Conducting polymers for corrosion protection: What makes the difference between failure and success?

The potential of conducting polymer coatings for corrosion protection is a topic of current controversy. In general, the efficacy of conducting polymers very much depends on how they are applied and on the conditions of the corrosion experiment, i.e. depending on the exact conditions a conducting polymer may have excellent protection capability or may lead to a disastrously enhanced corrosive attack. A number of possible protection mechanisms are proposed. The most interesting corrosion protection mechanism that is currently discussed for conducting polymer-based coatings is the intelligent release of inhibitor anions. However, in many cases this does not work in the presence of larger defects. Based on scanning Kelvin probe studies of artificial defect initiated reduction and delamination of polypyrrole films in nitrogen (reduction) or air (reduction and delamination) atmospheres it will be shown in this paper that this is due to a switching from mixed anion release and cation incorporation during reduction of the conducting polymer to an exclusive cation incorporation for reduction over extended length scales. Although only results for polypyrrole are discussed here, for fundamental reasons this is postulated to be of general validity for all conducting redox polymers such as polypyrrole, polyaniline, and polythiophene. Hence, all coatings based on pure conducting polymer layers or pigments with macroscopic percolation networks will fail in the presence of larger defects, even though they may show excellent corrosion protection for smaller ones.

[1]  J. Heinze,et al.  Electropolymerization of Pyrrole and Electrochemical Study of Polypyrrole. 5. Controlled Electrochemical Synthesis and Solid-State Transition of Well-Defined Polypyrrole Variants , 2002 .

[2]  Michael Rohwerder,et al.  On the development of polypyrrole coatings with self-healing properties for iron corrosion protection , 2005 .

[3]  M. Plaza,et al.  Influence of polymerization time on the properties of polypyrrole-poly[bis(phenoxyphosphazene)] composites electrogenerated at constant current density , 2006 .

[4]  D. Tallman,et al.  Conducting Polymers and Corrosion: Polyaniline on Steel , 1999 .

[5]  W. Plieth,et al.  Release mechanism of electrodeposited polypyrrole doped with corrosion inhibitor anions , 2006 .

[6]  P. Pickup,et al.  Ion transport in polypyrrole and a polypyrrole/polyanion composite , 1993 .

[7]  G. Inzelt,et al.  Electrochemical quartz crystal microbalance study of ion transport accompanying charging-discharging of poly(pyrrole) films , 1999 .

[8]  Patrick J. Kinlen,et al.  A Mechanistic Investigation of Polyaniline Corrosion Protection Using the Scanning Reference Electrode Technique , 1999 .

[9]  L. Miller,et al.  The incorporation of electrolyte cations into polypyrrole and poly-3-methylthiophene during electrochemical reduction , 1987 .

[10]  Martin Stratmann,et al.  The Delamination of Polymeric Coatings from Steel. Part 1: Calibration of the Kelvinprobe and basic delamination mechanism , 1998 .

[11]  A. Malinauskas,et al.  Electrochemical response of ascorbic acid at conducting and electrogenerated polymer modified electrodes for electroanalytical applications: a review. , 2004, Talanta.

[12]  J. Heinze,et al.  Role of the formation potential on the redox processes of polypyrrole studied by an electrochemical quartz microbalance , 1993 .

[13]  M. Pyo,et al.  Cation and anion dominated ion transport during electrochemical switching of polypyrrole controlled by polymer-ion interactions , 1993 .

[14]  I. A. Hümmelgen,et al.  An electrochemically synthesized sulfonated polyaniline layer for positive charge carrier injection improvement in conjugated polymer devices , 2004 .

[15]  Michael Rohwerder,et al.  High-resolution Kelvin probe microscopy in corrosion science: Scanning Kelvin probe force microscopy (SKPFM) versus classical scanning Kelvin probe (SKP) , 2007 .

[16]  W. Megill,et al.  TITAN: a conducting polymer based microfluidic pump , 2005 .

[17]  A. Bund,et al.  The role of ion and solvent transport during the redox process of conducting polymers , 2006 .

[18]  M. Stratmann,et al.  The delamination of polymeric coatings from steel. Part 2: First stage of delamination, effect of type and concentration of cations on delamination, chemical analysis of the interface , 1998 .

[19]  M. Rohwerder,et al.  Conducting Polymers for Corrosion Protection: A Critical View , 2005 .

[20]  G. Wallace,et al.  Electroactive conducting polymers for corrosion control , 2002 .

[21]  W. Plieth,et al.  Semiconducting properties of polypyrrole films in aqueous solution , 1999 .

[22]  Fabienne Poncin-Epaillard,et al.  Polyaniline as a new sensitive layer for gas sensors , 2003 .

[23]  G. Stevens,et al.  The influence of unusual counterions on the electrochemistry and physical properties of polypyrrole , 1990 .

[24]  M. Stratmann,et al.  The deformation response of ultra-thin polymer films on steel sheet in a tensile straining test: the role of slip bands emerging at the polymer/metal interface , 2004 .

[25]  W. Plieth,et al.  Improvement of protection performance of polypyrrole by dopant anions , 2005 .

[26]  M. Musiani,et al.  Anodic synthesis of polyaniline coatings onto fe sheets , 1981 .

[27]  William H. Smyrl,et al.  Quartz Crystal Microbalance Study: Ionic Motion Across Conducting Polymers , 1991 .

[28]  M. Stratmann,et al.  On the atmospheric corrosion of metals which are covered with thin electrolyte layers. II, Experimental results , 1990 .

[29]  Martin W. Kendig,et al.  ‘Smart’ corrosion inhibiting coatings , 2003 .

[30]  Patrick J. Kinlen,et al.  Corrosion protection using polyanujne coating formulations , 1997 .

[31]  D. Worsley,et al.  Polyaniline Inhibition of Corrosion-Driven Organic Coating Cathodic Delamination on Iron , 2005 .

[32]  G. Shi,et al.  Conducting polymer electrochemical actuator made of high-strength three-layered composite films of polythiophene and polypyrrole , 2004 .

[33]  Martin Stratmann,et al.  On the atmospheric corrosion of metals which are covered with thin electrolyte layers—I. Verification of the experimental technique , 1990 .

[34]  U. Johanson,et al.  Comparative study of the behavior of anions in polypyrrole films , 2005 .

[35]  Yongfang Li,et al.  On the large overpotential of the first reduction of polypyrrole perchlorate films in organic solutions , 1997 .

[36]  Geoffrey M. Spinks,et al.  Conducting Polmers as a Basis for Responsive Materials Systems , 1998 .

[37]  M. Stratmann,et al.  Surface Modification by Ordered Monolayers: New Ways of Protecting Materials Against Corrosion , 1999 .

[38]  G. Wallace,et al.  Electrochemically controlled transport of small charged organic molecules across conducting polymer membranes , 1995 .

[39]  Siegfried Karg,et al.  Increased brightness and lifetime of polymer light-emitting diodes with polyaniline anodes , 1996 .

[40]  K. Jüttner,et al.  Development of an anion/cation permeable free-standing membrane based on electrochemical switching of polypyrrole , 1996 .

[41]  G. Wallace,et al.  Electroactive conducting polymers for corrosion control , 2002 .

[42]  A. Cook,et al.  Dopant Effects in Polyaniline Inhibition of Corrosion-Driven Organic Coating Cathodic Delamination on Iron , 2006 .

[43]  M. Keddam,et al.  Ions and solvent transport across conducting polymers investigated by ac electrogravimetry. Application to polyaniline , 2000 .

[44]  H. Takenouti,et al.  Device to Study Electrochemistry of Iron at a Defect of Protective Coating of Electronic Conducting Polymer , 2003 .

[45]  M. Stratmann,et al.  The delamination of polymeric coatings from steel Part 3: Effect of the oxygen partial pressure on the delamination reaction and current distribution at the metal/polymer interface , 1998 .

[46]  J. Heinze,et al.  Charging process in polypyrrole films: effect of ion association , 1998 .

[47]  T. Schauer,et al.  Protection of iron against corrosion with polyaniline primers , 1998 .

[48]  Alan G. MacDiarmid,et al.  Nobel Lecture: “Synthetic metals”: A novel role for organic polymers , 2001 .

[49]  I. Cantero,et al.  Conducting polymers as positive electrodes in rechargeable lithium-ion batteries , 1999 .

[50]  K. Jüttner,et al.  EQCM study of the ion exchange behaviour of polypyrrole with different counterions in different electrolytes , 2005 .

[51]  A. W. Hassel,et al.  An agar-based silver|silver chloride reference electrode for use in micro-electrochemistry , 1999 .

[52]  A. MacDiarmid,et al.  Electrochemical Characteristics of “Polyaniline” Cathodes and Anodes in Aqueous Electrolytes , 1985 .

[53]  Geraint Williams,et al.  Factors Affecting Acid-Base Stability of the Interface Between Polyaniline Emeraldine Salt and Oxide Covered Metal , 2005 .

[54]  B. Wessling.  Corrosion prevention with an organic metal (polyaniline): Surface ennobling, passivation, corrosion test results , 1996 .

[55]  A. Öpik,et al.  Corrosion behavior of polypyrrole coated mild steel , 1999 .

[56]  A. Heeger.  Nobel Lecture: Semiconducting and metallic polymers: The fourth generation of polymeric materials* , 2001 .

[57]  V. Sammelselg,et al.  Electrochemical properties of cation sensitive polypyrrole films , 1998 .

[58]  M Vijayan,et al.  Biosensing and drug delivery by polypyrrole. , 2006, Analytica chimica acta.

[59]  David W. DeBerry,et al.  Modification of the Electrochemical and Corrosion Behavior of Stainless Steels with an Electroactive Coating , 1985 .

[60]  Ingemar Lundström,et al.  Polypyrrole micro actuators , 1999 .

[61]  Hideki Shirakawa,et al.  Nobel Lecture: The discovery of polyacetylene film-the dawning of an era of conducting polymers , 2001 .