Method for forming a protective coating containing aluminium and zirconium on a metal part

A method for forming a protective coating containing aluminium and zirconium on a surface of a metal part, the method comprising:

• placing the part, a cement made of aluminium alloy, and granules of ZrOCl2 in a chamber;
• applying a treatment temperature to the chamber to form an atmosphere comprising an active gas which reacts with the cement to form a gaseous aluminium halide, which decomposes in contact with the part depositing metallic aluminium thereon, the active gas comprising ZrOCl2 that decomposes in contact with the part depositing Zr metal thereon, and being formed by vaporizing the granules of ZrOCl2 that are solid at ambient temperature,
• wherein during the treatment, the part, the cement, and the ZrOCl2 granules are progressively heated together, in the chamber, from ambient temperature to a temperature with a plateau at 400° C.±200° C., the heating plateau lasting 5 to 30 minutes during which the vaporized granules of ZrOCl2 are distributed in the atmosphere, and
• wherein a concentration of Zr deposited on the metal part is controlled by adjustment of a quantity of the ZrOCl2 relative to the donor cement placed in the deposition chamber, adjustment of the atmosphere of the chamber, and at least one parameter selected from the group consisting of adjustment of the temperature of the plateau and adjustment of a rate of heating the chamber from the plateau to the aluminization treatment temperature.