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 - Kauss, N. A1 - Heyn, A. A1 - Rosemann, Paul T1 - How to Detect Sensitivity on Aged Lean-Duplex Stainless Steel With Electrochemical Methods N2 - The influence of isothermal ageing on microstructure, sensitisation and pitting corrosion resistance of the lean duplex stainless steel (LDSS) X2CrNiN23-4 was investigated with various electrochemical methods. The aging at 600 °C (from 0.1 h up to 20 h) lead to the formation of precipitations at the ferrite-ferrite (α/α) and ferrite-austenite (α/γ) grain boundaries, inducing sensitisation due to chromium depletion. The degree of sensitisation was evaluated with the double loop electrochemical potentiokinetic reactivation method (DL-EPR) according to ASTM G108 and correlated with critical pitting potentials (Epit) as well as critical pitting temperature (CPT) measured in an electrolyte according to ASTM G48 using electrochemical noise. Up to an ageing time of 1 h, the sensitisation did rise significantly, stabilising at a nearly constant level with a slight drop at 20 h. This behaviour correlated perfectly with the potentiodynamically determined pitting potentials Epit and sensitisation. The CPT showed a higher sensitivity at short ageing times compared to the DL-EPR and Epit. Finally, the KorroPad method was applied to visualise the sensitisation induced reduction of pitting corrosion resistance. The “KorroPad” is an agar-based gel-electrolyte containing 0.1 mol/l sodium chloride (NaCl) and 0.1 mol/l potassium ferricyanide III (K3[Fe(CN)6]), invented at the Federal Institute of Materials Research and Testing in Berlin (Germany) to detect surfaces of stainless steel prone to pitting corrosion. The standard configuration of the KorroPad showed no differentiation for the various aging conditions. Increasing the concentration of both NaCl and potassium ferrocyanide III to 0.5 M shifts the detection limit of the KorroPad method to stainless steels with higher corrosion resistance, producing the same trends detected by standard electrochemical pitting corrosion values (Epit, CPT) and sensitisation (DL-EPR). By that, the KorroPad method was successfully adjusted to the lean-duplex stainless steel X2CrNiN23-4, enabling short-time testing to detect sensitization. T2 - Electrochemical Methods in Corrosion Research 2018 CY - Cambridge, UK DA - 22.07.2018 KW - Corrosion testing KW - Duplex stainless steels KW - Corrosion KW - KorroPad KW - Pitting corrosion KW - EPR KW - Electrochemical noise KW - Stainless steel PY - 2018 AN - OPUS4-45615 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Heyn, A. A1 - Rosemann, Paul A1 - Babutzka, Martin A1 - Bender, S. T1 - Electrochemical noise of unalloyed steel in mixtures of water-based binders and pigments N2 - The development of organic coatings for corrosion protection is an elaborate process with a multitude of often interminable investigations and tests of protection properties. Electrochemical methods support the processes of development to a great extent and help to understand mechanisms of action and failure. They are usually carried out on applied coating systems with a completed formulation. An examination possibility is presented in this publication that enables the characterization of waterbased coatings with different formulation variations in the liquid (aqueous) state with the aid of electrochemical noise technique. Thus, selection of binders, pigments, and other additives is supported essentially and made more efficient in a very early Phase of formulation development. The paper shows that a unique insight into the dynamic processes of a metal in contact with an aqueous coating dispersion is possible using the example of the development of zinc-free corrosion-inhibiting pigments for waterbased coatings. In addition, it is presented in which way the results correlate with the performance of applied coatings. KW - Organic coatings KW - Electrochemical noise KW - Corrosion KW - Corrosion protection KW - Corrosion protection pigments PY - 2017 U6 - https://doi.org/10.1002/maco.201709671 SN - 0947-5117 SN - 1521-4176 VL - 68 IS - 12 SP - 1295 EP - 1301 PB - Wiley-VCH Verlag CY - Weinheim AN - OPUS4-43319 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER -