Question

why are brass cooking vessels coated with tin?

Answer 1

Brass and copper utensils are coated with tin so they do not get corroded when exposed to atmosphere. Brass and copper utensils are coated with tin so that they donot get oxidised and rusted.

Answer 2

Brass cooking vessels usually get corroded due to a greenish layer that forms on the surface.
To prevent this, brass vessels are given a coating of tin to prevent all such damages and to protect the vessel

Hope that helps!