TY - JOUR A1 - Bender, S. A1 - Goellner, J. A1 - Heyn, Andreas A1 - Schmigalla, S. T1 - A new theory for the negative difference effect in magnesium corrosion N2 - An unusual feature known as the negative difference effect (NDE) can be observed in magnesium when recording corrosion current density–potential curves. More hydrogen is evolved at a more positive potential which does not occur in conventional metals. Several models have been proposed in the literature in order to explain the phenomenon of NDE. They succeed in explaining some effects, and fail to deal with others. A new model, which explains the NDE by two electron consuming processes, is presented in this paper. By potentiostatic investigations of magnesium in a chloride electrolyte, measurements of hydrogen evolution and chemical analysis of the electrolyte the new model was experimentally verified. KW - Magnesium KW - Negativer Differenzeffekt KW - Korrosion KW - Korrosionsmechanismus KW - Current density-potential-curve KW - Magnesium alloys KW - Magnesium corrosion KW - Negative difference effect KW - Polarization measurements PY - 2012 DO - https://doi.org/10.1002/maco.201106225 SN - 0947-5117 SN - 1521-4176 VL - 63 IS - 8 SP - 707 EP - 712 PB - Wiley-VCH Verl. CY - Weinheim AN - OPUS4-25162 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Sarmiento Klapper, Helmuth A1 - Goellner, J. A1 - Burkert, Andreas A1 - Heyn, Andreas T1 - Environmental factors affecting pitting corrosion of type 304 stainless steel investigated by electrochemical noise measurements under potentiostatic control N2 - Electrochemical noise measurements on anodically polarised type 304 stainless steel surfaces in contact with buffer solutions of neutral pH were performed to study the effect of chloride ions in the nucleation of pitting corrosion. Passive layer stability and susceptibility to pitting corrosion after pickling and passivation at different environmental conditions were also investigated by means of electrochemical current noise measurements under cathodic and anodic polarisation. According to the obtained experimental results pits nucleate independently on the presence of chloride ions. It has been also shown that protectiveness of stainless steel surfaces after pickling strongly depends on the relative humidity of the environment in which the surface is subsequently passivated. KW - A. Stainless steel KW - C. Pitting corrosion KW - C. Passivity KW - B. Potentiostatic PY - 2013 DO - https://doi.org/10.1016/j.corsci.2013.06.005 SN - 0010-938X VL - 75 SP - 239 EP - 247 PB - Elsevier Ltd. CY - Orlando, Fla. AN - OPUS4-29662 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Sarmiento Klapper, Helmuth A1 - Goellner, J. A1 - Heyn, Andreas T1 - The influence of the cathodic process on the interpretation of electrochemical noise signals arising from pitting corrosion of stainless steels N2 - The use of electrochemical noise (EN) measurements for the investigation and monitoring of corrosion has allowed many interesting advances in the corrosion science in recent years. A special advantage of EN measurements includes the possibility to detect and study the early stages of localized corrosion. Nevertheless, the understanding of the electrochemical information included in the EN signal is actually very limited. The role of the cathodic process on the EN signals remains uncertain and has not been sufficiently investigated to date. Thus, an accurate understanding of the influence of the cathodic process on the EN signal is still lacking. On the basis of different kinetics of the oxygen reduction it was established that the anodic amplitude of transients arising from pitting corrosion on stainless steel can be decreased by the corresponding electron consumption of the cathodic process. Therefore, the stronger the electron consumption, the weaker the anodic amplitude of the EN signal becomes. EN signals arising from pitting corrosion on stainless steel can be measured because the cathodic process is inhibited by the passive layer. This was confirmed by means of EN measurements under cathodic polarisation. Since the cathodic process plays a decisive role on the form of transients arising from pitting corrosion, its influence must be considered in the evaluation and interpretation of the EN signals. KW - A. stainless steel KW - B. electrochemical noise KW - C. Pitting corrosion KW - C. Oxygen reduction PY - 2010 DO - https://doi.org/10.1016/j.corsci.2009.12.021 SN - 0010-938X VL - 52 IS - 4 SP - 1362 EP - 1372 PB - Elsevier CY - Orlando, Fla. AN - OPUS4-20880 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Sarmiento Klapper, Helmuth A1 - Heyn, Andreas A1 - Goellner, J. T1 - La técnica de ruido electroquímico para la investigación de la corrosión localizada: del fenómeno a la aplicación N2 - En los últimos anos el registro y análisis del ruido electroquímico ha posibilitado importantes avances en la investigación de fenómenos de corrosión localizada tales como el picado y la corrosión en rendijas. Así mismo, esta técnica a abierto enormes posibilidades para el monitoreo in situ de tales procesos corrosivos en la industria. Sin ninguna duda, la posibilidad de registrar en tiempo real y con extrema sensibilidad los procesos de nucleación de la corrosión localizada, hace de la técnica de ruido electroquímico una invaluable herramienta para alcanzar una mejor comprensión de su origen y propagación. A continuación se discutirán las fuentes de ruido electroquímico relacionadas con la corrosión localizada así como los avances alcanzados para una confiable adquisición y análisis de la información electroquímica suministrada por las senales de ruido electroquímico y se ilustrarán con ejemplos prácticos las ventajas de la técnica de ruido electroquímico para la evaluación de la corrosión localizada. KW - Ruido electroquímico KW - Corrosión localizada KW - Acero inoxidable KW - Aluminio KW - Elektrochemisches Rauschen KW - Korrosion KW - Passivität KW - Lochkorrosion PY - 2010 IS - November SP - 28 EP - 30 CY - Houston, TX, USA AN - OPUS4-23398 LA - spa AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER -