Dennis E. Tallman
Our research is in the general area of electrochemical science, with particular interests in analytical and physical electrochemistry and the science of materials and interfaces. Previous work has focused on the theory and application of microelectrodes, electrodes which have at least one dimension on the order of micrometers or smaller. Microelectrodes make possible a number of electrochemical measurements that are difficult or impossible with conventional electrodes (of millimeter dimension). For example, a microelectrode can be used to perform voltammetry in a highly resistive medium such as a supercritical fluid. Microelectrodes also display enhanced mass transfer on the typical electrochemical time scale, a feature which can be exploited in the design of electrochemical sensors having improved sensitivity. Microelectrodes having a high perimeter (edge)-to-area ratio (for example, microband or microring electrodes) are particularly useful in this regard, since current density increases as the perimeter-to-area ratio increases. Electrically conducting composite materials fabricated by incorporating a conducting powder (e.g., graphite, silver, gold, or platinum) into an insulating polymer matrix (e.g., poly(chlorotrifluoroethylene) or PCTFE) represent a highly versatile approach to microelectrode ensemble fabrication and design. Bulk modifiers which enhance selectivity or sensitivity toward a target species may be incorporated directly into the composite material. Such composites based on PCTFE are chemically and mechanically robust, machinable, and typically contain only ca. 10% conductor by volume.
More recently, our work has focused on the electrochemistry of corrosion, with four main goals: 1) investigation of active coatings for corrosion control; 2) understanding corrosion mechanisms, particularly at metal substrate/coating interfaces; 3) development of sensors for early detection of coating failure and/or corrosion onset; and 4) probing electrical and electrochemical properties of metal alloy surfaces. This work, in collaboration with Professor Gordon Bierwagen of the Coatings and Polymeric Materials Department, utilizes a variety of techniques to study corrosion and the mechanisms by which active coatings alter the corrosion behavior. We define active coatings as coatings that consist of (or contain) components that interact electrically and/or electrochemically with the active metal to be protected (e.g., Fe or Al alloys). Examples of active coatings studied in our laboratory include conjugated polymer coatings and magnesium-rich coatings for the protection of Al alloys.
Among the techniques currently used in our laboratory for the study of corrosion at coated metal substrates are global techniques (such as electrochemical noise measurements and electrochemical impedance spectroscopy) as well as a variety of scanning probe techniques that provide spatial (or local) as well as temporal information about the corrosion process. These scanning probe techniques include the scanning vibrating electrode technique (SVET, for current density mapping), the scanning ion electrode technique (SIET, especially for pH mapping), the scanning polarographic electrode technique (SPET, for oxygen mapping), local electrochemical impedance spectroscopy/mapping (LEIS/LEIM), scanning electrochemical microscopy (SECM, for probing electron transfer at surfaces), electrochemical atomic force microscopy (AFM and ECAFM) and conducting or current sensing AFM (C-AFM, for studying the conductivity of materials at the micrometer and nanometer scale). Studies using these scanning probe techniques are complemented by measurements employing scanning electron microscopy (SEM, combined with energy dispersive x-ray analysis) and x-ray photoelectron spectroscopy (XPS). Together, these techniques provide a rather complete view of the corrosion process and the manner in which it is altered by active corrosion control coatings.
Figure 1. Left - a scanning vibrating electrode (SVET) instrument, showing control computer, monitors, electronics rack and air table containing micropositioner, cell and video microscope. Right – a current density map for an aluminum alloy (AA 2024-T3) at 20 minutes immersion in dilute Harrison’s solution (0.35% (NH4)2SO4 and 0.05% NaCl) showing local anodic (positive) and cathodic (negative) currents.
Figure 2. Left - a scanning electrochemical microscope (SECM) instrument, showing control electronics, micropositioner, cell and video microscope. Right – a SECM map showing an active region for reduction on AA 2024-T3 using 0.01 M hydroquinone as mediator (in 1.0 M Na2SO4, 0.005 M H2SO4; Eprobe = 1 V, Esubstrate = open circuit potential).
J.M. Gustavsson, P.C. Innis, J. He, G.G. Wallace and D.E. Tallman, “Processible Polyaniline-HCSA/poly(Vinyl Acetate-co-Butyl Acrylate) Corrosion Protection Coatings for AA2024-T3: A SVET and Raman study,” Electrochimica Acta 54(5) (2009) 1483-1490.
Kerry N. Allahar, Brian Hinderliter, Dennis E. Tallman and Gordon P. Bierwagen, “Army Vehicle Primer Properties During Wet-Dry Cycling,” Corrosion 65(2) (2009) 126-135.
Hong Xu, Dante Battocchi, Dennis Tallman and Gordon Bierwagen, “The Use of Mg Alloys as Pigments in Mg-rich Primers for Protecting Al Alloys,” Corrosion 65(5) (2009) 318-325.
M. C. Yan, J. He, D. E. Tallman, S. C. Rasmussen, and G. P. Bierwagen, “Neutral and n-Doped Conjugated Polymers for Corrosion Control of Aluminum Alloys,” ECS Transactions 16(52) (2009) 183-194.
B. E. Merten, D. Battocchi, D. E. Tallman and G. P. Bierwagen, “Embedded Reference Electrode for Potential-Monitoring of Cathodic Protective Systems,” ECS Transactions 19(29) (2009) 223-232.
M. C. Yan, J. He, D. E. Tallman, S. C. Rasmussen, and G. P. Bierwagen, “Corrosion Control Coatings for Aluminum Alloys Based on Neutral and n-Doped Conjugated Polymers,” Journal of the Electrochemical Society 156 (2009) C360-C366.
K. N. Allahar, D. Battocchi, G. P. Bierwagen and D. E. Tallman, “Thermal Degradation of a Mg-Rich Primer on AA 2024-T3,” ECS Transactions 19(29) (2009) 75-89.
Christopher L. Heth, Dennis E. Tallman, and Seth C. Rasmussen, “Electrochemical Study of 3-(N-alkylamino)thiophenes: Experimental and Theoretical Insights into an Unique Mechanism of Oxidative Polymerization,” Journal of Physical Chemistry B 114(16) (2010) 5275-5282.
Kerry Allahar, Dante Battocchi, Gordon Bierwagen, and Dennis Tallman, "Transmission line modeling of EIS data for a Mg-rich primer on AA 2024-T3," Journal of the Electrochemical Society 157(3) (2010) C95-C101.
Maocheng Yan, Victoria J. Gelling, Brian R. Hinderliter, Dante Battocchi, Dennis E. Tallman and Gordon P. Bierwagen, “SVET Method for Characterizing Anti-Corrosion Performance of Metal-Rich Coatings,” Corrosion Science 52(8) (2010) 2636-2642.
Bobbi E. Merten, Dante Battocchi, Dennis E. Tallman, and Gordon P. Bierwagen, “Embedded Reference Electrode for Potential-Monitoring of Cathodic Protective Systems,” Journal of the Electrochemical Society 157(7) (2010) C244-C247.
J. Nie, M. C. Yan, J. Wang, D. E. Tallman, D. Battocchi and G. P. Bierwagen, “Cathodic Corrosion Protection Performance of Mg-Rich Primers: Effect of Pigment Shape and Pigment Volume Concentration,” ECS Transactions 24 (2010) 261-275.
Dennis E. Tallman, “Microelectrodes for Voltammetry - A Personal Historical Perspective,” Journal of Solid State Electrochemistry 15 (2011) 1703-1710.
Qixin Zhou, Yechun Wang, Dennis E. Tallman and Mark B. Jensen, “Simulation of SECM Approach Curves for Heterogeneous Metal Surfaces,” Journal of the Electrochemical Society 159(7) (2012) H644-H649.
Mark B. Jensen, Jake M. Karels, Jake M., Patrick J. Cool, Audrey F. Guerard and Dennis E. Tallman, “Scanning Electrochemical Microscopy and Video Microscopy Investigations of Tiron-Mediated Polypyrrole Nucleation on AA2024-T3,” Journal of Solid State Electrochemistry 16(10) (2012) 3363-3370.
Mark B. Jensen and Dennis E. Tallman, “Application of SECM to Corrosion Studies,” Electroanalytical Chemistry 24 (2012) 171-286.
Dennis E. Tallman and Mark B. Jensen, “Applications of Scanning Electrochemical Microscopy in Corrosion Research,” in Scanning Electrochemical Microscopy (2nd Edition), Edited by Allen J. Bard and Michael V. Mirkin (2013) 451-488.
Mark B. Jensen and Dennis E. Tallman, “A LabVIEW-Based Virtual Instrument for Simulation and Analysis of SECM Approach Curves,” Journal of Solid State Electrochemistry 17(12) (2013) 2999-3003.
Sina S. Jamali, Simon E. Moulton, Dennis E. Tallman, Maria Forsyth, Jan Weber and Gordon G. Wallace, “Applications of Scanning Electrochemical Microscopy (SECM) for Local Characterization of AZ31 Surface During Corrosion in a Buffered Media,” Corrosion Science 86 (2014) 93-100.
Sina S. Jamali, Simon E. Moulton, Dennis E. Tallman, Maria Forsyth, Jan Weber and Gordon G. Wallace, “Evaluating the Corrosion Behaviour of Magnesium Alloy in Simulated Biological Fluid by Using SECM to Detect Hydrogen Evolution,” Electrochimica Acta 152 (2015) 294-301.
Sina S. Jamali, Simon E. Moulton, Dennis E. Tallman, Jan Weber and Gordon G. Wallace, “Electro-Oxidation and Reduction of H2 on Platinum Studied by Scanning Electrochemical Microscopy for the Purpose of Local Detection of H2 Evolution,” Surface and Interface Analysis 47(13) (2015) 1187-1191.
Sina S. Jamali, Simon E. Moulton, Dennis E. Tallman, Maria Forsyth, Jan Weber, Azadeh Mirabedini and Gordon G. Wallace, “Corrosion Protection Afforded by Praseodymium Conversion Film on Mg Alloy AZNd in Simulated Biological Fluid Studied by Scanning Electrochemical Microscopy,” Journal of Electroanalytical Chemistry 739 (2015) 211-217.