Iron metal is largely used for making ships. ln the sea, ship is in contact with saline water. Destruction of iron becomes quicker in saline medium. a)What is such processes generalty called? b). Destruction of iron can be prevented by coating with zinc, Explain the chemical reaction by-which iron gets protected. Give equations.

Explanation

a: Rusting or corrosion.
b. Saline medium hạs extra salts, suchias sodium,chloride in water. This means it has a "greater.concentration of eléctrolyte than or.dinary medium. The ions present will favour the formation of more electrochienićal cells and will thus-promote rusting, or corrosion. `Zn(E^a zn^2- / zn=-0.76 ~V)` is more électroposi-
tive than iron `(E^circ Fe^2+ / Fe=-0.44 ~V), so`
zinc possesses greater teindency to lose electrons than iron. Thus. zinc protects iron form rusting at its own cost. Consequently. If by reason.the protective.layer of zinc is , scratched, atmospheric air and modisture dissolve zinc and rot fron. Thus zinc acts, as the anodic region, whịe iron as the sathodic region. `Zn Zn^2++2 e` (anodic region)
`H_2 O H^*+OH^2`