This sequence is optimised for a VoltaLab 21 - If you use another VoltaLab system, you must edit the sequence.

You must open and close EVERY method so that your instrument declared in [Setting\instrument] is taken in account. Then you can save the sequence under a new name and run it with your own VoltaLab system. Method General corrosion (Rp) **************************************** Files General corrosion (Rp) .EXP General corrosion (Rp) 002_15.CRV General corrosion (Rp) 22.crv **** ABSTRACT The Rp polarisation resistance is an important parameter to evaluate the anti-corroding strength of a corrosion inhibitor or to study a uniform corrosion process at a metal surface. The polarisation resistance variations versus time are automatically recorded. Each experimental point (polarisation resistance and potential versus time) is obtained from one individual voltammetry which is automatically processed with a special algorithm [1]. These individual voltammetries are saved. That makes it possible to process them by means of the 2nd Stern method for instance. Between two successive voltammetries, the system is left at rest (the circuit is open) during a waiting time set by the user. **** SAMPLE Solution CaCl2 0.01M in tap water WORK Copper disc ( diameter=2mm) REF Calomel AUX Platinum Cell CP06 (not thermostated) **** SETTINGS - EXPERIMENTAL Solution CaCl2 0.01 M in tap water at room temperature. Areas for WORK equals 1 cm. Current densities are assimilated to currents in these conditions. The potential is scanned 25 mV (Overvoltage) from the OCP of the system at a Scan rate of 5 mV/s (start at OCP, potential scanning toward OCP - 25 mV and potential scanning toward OCP + 25 mV). The circuit is open during 5 minutes between two successive individual voltammetries. This waiting time enables the WORK to stabilise its zero-current potential. At the end of the experiment, the system is left at the free potential (Open circuit at end = Yes). The 10 individual voltammetries are saved as well as the polarisation potential and corrosion potential (open circuit potential) versus time. **** CURVE EXAMINATION 1) With the file General corrosion (Rp) 22.crv Display: Type = Normal X = Time Y1 = Resistance

Y2 = Potential

This file comprises 9 experimental points. Each point corresponds to an automatic calculation of the polarisation resistance according to a specific algorithm dedicated to inhibitors studies [1] The values for point number 2 (which correspond to the third point) are given with the cursor.

Polarisation resistance = Rp = 150 kohm.cm Open circuit potential = Potential = -50.7 mV These results can be compared with the results obtained with Rp determination in post run processing obtained from a linear regression or Stern equation. 2) With the file General corrosion (Rp) 002_15.CRV Traject: Path=Forward Cycle=1 Display: Type = Normal X = Potential Y1 = Current

Y2 = No

This file is the third file out of the 9 individual cyclic voltammetries recorded. Each voltammetry i = f(E) can be processed manually with the linear regression or the Second Stern calculations to evaluate the corrosion potential and the polarisation resistance. It must be underlined that the experimental conditions are not valid to perform Tafel calculation since the overvoltage applied versus the open circuit potential is smaller (25 mV) than the overvoltage required for Tafel calculation (200 mV). Calculations are performed on the traject which correspond to the anodic scan. Use the Traject post processing tool to select this part of the curve prior to the calculations. 2) a) Calculate the polarisation resistance according to a linear regression Traject: Path=Forward Cycle=1 Display: Type=Normal X=Current Y1=Potential Y2=No Linear regression----------------------- 17-09-1999, 13:32:23 X min. : -104.999 X max. : 200.001 Mode : y=f(x) Result : y(mV) = 0.179*x(nA/cm) -58.898 x(y=0) = 330.086 Coefficient : 0.990803 Polarisation resistance = Slope = 179 kohm.cm Zero current potential = -58.8 mV 2) b) Calculate the polarisation resistance according to the 2nd Stern equation Traject: Path=Forward Cycle=1 Display: Type=Normal X=Potential Y1=Current Y2=No Calculate the polarisation resistance according to the 2nd Stern equation 17-09-1999, 13:37:24 Smoothing : 9 Segment : 25 mV E(i=0) : -60.4 mV Rp : 206.90 kohm.cm Coefficient : 0.993 Polarisation resistance = Rp = 206.9 kohm.cm Zero current potential = E(i=0) = -60.4 mV **** CONCLUSION

