The present invention relates to synthesizing reduced graphene oxide on the surface of a metal sheet and glass. The invention particularly relates to a process for coating a substrate with reduced graphene oxide using seedlac as a carbon source. As per the process of the current invention, a solution of seedlac is prepared in an alcohol and the substrate is dipped in to the solution for one or more time. The substrate is then dried in air for 1-10 minutes and thereafter, heated to a temperature range of 400 to 1200 DEG C under controlled atmosphere of Ar/N2/Ar-H2/N2-H2 at a different flow rate ranging from 100 to 500 sccm for a period of 10 to 120 minutes.