Question

Describe the tinning process. Write its two applications.

Answer 1

Tinning: -The process of covering iron or steel sheets with a thin coat of tin to prevent it from rusting is called as tinning.

 

Process: i) The sheet of steel to be protected is first cleaned by dilute H2SO4 acid to remove any oxide film and impurities. ii) After this it is passed through a bath of molten flux of ZnCl2 which helps the molten metal to get adhered to the metal sheet. iii) Then sheet of steel passes through a tank of molten tin. iv) Finally it is dipped in a suitable vegetable oil like palm oil to protect the hot tin coated surface against oxidation. v)Then sheet is passed through a series of hot rollers to remove any excess of tin, and make the coating uniform all over the surface of metal sheet.

Applications of tinning process: i) Tinning is used in manufacturing various types of cans for storing food stuff biscuit tins, kitchen utensils, oil, ghee, pickles, medicines, kerosene etc. because tin protects the metal from corrosion and avoids food poisoning. ii) Tin plated sheets are used for making trunks, boxes, for roofing, for vessels of storing petroleum etc. iii) Copper wire to be insulated with rubber is first tinned to protect it from sulpher attack of the rubber. iv) Tinned copper sheets are used for cooking utensils and refrigeration equipment. Cu tubes are used in refrigeration.