The difference between the polarisation resistance determined automatically and values determined by linear regression or Stern analysis is due to the differences of the algorithms used for the calculations. The difference between the "Zero current potential = E(i=0) and the "open circuit potential" is due to the fact that it is not the same potential. The Open Circuit Potential corresponds to the potential of the WORK at rest, prior to the individual voltammetry. The zero current potential E(i=0) corresponds to the potential at which the measured current is close to zero during the voltammetry when the potential is scanned in anodic direction. **** REFERENCES & NOTES [1] Calculations are performed according to the GFC-L-109-A-90 Standard - Consult the Help in General corrosion (Rp): How are determined Rp values?
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This sequence is optimised for a VoltaLab 80 - If you use another VoltaLab system, you must edit the sequence. You must open and close EVERY method so that your instrument declared in [Setting\instrument] is taken in account. Then you can save the sequence under a new name and run it with your own VoltaLab system. Method CV interactive ***************************** Files Vertex CV interactive .EXP Vertex CV interactive 01I.CRV **** ABSTRACT Platinum (Pt) is known as an "inert" metal with a strong catalytic activity for many electrochemical reactions. Many components can be adsorbed on Pt surfaces and the adsorption of hydrogen is a well known phenomenon in electrochemistry. This experiment concerns two fundamental mechanisms which occur on a Pt electrode polarised in a strong acid media, H2SO4 [1]. * Cathodic area: Hydrogen adsorption / desorption (from - 250 mV to + 200 mV versus Calomel) * Anodic area: Platinum "oxides" formation and reduction (from + 200 mV to 1300 mV versus Calomel) This extract from a CV interactive establishes the correlation between the anodic excursion which generates Pt oxides (from 0.6 V) and their cathodic reduction [1]. **** SAMPLE Solution H2SO4 0.5 M WORK Platinised platinum Plate 5X5 mm (CDC641T conductivity cell) REF Calomel electrode (XR100) AUX Platinum wire (XM100) CP06 cell at room temperature (22C) without nitrogen bubbling **** SETTINGS - EXPERIMENTAL Scan rate 50 mV/s (5 mV potential steps). A Chrono amperometry starts the sequence. It polarises the WORK at -300 mV /REF to stabilise the WORK interface and to saturate the solution with H2 in the vicinity of the WORK.

**** CURVE EXAMINATION 1) Display: Type = Normal X = Potential Y1 = Current Y2 = No The peak magnitude and the peak position depends upon the anodic potential vertex 2) Display: Type = Normal X = Time Y1 = Current Y2 = Potential The anodic potential vertex has been adjusted during the experiment. 3) Display: Type = Normal X = Time Y1 = Current Y2 = Quantity (C) To evaluate the reversibility of the anodic reaction it is also possible to display Q (charge) versus potential since Q is recorded along with current during the experiment. As an alternative, a Peak analysis will evaluate if the charge of the anodic peak equals the charge of the cathodic peak, for instance within the 3rd cycle. ****Reversibility with Peak analysis Determine the peak and integrate the peak with user selected base line 03-02-1999, 16:20:35 DATA Base line Mode : No Point 1 : 190.109 sec. Point 2 : 226.06 sec. Equation : y=0 RESULTS Integration Point 1 : 190.109 sec. Point 2 : 226.06 sec. Total : 5.003 mC/cm Positive : 63.77 mC/cm Negative : -58.7 mC/cm Peak Position : 219.958 sec. Height : -11.559 mA/cm Width : 14.346 sec. The excess in positive charge calculated with peak analysis with a manual base line can be interpreted as oxygen gas evolution. This value is in good accordance with the values "Quantity (C)". **** CONCLUSION The interactive cyclic voltammetry establishes the correlation between the anodic excursion which generates Pt oxides (from 0.6 V) and their cathodic reduction [1]. The more anodic the potential limit, the bigger the peak: the peak magnitude and the peak position are correlated with the anodic potential vertex. **** REFERENCES [1] P.A. Christensen and A. Hamnett in "Techniques and Mechanisms in Electrochemistry", p228 Blackie A&P (Imprint of Chapman&Hall, Glasgow, 1994)
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This sequence is optimised for a VoltaLab 21 - If you use another VoltaLab system, you must edit the sequence. You must open and close EVERY method so that your instrument declared in [Setting\instrument] is taken in account. Then you can save the sequence under a new name and run it with your own VoltaLab system.

