Electrochemical systems for corrosion measurements Corrosion impact 02 Corrosion is the term general y used to describe oxida-For this reason, clear financial and technological benefits tive processes that result from the interaction of a metal result from monitoring these processes and developing with environmental elements like oxygen or water. The effective strategies against them. World Corrosion Organization estimates that corrosion has a yearly cost of more than the 3% of GDP world-wide. In the United States, e.g., this translates into 2.2 1) http://corrosion.org/wco_media/nowisthetime.pdf trillion dollars1). Reliable corrosion measurements via electrochemistry Electrochemical measurements of corrosion processes Over the past three decades, several methods have been Depending on the nature of the application, different introduced to measure corrosion. Many of these tradi-elec trochemical techniques can be applied in order to tional methods, such as weight loss and spray test analy-determine the parameters of interest. Metrohm offers sis, can be quick and cost-effective. Unfortunately, the ful y customizable hardware and software solutions to results that they yield are only qualitative. By contrast, perform electrochemical experiments and calculate cor-electrochemical analysis techniques yield accurate and rosion parameters. The software package offers dedi-reproducible quantitative data. cated methods for corrosion analyses that are in compli-ance with ASTM standards and industry best practices. Electrochemical techniques Parameters of interest ASTM standards DC techniques • Polarization resistance (Rp) • Linear sweep voltammetry • Corrosion rate (mm/year) • ASTM G102 • Tafel slope analysis • Corrosion current • ASTM G59 • Potentiodynamic polarization • Corrosion potential AC techniques • Film resistance and conductivity • Electrochemical Impedance • Charge-transfer resistance • ASTM G59 Spectroscopy (EIS) • Solution resistance • ASTM G106 • Electrochemical Frequency • Polarization resistance Modulation (EFM) Chrono and Other Techniques • Redox kinetics • Electrochemical Noise (ECN) • Pit initiation • ASTM G150 • Critical Pitting Temperature (CPT) • Crevice progression • ASTM G148 • Hydrogen permeation • Hydrogen resistance • ASTM G100 • Cyclic polarization • Surface morphology • Forced convection measurements Corrosion parameters by Linear Polarization Resistance (LPR) measurements The use of a potentiodynamic linear sweep measurement rate. Every instrument of fe red by Metrohm Autolab is 03 to quantify the corrosion processes is described in the equipped with a protocol for conducting a typical LPR ASTM G59 standard. Typical y, this technique is used to measurement consistent with the ASTM G59 standard. measure and monitor corrosion on a day-to-day basis. In this method, a three-electrode setup is em ployed Application with the sample of interest acting as the working elec - Corrosion monitoring and measurements in industries trode. A potential sweep is applied and the resulting and corrosion labs. current is measured. The polarization resistance can be extracted from the resulting data and the Tafel ap - Recommended configuration pro ximation can be applied to cal culate the corrosion PGSTAT204 + 1L ASTM corrosion cel Unique software features for LPR measurements • Linear polarization protocol with built-in OCP evaluation • Change voltage or scan rate during a measurement • Procedure scheduler: For long measurements or multiple runs, experiments can be scheduled with added wait times • High-resolution vectorial graphics with export and printing options • Automatic calculation of kinetic rate constants • Direct determination of polarization resistance and corrosion rates Polarization resistance Linear polarization analysis Corrosion parameters by Electrochemical Impedance Spectroscopy (EIS) 04 The use of electrochemical impedance spectroscopy With the FRA32M module, Metrohm Autolab offers the (EIS) is il ustrated in the ASTM G106 standard. Rather possibility of performing EIS measurements with poten-than a typical DC-based current-vs-voltage study, an tiostatic or galvanostatic control, over a frequency range AC signal is applied to the sample, the response is mea-of 10 μHz to 1 MHz, extendable to 10 MHz with the sured, and the impedance is then calculated. The data ECI10M module. We provide dedicated setups for EIS are then analyzed via fit and simulation, to yield film re-measurements according to the ASTM G106 standard, sistance, reaction kinetics, polarization resistance, and on single and multiple cells. other parameters which govern the corrosion processes and reaction mechanisms. The EIS technique is advanta-Application geous for the development of corrosion inhibitors and Coatings, corrosion inhibitor testing, and redox kinetics anti-corrosive films. analysis at corrosion research and testing labs. Unique software features for EIS analysis • Real-time EIS analysis and plot generation for: - Equivalent circuit fitting and simulation - Real-time AC signals, in