Browsing by Author "Dickinson, Wayne H."

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Electrochemical concepts and techniques in the study of stainless steel ennoblement
(1998) Dickinson, Wayne H.; Lewandowski, Zbigniew
Electrochemical interactions of biofilms with metal surfaces
(1997) Lewandowski, Zbigniew; Dickinson, Wayne H.; Lee, Whonchee
Two mechanisms of microbially influenced corrosion (MIC) are discussed and compared: corrosion modified by the presence of (1) sulfate-reducing bacteria (SRB) and (2) manganese-oxidizing bacteria (MOB). It is demonstrated that the nature of MIC in both cases depends on the nature of inorganic materials precipitated at the metal surface, iron sulfides and manganese oxides. Those materials are electrochemically active and, therefore, modify the electrochemical processes naturally occurring at the metal-solution interface. Some of these modifications may lead to accelerated corrosion.
The ennoblement of stainless steel by manganic oxide biofouling
(1996-08) Dickinson, Wayne H.; Caccavo, Frank; Lewandowski, Zbigniew
Twenty-three 316L stainless steel (SS) coupons were exposed in situ to fresh river-water for periods of up to 35 days. All samples developed steady-state corrosion potentials (Ecorr) near + 350 mV (SCE) and polarization measurements showed enhanced cathodic current density characteristic of passive metal ennoblement. Epifluorescence and scanning electron microscopy of the attached biofilm showed numerous 10–20μm diameter Mn-rich annular deposits, associated clusters of bacterial cells, and abundant sheathed bacteria. Dissolution of the Mn deposits using Na2SO3 shifted Ecorr to pre-exposure values. SS coated with MnO2paste displayed electrochemical behavior nearly identical to that of ennobled samples. A mechanism of ennoblement by MnO2 biofouling is proposed which explains a variety of findings on the electrochemical behavior of microbially colonized SS.
Evidence for surface changes during ennoblement of type 316l stainless steel: dissolved oxidant and capacitance measurements
(1996-12) Dickinson, Wayne H.; Lewandowski, Zbigniew; Geers, R. D.
Ennobled open-circuit potential (Ecorr) for type 316L stainless steel (SS [UNS S31603]) exposed to fresh river water was investigated using microelectrodes to measure dissolved oxygen (DO), hydrogen peroxide (H2O2), and local Ecorr within biofouling deposits. Galvanostatic techniques were used to measure capacitance (C) and to titrate reducible surface material. Results indicated deposits were uniformly aerobic and did not contain elevated levels of cathodic depolarizers. Development of ennobled potential was related to Ecorr near the beginning of exposure and occurred on surfaces with as little as 3% to 5% biofouling coverage. Galvanostatic measurements revealed a strong correlation between C and Ecorr as Ecorr increased during biofouling. Galvanostatic reduction measurements indicated increased abundance of reducible surface-bound material during the same period. Results suggested an ennoblement mechanism involving modifications of the metal oxide surface.
Manganese biofouling and the corrosion behavior of stainless steel
(1996-09) Dickinson, Wayne H.; Lewandowski, Zbigniew
Manganese‐ and iron‐oxidizing bacteria (MFOB) are widely implicated in microbially influenced corrosion, often in association with sulfate‐reducing bacteria (SRB). Traditionally MFOB have been assigned a passive role in the corrosion process, promoting differential aeration cells, and providing oxygen depleted conditions conducive to the growth and corrosive attack of SRB. Recent work, summarized in this article, demonstrates that manganese biofouling alters the electrochemical behavior of stainless steel (SS), and suggests that MFOB are more active in localized corrosion than traditionally held. The paper discusses the chemistry and potentially corrosive impact of manganese and iron oxides on SS, explores the possible relationship between MFOB and SRB, and proposes a model to describe the synergistic influence these organisms may exert in the corrosion process.
Mic issues: commentary from the corrosion 2002 mic panel discussion
(2002) Lewandowski, Zbigniew; Cloete, Thomas E.; Dexter, Stephen C.; Dickinson, Wayne H.; Kikuchi, Yasushi; Little, Brenda J.; Rossmoore, Harold; Sand, Wolfgang; Videla, Hector A.
Invited panelists, prominent Microbiologically Influenced Corrosion (MIC) researchers from universities, government agencies, and industrial companies, were asked to select and to present issues they felt were vital to understanding MIC. The discussion took place during the MIC symposium at the NACE 2002 Conference in Denver. The notes presented in this paper are commentary from this discussion.