DIFFUSION COATED FURNACE TUBES FOR THE PRODUCTION OF ETHYLENE

摘要

The inner surface of ethylene furnace tubes is diffusion coated with a suffi cient amount of chromium or chromium and silicon to form a first coating having a thickness of at least two mils. This coating is the n cleaned, neutralized, and grit blasted. Then a second coating of a sufficient amount of aluminum or aluminum and silicon is diffused onto the first coating to form a total coating thickness of a t least five mils. The surface of the second coating is cleaned and polished to remo ve the nickel and iron-rich overlay which is present as a result of the coating process and to provide a smooth uniform surface. When ethylen e is produced using furnace tubes which are coated in th is manner less coking occurs.