Draw diagram and explain sherardizing process
Process: i) The iron articles (bolts, screws, nails etc) to be coated are first cleaned and then packed with Zn dust and ZnO powder in a steel drum, which is provided with electrical heating arrangement. ii) The drum is slowly rotated for 2-3 hours and its temp. is kept between 350 400o C. iii) During this process Zn gets diffused slowly into iron forming Fe - Zn alloy at the surface which protects iron surface from corrosion. It is used for protecting small steel articles like bolts, screws, nuts, threaded parts, washers, valves, gauge, tools etc.