French Pressurised Water Nuclear Reactors have steam generators made of Inconel 690, a nickel-base superalloy with high chromium and iron contents. Corrosion of this superalloy in primary water conditions may be reduced by a surface treatment of the tubes. The deposition of chromium onto Inconel 690 in cementation packs containing a chromizing mixture and a CrCl3 activator is studied between 1273 K and 1523 K in sealed quartz tubes. At constant volume, liquid CrCl2 is synthesised in the conditions used. Two layers are observed at 1273 K and 1323 K by metallographic observations. The composition of the outer layer is a thick alpha Cr-rich layer with 4.6 at% Ni and 1.7 at.% Fe. An inner diffusion layer also grows. It corresponds to a gamma -Cr-Ni layer. At 1523 K, only the Cr-rich layer still grows and Kirkendall porosity appears. Growth rates of the Cr-rich layer are parabolic whatever the temperature. The rate-limiting step is very likely diffusion of chromium into the chromium-rich layer. Finally, oxidation tests were carried out in a loop simulating primary water conditions of Pressurized Water Reactor.