Question

Iron does not rust even if the zinc coating is broken in a galvanized iron pipe.Give reasons. 

Answer 1

1. Anodic coating type of coating protect base metal “sacrificially”. Corrosion ofiron does not enhance even on breaking “anodic coating” as it heals its film.
2. The iron, coating metal is at lower electrode potential than zinc base metal.
3. Galvanizing is a process of coating iron with thin coat of zinc to protect themfrom rusting.
4. The iron sheets are cleaned with dilute H2SO4 i.e. pickling to removeimpurities. In this process, NH4Cl flux is used.
5. Molten zinc is maintained at 425-4300C and it becomes the reason of iron andrusting even of zinc coating is broken in a galvanized iron pipe.