Recently, by increasing turbine engine temperature, traditional pack cementation method is not successfully applied on blades with cooling system and complex shapes. Gas phase aluminizing is a useful method that can be used instead to form an aluminide layer on the surfaces of the samples. It seems that applying a MCrAlY bond coat by HVOF thermal spray technique between aluminide top layer and the substrate is desired to protect the substrate from environmental hot corrosion attacks. In this study, hot corrosion behavior of these coatings applied on IN718 is investigated and compared to the MCrAlY coatings and aluminide coatings in the case they’re applied on the superalloy IN718 individually and bare superalloy. Hot corrosion test done by deposition of Na 2 SO 4 -25%Wt K 2 SO 4 salts on the surface of samples and remaining in 900? C for 120 hrs. Results showed that bare alloy samples had a significant weight lose and hard attacks on the surface, however coated samples showed better hot corrosion resistance. High value diffusion of Fe into the aluminide coating from substrate and consequently forming porous Fe rich oxides is the reason of less hot corrosion resistance of simple aluminide layer than other coated samples. CoNiCrAlY coated samples formed a thin alumina oxide layer on the surface that spalled by Al depletion of CoNiCrAlY after 120 hr hot corrosion test. Samples with aluminide/CoNiCrAlY coatings showed excellent hot corrosion resistance in the test conditions than other samples. These coatings by having more than 30 %wt Al in their chemical composition formed a dense and continueous Al 2 O 3 cale and protected the sub layers from the severe environmental attacks. These samples remained resistant even after 120 hr hot corrosion test. Spallation mechanisms of the samples in comparison to high hot corrosion resistance of aluminide/CoNiCrAlY coatings are discussed. Key words : Ni-base superalloy, hot corrosion, aluminide coating, CoNiCrAlY, gas phase aluminizing, HVOF thermal spray. .