Method Pitting corrosion ****************************** Files Pitting.EXP Pitting-0.4C008.CRV Pitting 50C008.CRV **** ABSTRACT The "pitting potential" and the "repassivation potential" of 316L stainless steel are experimentally determined at -0.4 C and 50C in NaCl 3g/l. They are determined from the experimental polarisation curve. **** SAMPLE Solution: NaCl 3g/l in water WORK Stainless steel disc EM/EDI/INOX AISI 316L (C<0.03%,Cr=17%,Ni=12%,Mo>2%) on a rotating disc electrode at 500 rpm ( EDI101 with its CTV101 Speed control Unit) REF Calomel electrode(XR100) AUX Platinum wire (XM100) A/D IN Temperature in C (T201) Digital Thermometer with analogue output CP06 Thermostated cell, temperature maintained with bath flow circulation. **** SETTINGS - EXPERIMENTAL The polarisation curve is recorded at 5 mV/s from OCP toward anodic potentials up to 1.5 mA and after 10 seconds at this potential, the potential scan is reversed in cathodic direction. **** CURVE EXAMINATION 1) Display: Type = Normal X = Potential Y1 = Current Y2 = A/D IN (Temperature in C) Overlay the two experimental pitting curves: Pitting-0.4C008.CRV (red) Pitting 50C008.CRV (blue) and use the "Axis" function to distinguish Y1 from Y2. The "pitting potential" corresponds to the potential at which the current starts to increase on the anodic scan. The "repassivation potential" corresponds to the potential at which the current becomes negligible on the reverse (cathodic) scan. The more anodic the "pitting potential", the less subject to pitting the sample. A "repassivation potential" close to the "pitting potential" indicates that the sample is capable of reprotecting itself easily after pitting. **** CONCLUSION The sample under examination is much less sensitive to pitting corrosion at -0.4C than at 50C.
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This sequence is optimised for a VoltaLab 80 - If you use another VoltaLab system, you must edit the sequence. You must open and close EVERY method so that your

instrument declared in [Setting\instrument] is taken in account. Then you can save the sequence under a new name and run it with your own VoltaLab system. Method Fe2+&Fe3+.EXP ***************************** Files Fe2+&Fe3+ 5 cycles 100 mVs-1__5.CR Fe2+&Fe3+ 5 cycles 250 mVs-1 100 rpm__5.CRV Fe2+&Fe3+ 5 cycles 250 mVs-1 200 rpm__5.CRV Fe2+&Fe3+ 5 cycles 500 mVs-1__5.CRV Fe2+&Fe3+ 500 mVs-1 1000 rpm variable conc _5.CRV **** ABSTRACT This sequence will help you to become familiar with your VoltaLab system and with some of the fundamental principles of electrochemistry, the relationship between scan rate, concentration convection (rotation speed) and the current. Prior to run it, we recommend you to play the "Virtual Fe2+&Fe3+.EXP" file in virtual mode. You will also benefit from the Radiometer analytical poster entilted "UNDERSTANDING ELECTROCHEMISTRY". From one trial to another you are invited to modify the scan rate, the concentration and the EDI rotation speed. You can evaluate the impact of these modifications on the voltammogram. The scan rate: The higher the scan rate the higher the peak and the current limit The concentration in "BS870": The higher the concentration the higher the peak and the current limit The EDI rotation speed: The higher the EDI rotation speed the higher the current limit **** SAMPLE BS870 is the commercial name of a standard solution available from Radiometer Analytical E {Fe2+/Fe3+} at 25 C 215 mV 4 mV versus ECS 261 mV 4 mV versus Ag/AgCl Solution BS870 diluted in deminalerised water (2 ml of BS870 in 50 ml of water) WORK Platinum rotating disc electrode (EM-EDI-Pt) REF Calomel electrode (XR110) AUX Platinum wire (XM100) The RDS010 Rotating Disc Stand is recommended. The RDS010 Rotating Disc Electrode Stand is very convenient for this type of practical workshop since the rotating speed is directly controlled from VoltaMaster 4. **** SETTINGS - EXPERIMENTAL The default values in Fe2+&Fe3+.EXP for the cyclic voltammetry must be modifyed in order to illustrate the various possibilities. **** CURVE EXAMINATION Run the Virtual Fe2+&Fe3+.EXP to obtain the comments.

**** CONCLUSION With BS870 it is very simple to verify some of the fundamental equations presented in the "UNDERSTANDING ELECTROCHEMISTRY" poster. Thes equations are also available from VoltaMaster 4 Help: type "Equations" in the index. The higher the scan rate the higher the peak and the current limit The higher the concentration the higher the peak and the current limit The higher the EDI rotation speed the higher the current limit
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This sequence is optimised for a VoltaLab 80 - If you use another VoltaLab system, you must edit the sequence. You must open and close EVERY method so that your instrument declared in [Setting\instrument] is taken in account. Then you can save the sequence under a new name and run it with your own VoltaLab system. This sequence aplies +400mV (versus the reference electrode) in order to detect Cu(I) at the ring electrode/potentiostat. VoltaLab Bipotentiostat = 2 PGZ ************************************** Files EAD_Copper.EXP EAD_Copper005.CRV EAD_Copper011.CRV **** ABSTRACT A 10 mV/s linear voltammetry is operated on the disc electrode from +400mV down to 600mV (versus the reference electrode) while the potential on the ring electrode is set at +400mV (versus the same reference electrode) in order to detect Cu(I). **** SAMPLE Working Electrode : Rotating Ring and Disc electrode Pt/Pt type EAD Rotation speed = 2500rpm Reference Electrode : XR110 Auxiliary Electrode : XM110 Solution CuCl2 0.01M KCl 0.5M Cooper ? solution Working electrode 1 = Platinum Disc (production) Working electrode 2 = Platinum Ring (detection) Auxiliary electrode = Platinum wire Reference electrode = Calomel **** SETTINGS - EXPERIMENTAL Two PGZ are operated simultaneously and the potentiostat which drives the ring records the ring current and the disc current, thaks to the A/D IN additionnal input channel. *PGZ One WORK Cell Disc WORK Ring

AUX Short circuited with the PGZ One REF REF Short circuited with the PGZ One AUX * PGZ One settings (Disc) Pot. Linear V--------------------------- 18-11-1999, 11:24:47 Potential 1: 400 mV/REF Potential 2: -600 mV/REF Duration: 0.025 sec. Step: 0.25 mV Scan rate: 10 mV/sec. Sampling rate: 1:16 Priority auto ranging: Yes Maximum range: Auto Minimum range: 1 A D/A OUT initial: 1250 mV D/A OUT final: 0 mV A/D IN: Yes Open circuit at end: No Save points: Yes **PGZ Two WORK Cell ring AUX Cell AUX REF Cell REF ** PGZ Two settings (Ring) Chrono Amperometry---------------------- 29-11-1999, 11:39:24 Potential 1: 400 mV Duration 1: 10 min. Potential 2: 400 mV Duration 2: 10 min. Number of cycles: 1 Measurement period: 1 sec. Minimun current: -1 mA Maximum current: 1 mA Maximum range: 1 mA Minimum range: 1 mA Ohmic Drop Compensation: No Filter: Auto D/A OUT initial: 0 mV D/A OUT final: 0 mV A/D IN: No Open circuit at end: Yes **** CURVE EXAMINATION 1) Linear Voltammetry (EAD_Copper005.CRV) Display: Type=Normal X=Time Y1=Current Y2=Iring Y1 represents the disc current and Y2 represents the ring current.

1-a) Disc and ring According to [1], two waves are detected on the disc which correspond to the reaction (1) and then (3) while the ring exhibit a signal which increases during the first disc wave and then decreases. This reaction correspond to the reaction (3). When the disc reaches a potential which corresponds to the second wave, the reaction which is taking place on the disc is cooper deposition; there is no more Cu(+) which can be captured by the ring. As a consequence, the ring current falls to zero. (1) [Cu(2+)] <==> [Cu(+)] e = +0.16 V / HSE (2) [Cu(2+)] <==> [Cu(0)] e = +0.34 V/SHE (3) [Cu(+)] <==> [Cu(0)] e= +0.52 V/SHE (4) [Cu(0)] + [Cu(2+)] --> [Cu(+)] 2) Open circuit potential (EAD_Copper011.CRV) Display: Type=Normal X=Time Y1=Potential Y2=Current Once the voltammetry is finished, the disc electrode regulation is opened but the regulation on the ring electrode continues. The Ring potential which is measured correspond to the open circuit potential of the ring. At the beginning, the ring is covered with copper [which results from the Cu(2+) deposition operated during the voltammetry]. One can say that the disc is a cooper disc. Since a spontaneous chemical oxidation of this cooper layer takes place (4), it takes less than one minute to disolve the cooper and obtain a platinum disc again. The variation of the potential correspond to that phenomenon. Since that chemical oxidation generates [Cu(+)], this [Cu(+)] can be detected on the ring. The current recorded in the meanwhile on the ring is Iring. During the chemical dissolution of the cooper, a significant current is recorded which correspond to the fact that Cu(+) are available and can be oxidised onto the ring. Once the cooper layer is completely dissolved, there are no more Cu(+) ions in solution and thus the ring current goes back to zero. Note: A +244 mV offset has been automatically applied to the experimental files in order to obtain their potential quoted versus SHE. The half potential calomel electrode used as reference is +244 mV/SHE [2] **** CONCLUSION It is convenient and simple to achieve bipotentiostatic experiment with VoltaLab. **** REFERENCES [1] Simultaneous and independant Potentiostatic control of two indicator electrodes D.T. Napp, DC Jonhson, and Stanley Bruckenstein. Analytical chemistry Vol 39, No4 april 1967. [2] Standard potentials in aqueous solution, ed. A.J. Bard, R. Parsons, and J. Jordan, Dekker, New York, 1985.
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This sequence is optimised for a VoltaLab 80 - If you use another VoltaLab system, you must edit the sequence. You must open and close EVERY method so that your

