The grafting of 4-nitrophenyl groups on carbon or metallic surfaces without externally applied electrochemical induction is described. Clean surfaces of glassy carbon (GC), copper, nickel, iron, and zinc substrates were dipped in a solution of 4-nitrobenzene diazonium tetrafluoroborate salt in acetonitrile. After the modified surfaces were rinsed, they were analyzed by FT-IRRAS, cyclic voltammetry, XPS, and AFM. The main result of this investigation is the spontaneous formation of a multilayer coating without electrochemical induction regardless of the substrate used. Influence of immersion time and of 4-nitrobenzene diazonium tetrafluoroborate salt concentration on the grafting were also investigated.

The reduction of diazonium salts in an aprotic medium permits the attachment of substituted aryl groups to a variety of metals: Co, Ni, Cu, Zn, Pt, and Au. These aryl groups are strongly bonded to the metal as they resist sustained rinsing under sonication in organic solvents. The organic layers have been characterized by cyclic voltammetry, infrared reflection absorption spectroscopy, X-ray photoelectron spectroscopy, Rutherford backscattering, electrochemical impedance spectroscopy, and atomic force microscopy. From these data it is possible to propose a structure for these grafted layers.

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Electrochemical reduction of aryldiazonium salts on an iron electrode in acetonitrile leads to the attachment of aryl groups to the iron surface. We investigated aryl groups substituted with 4-alkyl chains (−CH3, −C4H9, −C12H25, −OC12H25, −OC16H33), with 4-halogeno substituents (−I, −F, −CF3, −OCF3, or −C6F13), or with five fluorine atoms (pentafluoro phenyl, −C6F5). Attachment of these groups was characterized by FTIR, XPS, and capacity measurements. It is shown by measuring the polarization resistance and the corrosion current that these layers provide a significant protection against corrosion.

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