It is a natural process that occurs when pure metals react with things such as water or air, causing them to change into undesirable chemicals.
The slow action of various gases present in the air generates a thin coating of oxide, carbonate, or sulfide on the surface of metals exposed to the air for a long period of time.
Due to corrosion metals lose their shine and color.
For preventing corrosion on metals we can do electroplating, galvanization, painting, etc.
Therefore, lead loses its luster due to corrosion.