The codeposition of Cr and Al into Ni substrate has been achieved using the single-step pack cementation process. The effect of activators, temperature and the activity of Cr and Al in the Cr-Al masteralloys on the formation of Ni-Cr-Al coatings and concentration control of Cr and Al was investigated in an argon atmosphere at 1273K and 1373K. The coatings consisted of an outward-grown β-NiAl layer in which Cr was dissolved except for the coating formed by 5wt%Al-1273K coating condition where Cr and Al dissolved in Ni substrate. Aluminide coatings grown outwards in pack powders were embedded with Al₂O₃ and masteralloy particles and Kirkendall voids were formed in Ni beneath the coating-substrate interface. A masteralloy of high Cr/Al activity ratio, low coating temperature and less stable activator are essential for codeposition of Cr-Al and provision of microstructures and composition which promise good oxidation/corrosion resistance to Ni-Cr-Al coatings.