Question

what makes metal dull after sometime​

Answer 1

Answer:

the metal loses its metallic lustre after sometime due to its reaction with atmospheric oxygen. so it becomes dull.

this does not happen in every metal example gold it is difficult to form oxides with reaction with air.

hope this helps.

Answer 2

Answer:

When we are buying metals, it may have shiny appearance.

But when this metal come in contact with atmosphere and moisture it losrs its lustrous appearance