Abstract: A method of treating a substrate, the method comprising: delivering substantially simultaneously a first set of particles comprising a dopant and a second set of particles comprising an abrasive from at least one fluid jet to a surface of the substrate, to impregnate the surface of the substrate with the dopant; wherein the dopant comprises a corrosion-inhibiting or adhesion-promoting species, such as to form a corrosion-inhibiting or adhesion-promoting coating at or on the surface of the substrate. Also provided is an article comprising a substrate having a corrosion-inhibiting or adhesion-promoting coating, the said coating comprising particles of a corrosion-inhibiting or adhesion-promoting species that impregnate the surface of the substrate (e.g. as produced by the above method).