Systems and methods for treating a component of an installed and assembled gas turbine engine are provided. Accordingly, the method includes operably coupling a delivery assembly to an annular inlet of a core gas turbine engine. A portion of treating fluid is atomized with the delivery assembly to develop a treating mist having a plurality of atomized droplets. The atomized droplets are suspended within any path of the core gas turbine engine from the annular inlet to an axial position downstream of a compressor of the core gas turbine engine. A portion of the treating mist is impacted or precipitated onto the component so as to wet the component, and a portion of the deposits on the component is dissolved by the treating mist.