Thermal cracking of hydrocarbons is one of the most important processes in petrochemical plants which results in the production of olefins, especially ethylene and propylene, as desirable products. Contrariwise, coke is an undesirable product that is deposited on the internal wall of cracking tubes. Deposited coke increases pressure and fuel consumption, reduces heat transfer and also the lifetime of tubes. Among other destructive phenomena happening in the cracking tubes, carburization and high temperature oxidation could be noted. In this work, to improve anti-coking behavior and also resistance to oxidation and carburization of HP-micro steel, aluminide coatings were applied. XRD test results showed Al 0.96 Ni 1.04 and AlNi phases for Al-10 and Al-30 samples, respectively. After carburization test, the bare sample was severely carburized accompanied by increasing the hardness. In contrast, Al-10 and Al-30 samples showed high resistance to carburization. After coking test, FESEM images depicted much catalytic coke on the surface of bare sample and less on the Al-10 sample, but often spherical coke from gaseous reaction on Al-30 sample. Anti-coking ratio for Al-10 and Al-30 samples was %63 and %80, respectively. After oxidation test, thickness of oxide layer was 22, 14 and 6 µm for bare, Al-10 and Al-30, respectively. Parabolic rate constant (k p ) of bare sample was 13.87, which was higher than of coated samples in all time periods. Also, the slope of the curve of (?W/A) 2 vs. time for coated samples decreased over time, due to gradual converting of ?-Al 2 O 3 to ?-Al 2 O 3 . Overall, Al-30 aluminide coating was more able to protect the surface against oxidation and other destructive phenomena.
