Direct Electrodeposition of Polypyrrole on Aluminum and Aluminum Alloy by Electron Transfer Mediation

Abstract

The direct electrodeposition of electroactive conducting polymers on active metals such as iron and aluminum is complicated by the concomitant metal oxidation that occurs at the positive potentials required for polymer formation. In the case of aluminum and its alloys, the oxide layer that forms is an insulator that blocks electron transfer and impedes polymer formation and deposition. As a result, only patchy nonuniform polymer films are obtained. Electron transfer mediation is a well-known technique for overcoming kinetic limitations of electron transfer at metal electrodes. In this work, we report the use of electron transfer mediation for the direct electrodeposition of polypyrrole onto aluminum and onto Al 2024-T3 alloy. This report focuses on the use of Tiron (4,5-dihydroxy-1,3-benzenedisulfonic acid disodium salt) as the mediator, although catechol appears to function in a similar manner. Depositions were carried out under galvanostatic conditions at current densities of 1 normalmA/cm2. The mediator reduced the deposition potential by nearly 500 mV compared to deposition performed in the absence of mediator (where Tiron was replaced by p-toluene sulfonic acid sodium salt). Polypyrrole formation and deposition appears to occur with 100% current efficiency and uniform films are obtained. Results of the characterization of these films by scanning electron microscopy, atomic force microscopy, X-ray photoelectron spectroscopy, conductivity measurements, and adhesion measurements are presented. © 2002 The Electrochemical Society. All rights reserved.

Polypyrrole Coating on Zinc for Corrosion Prevention of Zinc-coated Steels

“…Other authors also presented the corrosion prevention of stainless steel by PANI coating [2][3][4] as well as PPy coating. 5,6) Since the conducting polymer coatings could be electrochemically formed on various metals, 7,8) they were applied to corrosion prevention of the metals of Cu, 9) Zn, 10) Al, 11) Ti, 12) CuNi. 13) As zinc is one of less noble metals, the oxidative PPy formation may not be easy, because the electrochemical oxidation induces anodic dissolution of zinc before the PPy formation.…”

The electrochemical deposition of polyaniline at pure aluminium: electrochemical activity and corrosion protection properties

“…For example, Tallman et al [8] have electrodeposited polypyrrole at aluminium and an Al2024-T3 alloy using 4,5-dihydroxy-1,3-benzenedisulfonic acid di-sodium salt as a mediator to overcome kinetic limitations of the electron transfer at the insulating aluminium oxide surface. The mediator was found to reduce the deposition potential by nearly 500 mV compared with that found in the absence of the mediator.…”

Thin black layers on aluminum substrate—electrochemical synthesis and characterization

“…The mediator facilitates both nucleation and growth processes involved in the mechanism. [14,15] In the case of PPy electropolymerization onto the previously anodized Al, Tiron served as both mediator and dopant anion. It has lowered the deposition potential by nearly 500-700 mV compared with the deposition in the absence of mediator.…”