NiCoCrAlY coatings were prepared on superalloy K417G using arc ion plating (AIP), then some specimens coated with NiCoCrAlY were aluminized using a pack cementation method. The high temperature oxidation and hot corrosion behavior of the ordinary and the aluminized NiCoCrAlY coatings were studied. The results indicated that α-Al 2 O 3 scales grew on both coatings during oxidation at 1000°C and 1100°C in air, and the aluminized NiCoCrAlY coating always showed lower oxidation rates and lower degradation rates. The hot corrosion tests were carried out by applying salt films of 25wt.% K 2 SO 4 +75wt.% Na 2 SO 4 mixture on the specimens and exposing in air at 900°C. The aluminized NiCoCrAlY coating showed a longer lifetime by forming a continuous Al 2 O 3 scale. But, cracks and spallation of the oxide scales occurred on the ordinary NiCoCrAlY coating after 80h.