instrument declared in [Setting\instrument] is taken in account. Then you can save the sequence under a new name and run it with your own VoltaLab system. Method Cyclic Voltammetry *************************************** Files Ohmic Drop Compensation.EXP No ODC 035.CRV Dynamic ODC 045.CRV No ODC (Bis) 055.CRV Static ODC 075.CRV **** ABSTRACT Different modes of ohmic drop compensation are compared: No, Dynamic and Static auto using cyclic voltammetries performed with Pt in H2S04 [1] [3]. The cell resistance is determined (2.5 Ohms) and the cyclic voltammetries obtained with Dynamic and Static auto ODC exhibit a peak shift versus the cyclic voltammetry obtained with No ODC as expected from theory. (Peak shift = 25 mV = 10 mA * 2.5 Ohm). The cell resistance is measured and the potential Set value = Potential + Ohmic drop is recorded with the A/D IN additional channel. **** SAMPLE Solution H2SO4 0.5 M WORK Platinised platinum Plate 5X5 mm (CDC641T conductivity cell) [2] REF Calomel electrode (XR100) AUX Platinum wire (XM100) A/D IN E OUT (Potential output) **** SETTINGS - EXPERIMENTAL CP06 cell, temperature: ambient ( 22 C), without nitrogen bubbling. The initial Chrono coulometry performed at -300 mV /REF stabilises the WORK and saturates the solution with H2 in the vicinity of the WORK. The cyclic voltammetries were stabilised since the second cycle within every run. The experimental curves are "extract" of one cycle for each ODC mode. Scan rate 50 mV/s (5 mV potential steps). **** CURVE EXAMINATION Display: Type = Normal X = Potential Y1 = Current Y2 = No Overlay No ODC 035.CRV with Dynamic ODC 045.CRV, No ODC (Bis) 055.CRV and Static ODC 075.CRV and use the graphic data to distinguish between the curves with (blue) and without (red) ohmic drop compensation. For instance, select these representations: No ODC 035.CRV (red triangles) No ODC (Bis) 055.CRV (red line) Dynamic ODC 045.CRV (blue squares) Static ODC 075.CRV (blue line) **** CONCLUSION The different modes of ohmic drop compensation can be run within the same experiment and compared. The cell resistance determined either by Dynamic or Static auto is of the same value and is compensated so that the cyclic voltammetries obtained with Dynamic and/or Static auto ODC exhibit a peak shift versus the cyclic voltammetry obtained with

No ODC, as expected from theory. (Peak shift at 8 mA = 20 mV = 8 mA * 2.5 Ohm). The cell resistance is measured point per point with the Dynamic ODC and the Set value = Potential + Ohmic drop recorded with the A/D IN additional channel can be compared to the potential value. These two values are equal whenever there is No ODC or no current. The Dynamic ODC does not modify the look of the cyclic voltammetry obtained with Static auto and this proves that the determination of the cell resistance by impedance which is performed point per point in Dynamic mode does not modify the interface studied. **** REFERENCES & NOTES [1] P.A. Christensen and A. Hamnett "Techniques and Mechanisms in Electrochemistry" p228 - Blackie A&P (Imprint of Chapman&Hall, Glasgow, 1994 [2] Platinised platinum amplifies the catalytic effect of Pt. [3] Ronald Woods "Chemisorption at Electrodes" In "Electroanalytical Chemistry" Vol 9 pp 1-162 - M Dekker, 1976