time domain and frequency domain - Lissajous plots • Six predefined EIS protocols • Multiple EIS measurements with a single click • Multi-sine technique for quick low-frequency measurements • Possibility to sample the potential, current, time, and frequency domains • Electrochemical frequency modulation (EFM) measurements Impedance Nyquist and Bode plots Corrosion parameters by Electrochemical Noise (ECN) analysis ECN measures the fluctuations of the raw current and Application 05 potential, coming from the system, using a low-noise Corrosion in Cl−-containing electrolytes, pit initiation reference electrode or a zero-resistance ammeter (ZRA). stu dies, and crevice propagation. The data is examined visual y for spikes, or a Fourier trans form is applied to obtain a power density spectrum. Recommended configuration This yields important parameters for multiple applica-PGSTAT302N + ECN module tions in corrosion research. Metrohm Autolab instruments can be equipped with the dedicated ECN module which increases the potential resolution to 760 nV. Unique software features for ECN analysis • Protocol for power density plots • Automated ECN spectrum analysis • Built-in calculation of statistical indicators: - Skewness and kurtosis for current - Noise resistance - Pitting index ECN spectrum Critical Pitting Temperature (CPT) analysis 06 The ASTM standard G150 describes the use of CPT for Application stainless steel samples. This technique is mainly used Pit propagation, pitting resistance, and critical pitting to obtain relevant information on pit propagation and temperature for lab testing of stainless steel samples. critical pitting temperature of the samples. At a constant anodic potential, a simultaneous temperature increase is Recommended configuration applied at a rate of 1 ºC/min and the resulting current is PGSTAT302N + pX1000 module measured. The temperature at which a rapid increase in current is observed is the so-cal ed critical pitting temperature of the sample. Unique software features for CPT analysis • Temperature control in NOVA through RS232 control • Auto calibration routine for pX1000 temperature sensor • Multiple signal sampling for pH, voltage, and temperature • Procedure sequence editor Metrohm Autolab’s customized CPT analysis setup provides fully automated tem pe ra ture control and real-time plotting for current and temperature signals. Hydrogen permeation test Hydrogen permeation is the process in which hydrogen Application 07 penetrates and accumulates into the bulk of high-tensile-Hydrogen permeation study on metal sheets. stress stainless steel al oys; this introduces a cracking hazard. The use of the hydrogen permeation test is de-Recommended configuration scribed in the ASTM G148 standard using a Devanathan-Two floating instruments PGSTAT302F Stachurski cel . Electrochemical y control ed hydrogen permeation is mea sured using two electrolytic cel s that are separat-ed by the sample under study. Hydrogen is generated electrochemical y at the cathode, whereas the hydrogen that has diffused through the specimen is oxidized at the anode. The oxidation current is directly proportional to the amount of hydrogen diffusing through the metal membrane. Potentiostats that meet your application needs Parameter Compact Series N Series Multichannel Special – High Volt Floating Ground Compliance volts 10 V, 20 V 12 V, 30 V 10 V, 20 V 100 V 30 V (max) System current 100 mA, 400 mA, 100 mA, 400 mA, 1 A, 2 A, 10 A, 20 A 250 mA, 10 A 2 A (max) 10 mA 10 mA LPR, EIS, CPT, LPR, EIS, CPT, ECN, LPR, EIS, CPT, Concrete corrosion Hydrogen permeation, Applications Multiplexing Multiplexing Multiplexing testing, EIS, LPR LPR, EIS Corrosion cells that fulfill industrial guidelines ASTM Grade 1 L Corrosion Cell Complete 0.4 L Corrosion Cell Flat Corrosion Cell • Exposed surface area: 1 cm2 • Exposed surface area: 0.785 cm2 • Exposed surface area: 16.9 cm2 • Sample diameter: 14–16 mm • Sample diameter: 14 mm • Sample holder: PVC • Sample holder: PP • Sample holder: POM • Seal: Viton O-ring • Seal: Rubber • Seal: Viton Expand your applications with additional modules • FRA32M – Corrosion inhibitors study, research, and development • ECN – Characterization of coating failures • pX1000 – Critical pitting temperature measurements • MUX.MULTI4 – Sequential measurements on up to 64 cel s Measurement and results Product warranty Integrating over three decades of user experience, the All Metrohm Autolab instruments are backed by our NOVA software is designed to meet the requirements of in dustry-leading 3-year warranty. industrial and research users by providing the necessary functionality along with user-friendly flexibility. NOVA is equipped to insert ful y automated post-data analysis commands in every predefined procedure setup. The drag-and-drop functionality al ows easy operation for both basic and advanced users. G, CH-9100 Herisau ohm A witzerland by Metr www.metrohm.com , printed in S www.metrohm.co SW 12 Subject to change Layout by Ecknauer+Schoch A 8.000.5210EN – 2016-