Metal objects are treated by anodising the metal object in contact with an aqueous electrolyte, and then subjecting the anodised metal object to a reversed voltage. The anodising is performed in two stages, firstly to passivate with the formation of an oxide layer, and secondly to form regions in the oxide layer having a higher oxygen to metal atom ratio, for example pits or caps, in this oxide layer. The second stage of anodising is performed by applying a multiplicity of voltage cycles, each voltage cycle involving ramping the voltage between a lower threshold voltage and an upper threshold voltage, and then returning to the lower threshold voltage. The reversed voltage step forms a hydrous metal oxide in the regions of higher oxygen to metal atom ratio, and the oxide layer and hydrous metal oxide together constitute a surface layer which is integral with the metal object, and has ion exchange capacity. After the reversed voltage step the metal object is then contacted with a bio-effective material such as a biocidal metal, which is absorbed into the surface of the metal object. The processing time may be reduced by applying the multiple voltage cycles. The invention also provides a treated metal object which can be prepared by treating a metal object having a micro-rough surface according to the method described above.L'invention concerne des objets métalliques traités par anodisation de l'objet métallique en contact avec un électrolyte aqueux, puis en soumettant l'objet métallique anodisé à une tension inverse. L'anodisation est effectuée en deux étapes, en premier lieu, la passivation avec formation d'une couche d'oxyde, et, en second lieu, la formation de régions dans la couche d'oxyde présentant un rapport entre oxygène et atomes métalliques plus élevé, par exemple des creux ou des sommets, dans cette couche d'oxyde. La seconde étape d'anodisation est effectuée par application d'une multiplicité de cycles de tension, chaque cycle de tension entraînant une aug
