An Electrochemical Investigation into the Corrosion Protection Properties of Coatings for the Active Metal Copper


Carragher, Ursula (2013) An Electrochemical Investigation into the Corrosion Protection Properties of Coatings for the Active Metal Copper. PhD thesis, National University of Ireland Maynooth.

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Abstract

In the research presented in this thesis, corrosion protection films were synthesised and characterised. The films were based on polypyrrole (PPy) coatings doped with combinations of tartrate, oxalate and dodecylbenzene sulfonate (DBS) along with the incorporation of multiwalled carbon nanotubes (MWCNT), and viologen films adsorbed at copper. The corrosion protective properties of these films were studied and compared to the uncoated copper substrate. They were assessed and studied using a combination of cyclic voltammetry, polarisation curves, Tafel analysis, open-circuit potential measurements and electrochemical impedance spectroscopy. Polypyrrole films were successfully deposited at copper from a 0.10 mol dm-3 oxalate solution at a pH of 8.0 and a 0.10 mol dm-3 tartrate solution at a pH of 7.0 to generate PPy- Tartrate and PPy-Oxalate films on copper. SEM micrographs confirmed that the polymers were homogeneous, defect and crack-free. In addition, bi-layers comprising PPy-Tartrate/PPy- Oxalate and PPy-Oxalate/PPy-Tartrate were successfully formed at the copper interface. The bi-layer provided the better corrosion protective coatings. Higher breakdown potentials were observed with the bi-layer. In an attempt to further improve the corrosion protective properties of the bi-layer coatings, MWCNT, were incorporated into the polymer films. The MWCNT were successfully dispersed using DBS. The concentration ratio of the MWCNT to DBS was important in forming a stable and well dispersed solution. This was achieved using 0.05 mol dm-3 DBS and 0.02 mg MWCNT. The MWCNT-modified polypyrrole films were deposited as bi-layers and multi-layers and showed excellent corrosion protection for copper. The PPy- Tartrate/PPy-DBS bi-layer films also showed potential as a corrosion protective coating. An alternative approach was then considered. The electrochemical deposition of three viologens, methyl viologen (MV), benzyl viologen (BV) and ethyl viologen (EV) at copper in the presence of a 0.10 mol dm-3 NaCl supporting electrolyte was studied. The formation of the viologen films was achieved by cycling the copper electrode from -0.20 to 1.00 V vs. SCE at a scan rate of 1 mV s-1. For comparison, the copper was cycled under the same conditions in the 0.10 mol dm-3 NaCl solution, but in the absence of the viologens. Significant dissolution of the copper was observed in the absence of the viologens. However, considerably lower currents were measured in the presence of the viologens, indicating a reduction in the rate of dissolution and the formation of a protective film.

Item Type: Thesis (PhD)
Keywords: Electrochemical Investigation; Corrosion Protection Properties; Active Metal Copper;
Academic Unit: Faculty of Science and Engineering > Chemistry
Item ID: 4326
Depositing User: IR eTheses
Date Deposited: 19 Apr 2013 11:39
URI:

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