Angus J. M. C. Cook

Dopant Effects in Polyaniline Inhibition of Corrosion-Driven Organic Coating Cathodic Delamination on Iron

Coatings comprising various volume fractions of particulate polyaniline dispersed in a polyvinylbutyral binder are applied to iron substrates. A scanning Kelvin probe is used to measure substrate potentials in humid air and follow corrosion-driven coating delamination (cathodic disbondment) when 5% w/v (0.86 M) aqueous NaCl contacts a coating defect. Emeraldine base has no effect on substrate potential or delamination kinetics. Emeraldine salts (ES) doped using p-toluenesulfonic (HpTS), camphorsulfonic (HCS), phosphoric (H 3 PO 4 ), and phenylphosphonic (H 2 PP) acids increase substrate potentials by up to 0.36 V and inhibit delamination with efficiency order of HpTS < HCS < H 2 PO 4 << H 2 PP. Dopant salts added to the corrosive electrolyte do not inhibit delamination. It is proposed that inhibition arises primarily from cathodic O 2 reduction becoming relocated from the ennobled substrate onto the ES coating. However, Fe 3 (PO 4 ) 2 and FePP salt films formed at the ES-substrate interface also contribute by hindering interfacial electron transfer.

Corrosion control: general discussion.

[Cook, Angus; Davenport, Alison] Univ Birmingham, Birmingham B15 2TT, W Midlands, England. [Frankel, Gerald] Ohio State Univ, Columbus, OH 43210 USA. [Hughes, Trevor] Schlumberger Gould Res, Cambridge, England. [Gibbon, Simon] AkzoNobel RDI Marcus, Philippe] CNRS Chim ParisTech, Paris, France. [Lyth, Stephen] Kyushu Univ, Fukuoka 812, Japan. [Shoesmith, David; Wren, Clara] Western Univ, London, ON, Canada. [Wharton, Julian] Univ Southampton, Southampton SO9 5NH, Hants, England. [Hunt, Gregory] Lubrizol, Wickliffe, OH USA. [Lyon, Stuart; Lindsay, Rob; Morsch, Suzanne] Univ Manchester, Manchester M13 9PL, Lancs, England. [Majchrowski, Tom] Natl Nucl Lab, Workington, Cumbria, England. [Williams, Geraint] Swansea Univ, Swansea, W Glam, Wales. [Oller, Beatriz Rico; Nixon, Sonja] Airbus Grp Innovat, Ottobrunn, Germany. [Todorova, Mira] Max Planck Inst Eisenforsch GmbH, Dusseldorf, Germany. [Cheng, Su-Ting] Max Planck Inst Iron Res, Dusseldorf, Germany. [Scully, John] Univ Virginia, Charlottesville, VA 22903 USA. [Wilson, Ann] Univ W Indies, St Augustine, Trinid & Tobago. [Renner, Frank] Hasselt Univ, Inst Mat Res IMO, B-3590 Diepenbeek, Belgium. [Taylor, Christopher] DNV GL, Katy, TX USA. [Taylor, Christopher] Ohio State Univ, Columbus, OH 43210 USA. [Habazaki, Hiroki] Hokkaido Univ, Sapporo, Hokkaido 060, Japan. [Michaelides, Angelos] UCL, London, England. [Visser, Peter] Delft Univ Technol, NL-2600 AA Delft, Netherlands. [Kyhl, Line] Aarhus Univ, DK-8000 Aarhus C, Denmark. [Kokalj, Anton] Jozef Stefan Inst, Ljubljana, Slovenia.

In Situ Synchrotron X-Ray Diffraction Characterization of Corrosion Products of a Ti-Based Metallic Glass for Implant Applications

Ti-based bulk metallic glasses are under consideration for implants due to their high yield strength and biocompatibility. In this work, in situ synchrotron X-ray diffraction (XRD) is used to investigate the corrosion products formed from corrosion of Ti40 Zr10 Cu34 Pd14 Sn2 bulk metallic glass in artificial corrosion pits in physiological saline (NaCl). It is found that Pd nanoparticles form in the interior of the pits during electrochemical dissolution. At a low pit growth potential, the change in lattice parameter of the Pd nanoparticles is consistent with the formation of palladium hydride. In addition, a salt layer very close to the dissolving interface is found to contain CuCl, PdCl2 , ZrOCl2 ∙8H2 O, Cu, Cu2 O, and several unidentified phases. The formation of Pd nanoparticles (16 ± 10 nm at 0.7 V vs Ag/AgCl) containing small amounts of the other alloying elements is confirmed by transmission electron microscopy. The addition of albumin and/or H2 O2 does not significantly influence the nature of the corrosion products. When considering the biological compatibility of the alloy, the biological reactivity of the corrosion products identified should be explored.