ANS:B - hot dipping

Tin-plated iron and galvanized iron are generally produced by hot dipping. Hot dipping is a method used to coat iron or steel surfaces with a layer of another metal to provide protection against corrosion or to enhance certain properties. In the case of tin-plated iron and galvanized iron:

1. Tin-plated iron: In tin plating, the iron or steel substrate is immersed in a bath of molten tin. The metal surface is thoroughly cleaned and then dipped into the molten tin, allowing the tin to adhere to the surface. The tin coating provides corrosion resistance and improves the appearance of the iron or steel substrate.
2. Galvanized iron: In galvanizing, the iron or steel substrate is immersed in a bath of molten zinc. The metal surface is cleaned and then dipped into the molten zinc, where a metallurgical bond forms between the zinc and the iron or steel substrate. The zinc coating acts as a sacrificial anode, protecting the iron or steel from corrosion by forming a protective barrier.

Electroplating involves the deposition of a metal coating onto a substrate using an electric current, and spraying typically refers to the application of a coating using a spray gun. These methods are not commonly used for producing tin-plated iron or galvanized iron.