B. Wessling, S. Schröder, S. Gleeson, H. Merkle, S. Schröder, F. Baron

Reaction scheme for the passivation of metals by polyaniline

Materials and Corrosion 47 (1996) 439-445

Using UV-VIS spectroscopy and elemental analysis following the reaction which occur between PAni and steel, it was possible to clarify the passivation reaction responsible for the amazing corrosion protection performance of PAni*. A reaction scheme is presented.

improved version as of Dec 96

This means that PAni is oxidizing iron to Fe²⁺ where it is itself reduced to Leucoemeraldine. Further oxidation of the iron ions leads to Fe2O3**, and oxygen is re-oxidizing the Leuco form of PAni to the emeraldine salt. This tells us that the full mechanism of the corrosion protection consists of

- potential shift due to the noble metal properties of PAni *

- and the redox catalytic properties of PAni leading to the passivating oxide layer

* B. Wessling, Adv. Mater. 6 (1994), 226

** W.-K. Lu, R. Elsenbaumer, B. Wessling
Synth. Met. 71 (1995), 2163 - 2166

further informations:
the passivation mechanism of polyaniline on metals is revealed
industrial applications