Question

geetha observed a brownish layer on windows and railings of her house. what is the reason behind it? how do you prevent it? give some suggestions?

Answer 1

it's due to rusting as iron in presence of oxygen and moist air starts forming rust which is basic in nature.
prevention:
by painting
by galvanising
by freezing

I think it would be enough for your question

Answer 2

This brownish layer is due the rusting of iron.This caused due to moisture of iron and presence of other gases.

Prevention:

It can be prevented by painting