Ennore is situated in the northern part of Chennai city at the east coast of South India near Bay of Bengal. Thermal power plants, petrochemical plants, ports, refineries, pharmaceutical companies and residential buildings are situated in Ennore and it is a marine-industrial-urban environment. There are no reports on the detailed field study of rust layers formed on weathering steels subjected to long term exposure in an industrial-marine-urban environment in India. In the present investigation, thermo gravimetric analysis and N2 adsorption studies were used to understand the nature of corrosion products formed on the skyward and earthward rust layers of weathering steel exposed at Ennore, Chennai, India