X-ray photo-electron spectroscopy is used to examine the adsorption of benzotriazole on copper and copper alloys. The nature of the film is dis cussed. It is concluded that formation of a Cu(I)BTA surface complex occurs which on removal from the liquid phase is rapidly oxidised to a Cu(II) complex. The presence of Cu₂O is observed to facilitate formation of the surface film. For brass it is concluded that zinc participates in formation of the surface complex. -- AATA