Prevention of biofilm growth on surfaces immersed in an aqueous environment could be obtained either by the release of an antifouling biocide or by the presence of such compounds on the surface. In this paper it is shown, for the first time, that an electrochemical treatment performed in the presence of chlorides and proteins allows the immobilization of an organic biocide (chloramine) on the electrode. This electrode is a stable transparent conductive tin dioxide film coated on glass. It is polarized to oxidize chloride ions into hypochlorous acid, which reacts with the organic matter (bovine serum albumin) present at the electrode/solution interface, leading on one hand to the chlorination of the proteins with in particular the chloramine formation and on the other hand to the protein aggregation on the surface.