oil or wax application iii. for steel to provide absorbing surface for holding drawing lubricant.

The maximum use of phosphate coating is made to prepare the surface before painting over & above it is used for following application : i. As a base for oil and other corrosion resistant. ii. For lubricity and wear resistance. iii. To prepare surface for satisfactory cold forming. iv. Temporary or short time protection against corrosion. v. As a base for adhesives used for plastic-metal lamination and rubber-metal lamination.

 In chromate coating, the protective film is formed by the reaction of chromic acids or chromium salt such as sodium or potassium dichromate.  The coating is applicable to zinc, cadmium, magnesium and aluminum.  it is fast and inexpensive and suitable for large quantity. They provide excellent atmospheric corrosion protection.  The yellow-brown appearance on many hardware screws, hinges or electric hardware is because of chromate conversion coating.

FORMULA OF CHROMATE COATING MICROSCOPIC STRUCTURE OF CHROMATE COATING

 Painting  Porcelain enameling  Plastic coating

 Defination of painting The application of thin organic coating provided for the purposes of decoration, protection and functional is know as painting.

 Types of painting 1. Enamels : It is mixture of pigments is varnish or resin. Its polymerization due to oxidation occur at room temperature or after heating. 2. Lacquers : it is made up of dissolved thermoplastic materials in organic solvant. It gives or generate a film. It dries due to evaporation of solvant. Hence lacquer has a property to dryout fast on the basis of nitrocellulose and derivatives, vinylresins and acrylic resins, the lacquers are made. The lacquers can be applied on the surface by paints brush, by spraying, by tumble coating, by electro-plating & by powder coating.

The merits of paintings in comparison to other processes are as follows: i. The painting equipments are cheap & simple and need less control. ii. Cost of labour and material is less. iii. Organic coatings are available in various form, colour, smooth, glossy and surface texture. iv. The organic coating film can protect more than one corrosive environment in comparison to other metallic coatings e.g. it can provide protection against corrosion due to seat water & acid fumes.

 To improve appearance and to provide protection to the surface of cast iron, aluminum and steel sheets porcelain enameling is done. The porcelain is fired matured at a temperature of 425 degree centigrade and above, until thoroughly fused.

1. Ground coat : The ground coat contains oxides which helps enamels adherence on the surface. To improve the appearance and properties of coating. It has different colours like blue, black, brown and gray. 2. Cover coat : The cover coat enamels are applied on the layer of ground coat enamels. cover coats are clear, semi opaque and opaque. By the addition of pigments in cover coat different types of colours can be obtained.

 It is mainly used in equipment, tank of water heater, sanitary wares and cooking utensils.  It is also in processing equipment, agricultural storage tank and in parts of pumps and pipes.  The special uses of enameling are for providing chemical resistance, corrosion protection, weather resistance, for specific mechanical and electrical properties, providing good appearance & colours. For improving cleanability and for increasing thermal shock resistance.

The methods used to provide plastic coating on metal s are as follows : Dipping : a) Liquid plastisol method b) Fine powder method Depositing : a) Vacuum coating Spraying : a) Electrostatic spraying b) Flam spraying

 The coatings of polythene, nylon, C.A.B., pantone and other selected P.V.C. Are applied by dipping method, which utilies fine powder.12 mm thick layer can be developed by plastisol liquid method.

 The pantone and nylon powder is pulled by vacuum and applied on the metal in the form of coating.  The benefit of vacuum is that the air cannot enter inside the coating.

 Electrostatic Spraying : In this method powder is sprayed on metal part earthed at high voltage.  Flame Spraying : The flam spraying sprays the 60 mesh grade with spray gun uses the insert gas under pressure.

 Plastic processes a property of corrosion resistance against many corrosive environments.  Metal surface are protected against corrosion by developing plastic coating on it.  It protects the equipments of chemical plants, tank, pipeline and valve body against corrosion.

Thank you