Why do we apply oil on iron tools kept in storage

Q. Give reasons:
a) Why is pure gold not suitable for making ornaments?
b) Why calcium is found in the form of compound?
c) Why electrical wires are coated with PVC (Poly Vinyl Chloride)?
d) Why do we apply oil on iron tools kept in storage?
e) Why sodium is stored in kerosene oil?

Q. Why do we apply paint on iron articles?

Q. Why do we apply paints on iron goods?

Q. Assertion :Polished iron nails do not rust when kept immersed in a test tube containing boil water covered with a layer of oil. Reason: Rust formation can be controlled with coatings such as paint or varnish that isolate the iron from environment. When only temporary protection is needed for storage or transport a thin layer of oil, grease can be applied to an iron surface.