TY - CONF A1 - Babutzka, Martin A1 - Reinemann, Steffi A1 - Heyn, Andreas T1 - Nachweis von Verarbeitungsfehlern bei nichtrostenden Stählen durch elektochemische Korrosionsuntersuchungen N2 - In diesem Beitrag soll an drei anschaulichen Beispielen dargestellt werden, wie sich Verarbeitungsfehler bei nichtrostenden Stählen auf das Korrosionsverhalten auswirken und zu unerwarteten Schäden führen können. Mit Hilfe von geeigneten elektrochemischen Verfahren werden Proben von drei unterschiedlichen nichtrostenden Stählen charakterisiert. An einem martensitischen nichtrostenden Stahl wird der Einfluss der Wärmebehandlung gezeigt, da dieser besonders empfindlich auf eine falsche Parameterwahl reagiert. Mit zwei austenitischen Stahlgüten wird verdeutlicht, wie sich Gefügeinhomogenitäten, die im Verarbeitungsprozess und bei der Stahlerzeugung entstehen, auf die Passivierung und das Lochkorrosionsverhalten auswirken. Dabei wird der Oberflächenzustand bei allen Untersuchungen gleich gehalten, um eine Rückführung des Korrosionsverhaltens auf die Gefügeinhomogenitäten durch den Vergleich mit Referenzchargen zu ermöglichen. T2 - 15. Sommerkurs Werkstoffe und Fügen am Institut für Werkstoff- und Fügetechnik CY - Magdeburg, Germany DA - 12.09.2014 PY - 2014 SN - 978-3-940961-85-3 SP - 197 EP - 206 AN - OPUS4-31475 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - 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 U6 - 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 - CHAP A1 - Bender, S. A1 - Göllner, J. A1 - Heyn, Andreas A1 - Blawert, C. A1 - Srinivasan, P.B. ED - Pekguleryuz, M.O. ED - Kainer, K.U. ED - Kaya, A. T1 - Corrosion and surface finishing of magnesium and its alloys N2 - While the possibilities of improving corrosion resistance (especially galvanic corrosion) by alloying are limited, surface finishing of magnesium alloys is the alternative for improving corrosion resistance. Due to the low corrosion potential of Mg and the danger of galvanic corrosion in the case of a coating defect, the choice of coatings is limited. This chapter will summarize the corrosion behavior of magnesium alloys and the metallurgical possibilities to improve the corrosion resistance of the alloys and reviewing critically the most commonly used surface treatments and coatings for magnesium. KW - Corrosion KW - Corrosion testing KW - Negative difference effect (NDE) KW - Conversion coatings KW - Plasma electrolytic oxidation KW - Organic coatings KW - Galvanic coatings PY - 2013 SN - 978-0-85709-088-1 SN - 978-0-85709-729-3 U6 - https://doi.org/10.1533/9780857097293.232 IS - Chapter 7 SP - 232 EP - 265 PB - Woodhead Publishing Ltd AN - OPUS4-29332 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - GEN A1 - Bender, S. A1 - Göllner, J. A1 - Heyn, Andreas A1 - Heilmaier, M. A1 - Schmidt, J. ED - Kainer, K.U. T1 - Basic examinations of pre-treatment and coating of magnesium alloys T2 - 8th International conference on magnesium alloys and their applications CY - Weimar, Germany DA - 2009-10-26 KW - Magnesium KW - Korrosion KW - Beschichtung KW - Vorbehandlung KW - Elektrochemisches Rauschen PY - 2010 SN - 978-3-527-32732-4 SP - 1323 EP - 1330 PB - Wiley-VCH AN - OPUS4-20743 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Bender, S. A1 - Heyn, Andreas T1 - Evaluation and Screening of the pre-treatment states of Mg-alloys using Electrochemical Noise N2 - A successful application of magnesium alloys as light structural materials and for special applications, such as in the medical sector, depends significantly on their corrosion properties. Since the use of well-chosen surface coating systems can optimize these properties, many efforts are going in this direction. In general, any coating process must be seen in a close connection to the pre-treatment of the alloy surface, particularly for magnesium alloys. The pre-treatment is required to prepare the optimal surface for a coating system, in which adhesion and dissolution behaviour are the central properties. In the case of magnesium alloys this means a well-controlled removal of the casting or rolling skin, which would be prone to corrosion and poor adhesion. Additionally, in most cases the surface morphology should be smooth. An investigation of different pickling solutions and pickling parameters showed a wide range of effectiveness (i.e., the resulting mass loss and surface morphology). Another important and often underestimated fact is the comparatively strong tendency of magnesium to react with the atmosphere. For that reason, after a completed pickling and cleaning treatment the condition of the surrounding atmosphere and the time prior to coating of the surface should be taken into account because of the formation of different reaction layers. These layers have an effect on adhesion and the corrosion properties of the coating system as a whole. For a documentation of the influence of different atmospheres and the timedependence of the surface activity the measurement of the electrochemical noise is the preferred technique. This is because it shows instantaneously the actual activity, even in the absence of external excitation. The influence of different pre-treatments as well as exposure conditions and duration was investigated using electrochemical noise measurements as a screening method. As a result the pretreatment which is an important part of the coating process could be considerably improved. T2 - EUROCORR 2009 CY - Nice, France DA - 2009-09-06 KW - Magnesium KW - Pre-treatment KW - Pickling KW - Electrochemical noise PY - 2009 IS - Paper 8080 SP - 1 EP - 8 AN - OPUS4-20064 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Bender, S. A1 - Holzhausen, U. A1 - Heyn, Andreas T1 - Investigations of the aqueous corrosion of pretreated magnesium alloys by means of