Abstract: A diffuser of a rotating fluid machine that processes a gas with high level of contaminants is provided, the diffuser having an annular surface portion facing rotating vanes of a rotor of the rotating fluid machine, the annular surface portion being at least partially covered with an abradable and anti-encrustation coating including (A) a first lower metal-based coating layer applied on the annular surface portion of the diffuser, and (B) a second upper polymer-based coating layer applied on the first lower metal-based coating layer, wherein the first lower metal-based coating layer comprises 99% by weight of aluminum powder based on the total weight of the first lower-based coating layer and is anchored to the annular surface with a nickel and aluminum (NiAl) binder.

Abstract: An abradable and anti-encrustation coating is described for a rotating fluid machine (10) of the type comprising a casing (12), in which a shaft (14) equipped with at least one rotor (16) having a series of circumferential vanes (18) is rotatingly assembled and at least one diffuser (20) integral with the casing (12). The outer edge of each circumferential vane (18) faces an annular surface portion (28) of the diffuser (20). The annular surface portion (28) of the diffuser (20) is at least partially covered with a coating which can be abraded by the outer edge of each circumferential vane (18), said abradable coating comprising of a first lower metal-based coating layer (30), applied on the annular surface portion (28) of the diffuser (20), and a second upper polymer-based coating layer (32), applied on the first lower metal-based coating layer (30).