Method of doping surfaces

A method of treating a surface of an object, wherein the object is a metallic article, the method comprising: administering substantially simultaneously a first set of particles comprising a dopant (6) and a second set of particles comprising an abrasive (4) from at least one fluid jet (2) to a surface (10) of the object, to impregnate the surface of the object with the dopant (6); wherein the method further comprises removing a metal oxide from the surface of the metal substrate to expose a metal surface, cleaning abrasively by shot blasting the metal oxide with the second set of particles substantially simultaneously with administration of the first set of particles .