electrochemical noise measurements N2 - An important possibility to improve the corrosion behaviour of magnesium alloys is the application of protective coatings. The quality of such coatings depends mainly on the pretreatment and the exposure conditions after pretreatment. Since magnesium surfaces change much faster under atmospheric conditions than those of almost any other technical material, it is necessary to pay special attention to this particular feature. The activity of acid-pickled surfaces of the magnesium alloys AZ31 and AZ91 in dependence on the exposure time and the humidity conditions was investigated with electrochemical noise (EN) measurements. In addition to pickling, plasma chemical vapour deposition processes open new possibilities for an economical, as well as ecologically quite safe, pretreatment. The results of EN investigations after acid pickling as well as specific plasma oxidation treatments of the two magnesium alloys after exposure to air with different humidities are presented. KW - Corrosion KW - CVD KW - Electrochemical noise KW - Magnesium alloys KW - Pretreatment PY - 2013 U6 - https://doi.org/10.1002/maco.201206741 SN - 0947-5117 SN - 1521-4176 VL - 64 IS - 8 SP - 708 EP - 713 PB - Wiley-VCH Verl. CY - Weinheim AN - OPUS4-29073 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Bosch, R.-W. A1 - Cottis, R.A. A1 - Csecs, K. A1 - Dorsch, T. A1 - Dunbar, L. A1 - Heyn, Andreas A1 - Huet, F. A1 - Hyökyvirta, O. A1 - Kerner, Z. A1 - Kobzova, A. A1 - Macak, J. A1 - Novotny, R. A1 - Öijerholm, J. A1 - Piippo, J. A1 - Richner, R. A1 - Ritter, S. A1 - Sánchez-Amaya, J.M. A1 - Somogyi, A. A1 - Väisänen, S. A1 - Zhang, W. T1 - Reliability of electrochemical noise measurements: Results of round-robin testing on electrochemical noise N2 - Sixteen laboratories have performed electrochemical noise (EN) measurements based on two systems. The first uses a series of dummy cells consisting of a 'star' arrangement of resistors in order to validate the EN measurement equipment and determine its baseline noise performance, while the second system, based on a previous round-robin in the literature, examines the corrosion of aluminium in three environments. All participants used the same measurement protocol and the data reporting and analysis were performed with automatic procedures to avoid errors. The measurement instruments used in the various laboratories include commercial general-purpose potentiostats and custom-built EN systems. The measurements on dummy cells have demonstrated that few systems are capable of achieving instrument noise levels comparable to the thermal noise of the resistors, because of its low level. However, it is of greater concern that some of the instruments exhibited significant artefacts in the measured data, mostly because of the absence of anti-aliasing filters in the equipment or because the way it is used. The measurements on the aluminium samples involve a much higher source noise level during pitting corrosion, and most (though not all) instruments were able to make reliable measurements. However, during passivation, the low level of noise could be measured by very few systems. The round-robin testing has clearly shown that improvements are necessary in the choice of EN measurement equipment and settings and in the way to validate EN data measured. The results emphasise the need to validate measurement systems by using dummy cells and the need to check systematically that the noise of the electrochemical cell to be measured is significantly higher than the instrument noise measured with dummy cells of similar impedance. KW - Electrochemical noise KW - Round-robin KW - Corrosion PY - 2014 U6 - https://doi.org/10.1016/j.electacta.2013.12.093 SN - 0013-4686 SN - 1873-3859 VL - 120 SP - 379 EP - 389 PB - Elsevier Science CY - Kidlington AN - OPUS4-30284 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Burkert, Andreas A1 - Heyn, Andreas T1 - Elektrochemische Methoden T2 - GfKORR-Seminar "Corrosion Monitoring - Entdecke die Möglichkeiten" CY - Frankfurt am Main, Germany DA - 2006-02-21 PY - 2006 AN - OPUS4-12135 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - GEN A1 - Burkert, Andreas A1 - Heyn, Andreas A1 - Ebell, Gino A1 - Lehmann, Jens A1 - Müller, Thoralf A1 - Mietz, Jürgen A1 - Fischer, Joachim T1 - Innovative Methoden in der Korrosionsforschung an der BAM N2 - Im Zusammenhang mit Planungs- und Entwicklungsaufgaben, den Forderungen in Normen und Regelwerken, in betrieblichen Arbeitsanweisungen, den Vorgaben für Zulieferteile oder bei der Auseinandersetzung mit Schadensfällen stellen sich häufig Fragen zum Korrosionsschutz sowie zu entsprechenden Prüf- und Untersuchungsverfahren. Die daraus gewonnenen Ergebnisse sollen z. B. eine Eignung von Werkstoffen oder Schutzsystemen unter spezifischen Einsatzbedingungen, die Dauerhaftigkeit des Schutzes, den Nachweis einer gleichbleibenden Qualität, die Vergleichbarkeit bekannter mit neuen Korrosionsschutzkonzepten oder den Wirkungsnachweis für gezielte Systemeingriffe belegen. Schnell wird deutlich, dass sich aus dem Blickwinkel verschiedener Branchen ganz unterschiedliche Anforderungsprofile ergeben, die ihren Niederschlag dann in unterschiedlichen Strategien der Prüf- und Untersuchungsverfahren finden. PY - 2014 SN - 978-3-00-044008-3 SP - 2-1 EP - 2-26 AN - OPUS4-32753 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Burkert, Andreas A1 - Heyn, Andreas A1 - Ebell, Gino A1 - Lehmann, Jens A1 - Poltavtseva, Marina T1 - Innovative Methoden in der Korrosionsforschung an der BAM T2 - 15. Sommerkurs Werkstoffe und Fügen am Institut für Werkstoff- und Fügetechnik CY - Magdeburg, Germany DA - 2014-09-12 PY - 2014 SN - 978-3-940961-85-3 SP - 53 EP - 64 AN - OPUS4-31479 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER -