Name: potentiodynamic corrosion testing
Uploaded: 2016-09-04T14:00:00.000+00:00
Duration: 8 min 43 s
Description: Watch this Scientific Journal Video about Potentiodynamic Corrosion Testing at JoVE.com

The authors had no funding provided for this study.

1. Construction of the Sample Holder
<ol>
	<li>Construct the sample holder from stainless steel spacers and a M3 stainless steel threaded screw, held in place with a M3 hexagonal nut.</li>
	<li>Remove the head of the threaded screw using pliers and polish the cut segment to maintain the thread pattern.</li>
	<li>When all individual components are ready, assemble the electrode holders. Each electrode holder contains three spacers joined together by the M3 screws resulting in an 11.5 cm handle. Place the hexagonal nuts at the junction of the screw and spacers to lock the connection.</li>
	<li>Solder (60/40% Sn/Pb) a toothless alligator clip onto the screw at the end of the rod. This will ensure a firm hold to later attach the electrode during analysis.</li>
	<li>Once the electrode holders are assembled, apply multiple coats of stop-off lacquer (electrical sealant) to prevent the stainless steel rods from corroding whilst immersed in the corrosion chamber.
	<ol>
		<li>Place all electrode holders with the samples attached to the alligator clip into a fume hood prior to coating. Place a 20 ml syringe into the fume hood. Use the syringe to collect the stop-off lacquer.</li>
		<li>Turn on the fume hood and pour the stop-off lacquer into a small glass jar. Pull 10 ml of stop-off lacquer into the syringe and coat the surface of the electrode holders. Make sure not to cover the test sample, which is going to be analyzed for corrosion.</li>
		<li>Coat half of each electrode holder and place in the fume hood to dry before coating the other half. This will help obtain a complete well-sealed coat without damaging the areas to be coated. Ensure that during the drying phase, the freshly coated regions do not touch other surfaces, as this will ruin the applied coat.</li>
		<li>Place the electrode holders in an elevated position during drying with no contact to any surfaces. Coat the electrodes quickly due to the quick solidification of the stop-off lacquer. This completes the first layer.</li>
		<li>Once dry, repeat the process to obtain 3 coats along the entire area.</li>
	</ol>
	</li>
	<li>Before commencing the corrosion run, leave the holders to dry for 24 hr after the completion of the final coat. All coating processes occur at RT, no heating or cooling steps are required although they may accelerate/decelerate the curing process.</li>
	<li>Making a faraday cage
	<ol>
		<li>Construct a Faraday cage by coating two plastic containers of the same size with 4 layers of aluminum foil to cover all sides.</li>
		<li>Cut two small holes out at the rim of upper plastic container to allow the electrode connection to the potentiostat and the nitrogen line to the nitrogen tank to pass through. A split design of the Faraday cage allows the upper component to be removed at the end of a run without needing to replace the lower section housing the tank.</li>
		<li>Fit the outer compartment (water chamber) into the Faraday cage. Leave the second half to the side and place on top of the lower compartment only when the corrosion vessel has been sealed (later in the procedure).</li>
	</ol>
	</li>
</ol>
2. Cleaning of Glassware
<ol>
	<li>Clean the corrosion vessel (700 ml cylindrical flask) before every corrosion run. Scrub the vessel with household detergent and rinse thoroughly with tap water. Repeat this step 3 times.</li>
	<li>Rinse the corrosion vessel 3 times with de-ionized water (DI) water to remove potential contaminants found in tap water.</li>
	<li>Once rinsing with DI water is completed pour 300 ml of 95% ethanol into the corrosion vessel and swirl around to contact all internal surfaces. Pour out the ethanol and repeat this step 3 times.</li>
	<li>Leave the corrosion vessel under a fume-hood for 30 min to allow all of the ethanol to completely evaporate.</li>
	<li>Take the clean, dry corrosion vessel and rinse it with the electrolyte that will be used for the corrosion run. For each rinse fill the corrosion vessel with 200 ml of the electrolyte and repeat this procedure 3 times. For this study, rinse the corrosion vessel with phosphate buffered saline (PBS). The chemical make-up of the PBS (10 L) electrolyte used throughout is 80 g NaCl, 11.5 g Na2HPO4, 2 g KCl and 2 g KHPO4.</li>
	<li>Following the rinse, fill the corrosion vessel with the required volume of PBS ready for the reaction.</li>
</ol>
3. Setup of Apparatus
<ol>
	<li>Clamp a heater with an inbuilt circulation system to the side of the outer compartment using a clamp. The size of the outer compartment needs to be approximately 30 cm x 20 cm x 20 cm and made of either glass or polymeric to be capable of housing the smaller corrosion vessel and the heater system.</li>
	<li>Fill the outer compartment with tap water until the level of water is higher than the height of the suspended electrodes within the corrosion vessel. The smaller compartment is the corrosion vessel (previously described in section 2).</li>
	<li>Seal the corrosion vessel with a glass reaction lid and clamp to ensure a waterproof seal. The lid of the chamber provides six entry points for experimental and measurement apparatus.</li>
	<li>Suspend a thermometer from one of the entry points of the reaction lid to provide a reading of the temperature within the corrosion cell. Suspend all three electrodes from the lid using the other 3 entry points. Use polytetrafluoroethylene (PTFE) tape to secure the seal of each connection.</li>
	<li>Use a three-electrode configuration consisting of a reference, counter, and working electrode. The working electrode is the stainless steel screw (specimen under analysis). Before inserting the electrode into the corrosion vessel, wipe with an 80% ethanol soaked wipe and place in a glass beaker filled with 100 ml of PBS.</li>
	<li>Use a connection pin to attach the electrode holders onto the electrode suspenders. Fit the electrode suspenders into the entry points of the corrosion vessel&#39;s lid.</li>
	<li>Place the working electrode centrally with the counter and reference electrode being suspended from either side. Seal the glass entry point and the corrosion suspenders using PTFE tape.</li>
	<li>For the reference electrode, use a standard Ag/AgCl. For the counter electrode, use a platinum mesh that was loosely bent to wrap around the specimen under test (working electrode).</li>
	<li>Fill the Ag/AgCl electrode with 3 M KCl using a pipette. Following extensive use, change and refill the Ag Ag/Cl. To do this release the tip of the electrode to empty out the fluid into a small glass collection vessel (beaker). Once all the solution is removed insert the tip and fill with 3 M KCl.</li>
	<li>Use tape on all junctions to ensure the whole chamber is sealed.</li>
	<li>Once the chamber is sealed with all electrodes placed inside the corrosion vessel, set the temperature to 37 &#176;C and open the nitrogen valve with a flow rate of 150 cm3/min. Leave the temperature and nitrogen running for 60 min before conducting a run. Keep nitrogen running for the duration of the experiment.</li>
</ol>
4. Running Corrosion Test
<ol>
	<li>Open the electrochemical software package, which interfaces with the USB controlled potentiostat.</li>
	<li>Make electrical connections between the potentiostat and the 3 electrodes and then turn the potentiostat on.</li>
	<li>Open and use the &#34;measurement view&#34; to view the potential and current readings of corrosion environment. During the open circuit potential (OCP) phase where no ramp potential is yet applied the current reading between the working (positive potential) and counter (negative) electrode is around (0 &#177; 0.01) &#181;A. The improper sealing of the chamber with PTFE tape can cause fluctuations in the current reading due to the chamber being aerated with nitrogen gas to remove oxygen molecules.</li>
	<li>Leave the sample to equilibrate and stabilize within the corrosion vessel environment. The time duration for this varies (1 to 6 hr) and is dependent on material. Monitor the potential using measurement view to determine if stabilized conditions are reached. The potential will be constant with no fluctuations when stable conditions are reached.</li>
	<li>After stable conditions are reached, start the corrosion run. However before this can be done, fill in the &#34;corrosion program&#34; and &#34;cyclic voltammetry (CV)&#34; conditions using the skeleton template provided by analytical software.</li>
	<li>Select the cyclic voltammetry potentiostat procedure within the setup view from the procedure tab.</li>
	<li>Enable the following parameters to be sampled for the corrosion run: the time, working electrode (WE) potential, and current for the corrosion run.</li>
	<li>Select the option to automate the current range. Set the highest current in the range to be 10 mA, and the lowest current in the range to be 10 nA for the WE.</li>
	<li>Ensure the final cut-off selection is controlled through the potential by setting the &#39;cycle back&#39; parameter to 0.8 mV to allow the hysteresis loop to complete.</li>
	<li>Record the OCP from the measurement view into the OCP parameter text box. Set the start potential 100 mV below the recorded OCP value. Set the upper vertex potential to 800 mV, the lower vertex to 100 mV below the start potential and the stop potential to 100 mV below the lower vertex potential. Set the scan rate to 0.001 V/sec and the step potential to 0.0024 V/sec. Now Press start.</li>
</ol>
5. After the Completion of the Corrosion Run
Note: After the completion of the corrosion run the polarization scan is shown within the analysis view of the software. For each polarization run the presenter view lists the OCP, the plot for E vs. t and the CV staircase which is a plot of E vs. Log (i).
<ol>
	<li>Within each plot link, determine internal filtration of the data points, Tafel extrapolation, and plot options. Expand each link presented to show various parameters of interest, which collectively form the electrochemical parameters. The polarization scan (current density vs. potential), determines the open circuit potential, pitting potential (Epit) and the protection potential (Epro).</li>
	<li>Tabulate the anodic and cathodic Tafel constants, the corrosion rate, the corrosion current, corrosion current density, the start potential, and end potential under the corrosion rate using the Tafel slope link.</li>
</ol>
6. Removing the Sample from the Electrode Holder
<ol>
	<li>Prepare 3 small jars of 50 ml with dichloromethane under the fume hood.</li>
	<li>Remove tested samples from the electrode holders by immersing the lower end of the holder in dichloromethane for 30 min inside a fume-hood.</li>
	<li>Once detached, place the specimen into the next jar of dichloromethane and leave for 15 min. Repeat this process with the third and final rinse to get rid of any excess coating on the attachment sections of the sample.</li>
	<li>Wipe the remaining sealant from the clip and sample and finally rinse with DI water.</li>
</ol>

<ol>
	<li>Isaacs, H. S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Aspects+of+corrosion+from+the+ECS+Publications.">Aspects of corrosion from the ECS Publications.</a> J. Electrochem. Soc. 149 (12), 85-87 (2002).</li><li>Fontana, M. G., Greene, N. D. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=.">.</a> Corrosion Engineering. , (1978).</li><li>Pourbaix, M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Electrochemical+corrosion+of+metallic+biomaterials.">Electrochemical corrosion of metallic biomaterials.</a> Biomaterials. 5 (3), 122-134 (1984).</li><li>Rechnitz, G. A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=.">.</a> Controlled-Potential Analysis. , (1963).</li><li>Silverman, D. C., Revie, R. W. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Chapter+68.">Chapter 68.</a> Uhlig's Corrosion Handbook. , (2000).</li><li>Gurappa, I. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Characterization+of+different+materials+for+corrosion+resistance+under+simulated+body+fluid+conditions.">Characterization of different materials for corrosion resistance under simulated body fluid conditions.</a> Mater Charact. 49 (1), 73-79 (2002).</li><li>Antoniou, J., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Metal+ion+levels+in+the+blood+of+patients+after+hip+resurfacing:+a+comparison+between+twenty-eight+and+thirty-six-millimeter-head+metal-on-metal+prostheses.">Metal ion levels in the blood of patients after hip resurfacing: a comparison between twenty-eight and thirty-six-millimeter-head metal-on-metal prostheses.</a> J Bone Joint Surg Am. 90, 142-148 (2008).</li><li>Billi, F., Campbell, P. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Nanotoxicology+of+metal+wear+particles+in+total+joint+arthroplasty:+a+review+of+current+concepts.">Nanotoxicology of metal wear particles in total joint arthroplasty: a review of current concepts.</a> J Appl Biomater Funct Mater. 8 (1), 1-6 (2010).</li><li>Bradberry, S. M., Wilkinson, J. M., Ferner, R. E. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Systemic+toxicity+related+to+metal+hip+prostheses.">Systemic toxicity related to metal hip prostheses.</a> Clin Toxicol (Phila). 52 (8), 837-847 (2014).</li><li>Davda, K., Lali, F. V., Sampson, B., Skinner, J. A., Hart, A. J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=An+analysis+of+metal+ion+levels+in+the+joint+fluid+of+symptomatic+patients+with+metal-on-metal+hip+replacements.">An analysis of metal ion levels in the joint fluid of symptomatic patients with metal-on-metal hip replacements.</a> J Bone Joint Surg Br. 93 (6), 738-745 (2011).</li><li>Clarke, M. T., Lee, P. T., Arora, A., Villar, R. N. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Levels+of+metal+ions+after+small+and+large+diameter+metal-on-metal+hip+arthroplasty.">Levels of metal ions after small and large diameter metal-on-metal hip arthroplasty.</a> J Bone Joint Surg Br. 85 (6), 913-917 (2003).</li><li>Brown, S. A., Hughes, P. J., Merritt, K. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=In+vitro+studies+of+fretting+corrosion+of+orthopaedic+materials.">In vitro studies of fretting corrosion of orthopaedic materials.</a> J Orthop Res. 6 (4), 572-579 (1988).</li><li>Bryant, M., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Characterisation+of+the+surface+topography,+tomography+and+chemistry+of+fretting+corrosion+product+found+on+retrieved+polished+femoral+stems.">Characterisation of the surface topography, tomography and chemistry of fretting corrosion product found on retrieved polished femoral stems.</a> J Mech Behav Biomed Mater. 32, 321-334 (2014).</li><li>Jantzen, C., J&#248;rgensen, H. L., Duus, B. R., Sporring, S. L., Lauritzen, J. B. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Chromium+and+cobalt+ion+concentrations+in+blood+and+serum+following+various+types+of+metal-on-metal+hip+arthroplasties.+A+literature+review.">Chromium and cobalt ion concentrations in blood and serum following various types of metal-on-metal hip arthroplasties. A literature review.</a> Acta Orthopaedica. 84 (3), 229-236 (2013).</li><li>Campbell, P., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Histological+Features+of+Pseudotumor-like+Tissues+From+Metal-on-Metal+Hips.">Histological Features of Pseudotumor-like Tissues From Metal-on-Metal Hips.</a> Clin. Orthop. Relat. Res. 468 (9), 2321-2327 (2010).</li><li>Cook, S. D., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+in+vivo+performance+of+250+internal+fixation+devices:+a+follow-up+study.">The in vivo performance of 250 internal fixation devices: a follow-up study.</a> Biomaterials. 8 (3), 177-184 (1987).</li><li>Cooper, H. J., Urban, R. M., Wixson, R. L., Meneghini, R. M., Jacobs, J. J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Adverse+local+tissue+reaction+arising+from+corrosion+at+the+femoral+neck-body+junction+in+a+dual-taper+stem+with+a+cobalt-chromium+modular+neck.">Adverse local tissue reaction arising from corrosion at the femoral neck-body junction in a dual-taper stem with a cobalt-chromium modular neck.</a> J Bone Joint Surg Am. 95 (10), 865-872 (2013).</li><li>Langton, D. J., Sprowson, A. P., Joyce, T. J., Reed, M., Carluke, I., Partington, P., Nargol, A. V. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Blood+metal+ion+concentrations+after+hip+resurfacing+arthroplasty.">Blood metal ion concentrations after hip resurfacing arthroplasty.</a> J Bone Joint Surg Br. 91 (10), 1287-1295 (2009).</li><li>Langton, D. J., Jameson, S. S., Joyce, T. J., Webb, J., Nargol, A. V. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+effect+of+component+size+and+orientation+on+the+concentrations+of+metal+ions+after+resurfacing+arthroplasty+of+the+hip.">The effect of component size and orientation on the concentrations of metal ions after resurfacing arthroplasty of the hip.</a> J Bone Joint Surg Br. 90 (9), 1143-1151 (2008).</li><li>Daniel, J., Ziaee, H., Pradhan, C., McMinn, D. J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Six-year+results+of+a+prospective+study+of+metal+ion+levels+in+young+patients+with+metal-on-metal+hip+resurfacings.">Six-year results of a prospective study of metal ion levels in young patients with metal-on-metal hip resurfacings.</a> J Bone Joint Surg Br. 91 (2), 176-179 (2009).</li><li>De Haan, R., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Correlation+between+inclination+of+the+acetabular+component+and+metal+ion+levels+in+metal-on-metal+hip+resurfacing+replacement.">Correlation between inclination of the acetabular component and metal ion levels in metal-on-metal hip resurfacing replacement.</a> J Bone Joint Surg Br. 90 (10), 1291-1297 (2008).</li><li>Dijkman, M. A., de Vries, I., Mulder-Spijkerboer, H., Meulenbelt, J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Cobalt+poisoning+due+to+metal-on-metal+hip+implants.">Cobalt poisoning due to metal-on-metal hip implants.</a> Ned Tijdschr Geneeskd. 156 (42), A4983 (2012).</li><li>Fisher, J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Bioengineering+reasons+for+the+failure+of+metal-on-metal+hip+prostheses:+an+engineer's+perspective.">Bioengineering reasons for the failure of metal-on-metal hip prostheses: an engineer's perspective.</a> J Bone Joint Surg Br. 93 (8), 1001-1004 (2011).</li><li>Goldberg, J. R., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=A+Multicenter+Retrieval+Study+of+the+Taper+Interfaces+of+Modular+Hip+Prostheses.">A Multicenter Retrieval Study of the Taper Interfaces of Modular Hip Prostheses.</a> Clin. Orthop. Relat. Res. (401), 149-161 (2002).</li><li>Ingham, E., Fisher, J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Biological+reactions+to+wear+debris+in+total+joint+replacement.">Biological reactions to wear debris in total joint replacement.</a> Proc Inst Mech Eng H. 214 (1), 21-37 (2000).</li><li>Gilbert, J. L., Buckley, C. A., Jacobs, J. J., Res, J. .. B. i. o. m. e. d. .. M. a. t. e. r. .. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=In+vivo+corrosion+of+modular+hip+prosthesis+components+in+mixed+and+similar+metal+combinations.+The+effect+of+crevice,+stress,+motion+and+allot+coupling.">In vivo corrosion of modular hip prosthesis components in mixed and similar metal combinations. The effect of crevice, stress, motion and allot coupling.</a> J. Biomed. Mater. Res. 76 (1), 1533-1544 (1993).</li><li>Browne, J. A., Bechtold, C. D., Berry, D. J., Hanssen, A. D., Lewallen, D. G. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Failed+metal-on-metal+hip+arthroplasties:+a+spectrum+of+clinical+presentations+and+operative+findings.">Failed metal-on-metal hip arthroplasties: a spectrum of clinical presentations and operative findings.</a> Clin. Orthop. Relat. Res. 468 (9), 2313-2320 (2010).</li><li>Jantzen, C., Jorgensen, H. L., Duus, B. R., Sporring, S. L., Lauritzen, J. B. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Chromium+and+cobalt+ion+concentrations+in+blood+and+serum+following+various+types+of+metal-on-metal+hip+arthroplasties:+a+literature+overview.">Chromium and cobalt ion concentrations in blood and serum following various types of metal-on-metal hip arthroplasties: a literature overview.</a> Acta Orthop. 84 (3), 229-236 (2013).</li><li>Frangini, S., De Cristofaro, N. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Analysis+of+galvanostatic+polarisation+method+for+determining+reliable+pitting+potentials+on+stainless+steels+in+crevice-free+conditions.">Analysis of galvanostatic polarisation method for determining reliable pitting potentials on stainless steels in crevice-free conditions.</a> Corros Sci. 45 (12), 2769-2786 (2002).</li></ol>

The authors have nothing to disclose.

Polarization scans produced from the stainless steel samples showed clean continuous plots correlating with scans seen in literature indicative of a well functioning corrosion system which is both reliable and reproducible 29. Poor reproducibility of potentiodynamic pitting potentials is identified with a spread of a few hundred millivolts, with pitting potential being characterized by a stochastic process 29. This is commonly due to the variables of temperature, halide content and potential (V); th...

Electrochemical techniques provide a quick and relatively inexpensive method to obtain the electrochemical properties of a material. These techniques are based predominately on the ability to detect corrosion of a metal by observing the response of the charge-transfer process to a controlled electrochemical disturbance 1-5. Corrosion of metal implants within a body environment is critical due to the adverse implications on biocompatibility and material integrity 6. The main factor contributing to corrosion of implants within the body is the dissolution of the surface oxide leading to an increased release of metallic ions 7-11. This results in adverse biological reactions, which can be found locally, but with potentially systemic effects leading to the premature failure of the implant 10,12-28.
The corrosion characteristics of a test specimen are predicted from the polarization scan produced by a potentiostat. A polarization scan allows for the extrapolation of the kinetic and corrosion parameters of a metal substrate. During a scan, the oxidation or reduction of an electro-active species can be limited by charge transfer and the movement of reactants or products. These factors are all encapsulated by the polarization scan; therefore the importance of having a system that produces a reliable and repeatable polarization scan across multiple cycles is of great importance. The main focus of this manuscript is to provide a protocol identifying the rationale and steps taken to obtain a well-functioning potentiodynamic corrosion system.

<table><tbody><tr><td>Potentiostat</td><td>Metrohm</td><td>PGSTAT101</td><td></td></tr><tr><td>Ag/AgCl reference electrode, shielded</td><td>Metrohm</td><td>6.0729.100</td><td></td></tr><tr><td>Electrode shaft</td><td>Metrohm</td><td>6.1241.060</td><td></td></tr><tr><td>Polisher Forcipol 1v</td><td>Metkon</td><td>3602</td><td></td></tr><tr><td>Clindrical flask 700 ml</td><td>SciLabware</td><td>FR700F</td><td></td></tr><tr><td>Reaction lid</td><td>SciLabware</td><td>MAF2/41</td><td></td></tr><tr><td>Dichloromethane</td><td>Sigma-Aldrich</td><td>MKBR7629V</td><td>Use under a fumehood. Wear protective clothing.</td></tr><tr><td>Thermo / HAAKE D Series Immersion Circulators</td><td>Haake</td><td></td><td></td></tr></tbody></table>

potentiodynamic corrosion testing

Different metallic materials have different polarization characteristics as dictated by the open circuit potential, breakdown potential, and passivation potential of the material. The detection of these electrochemical parameters identifies the corrosion factors of a material. A reliable and well-functioning corrosion system is required to achieve this.
Corrosion of the samples was achieved via a potentiodynamic polarization technique employing a three-electrode configuration, consisting of reference, counter, and working electrodes. Prior to commencement a baseline potential is obtained. Following the stabilization of the corrosion potential (Ecorr), the applied potential is ramped at a slow rate in the positive direction relative to the reference electrode. The working electrode was a stainless steel screw. The reference electrode was a standard Ag/AgCl. The counter electrode used was a platinum mesh. Having a reliable and well-functioning in vitro corrosion system to test biomaterials provides an in-expensive technique that allows for the systematic characterization of the material by determining the breakdown potential, to further understand the material's response to corrosion. The goal of the protocol is to set up and run an in vitro potentiodynamic corrosion system to analyze pitting corrosion for small metallic medical devices.

At the conclusion of the procedure an in vitro corrosion system is setup to conduct corrosion studies. Specific procedures such as the cleaning of the corrosion vessel and the Faraday cage were introduced into the protocol to improve noise performance. The fundamental concept of a good polarization scan is to identify the electro-physical conditions of the material providing valuable information in order to understand the corrosion susceptibility of a metallic material. The proce...

Watch this Scientific Journal Video about Potentiodynamic Corrosion Testing at JoVE.com

Potentiodynamic Corrosion Testing

Here, we present a protocol to set up and run an in vitro potentiodynamic corrosion system to analyze pitting corrosion for small metallic medical devices.

Different metallic materials have different polarization characteristics as dictated by the open circuit potential, breakdown potential, and passivation ...

Universidad San Sebastian

Research

JoVE Journal

Environment

17.5K Views.  Prince of Wales Clinical School. Here, we present a protocol to set up and run an in vitro potentiodynamic corrosion system to analyze pitting corrosion for small metallic medical devices. 

Video: Potentiodynamic Corrosion Testing

Metal Corrosion and the Efficiency of Corrosion Inhibitors in Less Conductive Media

Material corrosion can be a limiting factor for different materials in many applications. Thus, it is necessary to better understand corrosion processes, prevent them and minimize the damages associated with them. One of the most important characteristics of corrosion processes is the corrosion rate. The measurement of corrosion rates is often very difficult or even impossible especially in less conductive, non-aqueous environments such as biofuels. Here, we present five different methods for the determination of corrosion rates and the efficiency of anti-corrosion protection in biofuels: (i) a static test, (ii) a dynamic test, (iii) a static test with a reflux cooler and electrochemical measurements (iv) in a two-electrode arrangement and (v) in a three-electrode arrangement. The static test is advantageous due to its low demands on material and instrumental equipment. The dynamic test allows for the testing of corrosion rates of metallic materials at more severe conditions. The static test with a reflux cooler allows for the testing in environments with higher viscosity (e.g., engine oils) at higher temperatures in the presence of oxidation or an inert atmosphere. The electrochemical measurements provide a more comprehensive view on corrosion processes. The presented cell geometries and arrangements (the two-electrode and three-electrode systems) make it possible to perform measurements in biofuel environments without base electrolytes that could have a negative impact on the results and load them with measurement errors. The presented methods make it possible to study the corrosion aggressiveness of an environment, the corrosion resistance of metallic materials, and the efficiency of corrosion inhibitors with representative and reproducible results. The results obtained using these methods can help to understand corrosion processes in more detail to minimize the damages caused by corrosion.

The testing of processes associated with material corrosion can often be difficult especially in non-aqueous environments. Here, we present different methods for short-term and long-term testing of corrosion behavior of non-aqueous environments such as biofuels, especially those containing bioethanol.

Material corrosion can be a limiting factor for different materials in many applications. Thus, it is necessary to better understand corrosion processes, ...

Electrochemical Impedance Spectroscopy as a Tool for Electrochemical Rate Constant Estimation

Electrochemical impedance spectroscopy (EIS) was used for advanced characterization of organic electroactive compounds along with cyclic voltammetry (CV). In the case of fast reversible electrochemical processes, current is predominantly affected by the rate of diffusion, which is the slowest and limiting stage. EIS is a powerful technique that allows separate analysis of stages of charge transfer that have different AC frequency response. The capability of the method was used to extract the value of charge transfer resistance, which characterizes the rate of charge exchange on the electrode-solution interface. The application of this technique is broad, from biochemistry up to organic electronics. In this work, we are presenting the method of analysis of organic compounds for optoelectronic applications.

Electrochemical impedance spectroscopy (EIS) of species that undergo reversible oxidation or reduction in solution was used for determination of rate constants of oxidation or reduction.

Electrochemical impedance spectroscopy (EIS) was used for advanced characterization of organic electroactive compounds along with cyclic voltammetry (CV). ...

Chemistry

Synthesis of Platinum-nickel Nanowires and Optimization for Oxygen Reduction Performance

Platinum-nickel (Pt-Ni) nanowires were developed as fuel cell electrocatalysts, and were optimized for the performance and durability in the oxygen reduction reaction. Spontaneous galvanic displacement was used to deposit Pt layers onto Ni nanowire substrates. The synthesis approach produced catalysts with high specific activities and high Pt surface areas. Hydrogen annealing improved Pt and Ni mixing and specific activity. Acid leaching was used to preferentially remove Ni near the nanowire surface, and oxygen annealing was used to stabilize near-surface Ni, improving durability and minimizing Ni dissolution. These protocols detail the optimization of each post-synthesis processing step, including hydrogen annealing to 250 &#176;C, exposure to 0.1 M nitric acid, and oxygen annealing to 175 &#176;C. Through these steps, Pt-Ni nanowires produced increased activities more than an order of magnitude than Pt nanoparticles, while offering significant durability improvements. The presented protocols are based on Pt-Ni systems in the development of fuel cell catalysts. These techniques have also been used for a variety of metal combinations, and can be applied to develop catalysts for a number of electrochemical processes.

&#160; The protocol describes the synthesis and electrochemical testing of platinum-nickel nanowires. Nanowires were synthesized by the galvanic displacement of a nickel nanowire template. Post-synthesis processing, including hydrogen annealing, acid leaching, and oxygen annealing were used to optimize nanowire performance and durability in the oxygen reduction reaction.

Platinum-nickel (Pt-Ni) nanowires were developed as fuel cell electrocatalysts, and were optimized for the performance and durability in the oxygen ...

Experimental Protocol to Determine the Chloride Threshold Value for Corrosion in Samples Taken from Reinforced Concrete Structures

The aging of reinforced concrete infrastructure in developed countries imposes an urgent need for methods to reliably assess the condition of these structures. Corrosion of the embedded reinforcing steel is the most frequent cause for degradation. While it is well known that the ability of a structure to withstand corrosion depends strongly on factors such as the materials used or the age, it is common practice to rely on threshold values stipulated in standards or textbooks. These threshold values for corrosion initiation (Ccrit) are independent of the actual properties of a certain structure, which clearly limits the accuracy of condition assessments and service life predictions. The practice of using tabulated values can be traced to the lack of reliable methods to determine Ccrit on-site and in the laboratory.
Here, an experimental protocol to determine Ccrit for individual engineering structures or structural members is presented. A number of reinforced concrete samples are taken from structures and laboratory corrosion testing is performed. The main advantage of this method is that it ensures real conditions concerning parameters that are well known to greatly influence Ccrit, such as the steel-concrete interface, which cannot be representatively mimicked in laboratory-produced samples. At the same time, the accelerated corrosion test in the laboratory permits the reliable determination of Ccrit prior to corrosion initiation on the tested structure; this is a major advantage over all common condition assessment methods that only permit estimating the conditions for corrosion after initiation, i.e., when the structure is already damaged.
The protocol yields the statistical distribution of Ccrit for the tested structure. This serves as a basis for probabilistic prediction models for the remaining time to corrosion, which is needed for maintenance planning. This method can potentially be used in material testing of civil infrastructures, similar to established methods used for mechanical testing.

We propose a method to measure a parameter that is highly relevant for corrosion assessments or predictions of reinforced concrete structures, with the main advantage of permitting testing of samples from engineering structures. This ensures real conditions at the steel-concrete interface, which are crucial to avoid artifacts of laboratory-made samples.

The aging of reinforced concrete infrastructure in developed countries imposes an urgent need for methods to reliably assess the condition of these ...

Engineering

Determination of Thermodynamic Properties of Alkaline Earth-liquid Metal Alloys Using the Electromotive Force Technique

A novel electrochemical cell based on a CaF2 solid-state electrolyte has been developed to measure the electromotive force (emf) of binary alkaline earth-liquid metal alloys as functions of both composition and temperature in order to acquire thermodynamic data. The cell consists of a chemically stable solid-state CaF2-AF2 electrolyte (where A is the alkaline-earth element such as Ca, Sr, or Ba), with binary A-B alloy (where B is the liquid metal such as Bi or Sb) working electrodes, and a pure A metal reference electrode. Emf data are collected over a temperature range of 723 K to 1,123 K in 25 K increments for multiple alloy compositions per experiment and the results are analyzed to yield activity values, phase transition temperatures, and partial molar entropies/enthalpies for each composition.

This protocol describes the measurement of the electromotive force of alkaline-earth elements in liquid metal alloys at high temperatures (723-1,123 K) to determine their thermodynamic properties, including activity, partial molar entropy, partial molar enthalpy, and phase transition temperatures, over a wide composition range.

A novel electrochemical cell based on a CaF2 solid-state electrolyte has been developed to measure the electromotive force (emf) of binary alkaline ...

Applicability Analysis of Assessment Methods for Morphological Parameters of Corroded Steel Bars

The irregular and uneven residual sections along the length of a corroded steel bar substantially change its mechanical properties and significantly dominate the safety and performance of an existing concrete structure. As a result, it is important to measure the geometry and amount of corrosion of a steel bar in a structure properly to assess the residual bearing capacity and service life of the structure. This paper introduces and compares five different methods for measuring the geometry and amount of corrosion of a steel bar. A single 500 mm long and 14 mm diameter steel bar is the specimen that is subjected to accelerated corrosion in this protocol. Its morphology and the amount of corrosion were carefully measured before and after using mass loss measurements, a Vernier caliper, drainage measurements, 3D scanning, and X-ray micro-computed tomography (XCT). The applicability and suitability of these different methods were then evaluated. The results show that the Vernier caliper is the best choice for measuring the morphology of a non-corroded bar, while 3D scanning is the most suitable for quantifying the morphology of a corroded bar.

This paper measures the geometry and the amount of corrosion of a steel bar using different methods: mass loss, calipers, drainage measurements, 3D scanning, and X-ray micro-computed tomography (XCT).

The irregular and uneven residual sections along the length of a corroded steel bar substantially change its mechanical properties and significantly ...

Determining Tribocorrosion Rate and Wear-Corrosion Synergy of Bulk and Thin Film Aluminum Alloys

The increasing complexity and severity of service conditions in areas, such as aerospace and marine industries, nuclear systems, microelectronics, batteries, and biomedical devices, etc., impose great challenges on the reliable performance of alloys exposed to extreme conditions where mechanical and electrochemical attack co-exist. Finding ways for alloys to mitigate the combined attack of wear and corrosion (i.e., tribocorrosion) under such extreme conditions is thus highly critical for improving their reliability and service lifetime when used in such conditions. The challenge lies in the fact that wear and corrosion are not independent of each other, but rather work synergistically to accelerate the total material loss. Thus, a reliable method to evaluate the tribocorrosion resistance of metals and alloys is needed. Here, a protocol for measuring the tribocorrosion rate and wear-corrosion synergy of Al-based bulk and thin film samples in a corrosive environment under room temperature is presented.

Here, we present a protocol to measure the tribocorrosion rate and wear-corrosion synergy of thin film and bulk Al alloys in simulated sea water at room temperature.

The increasing complexity and severity of service conditions in areas, such as aerospace and marine industries, nuclear systems, microelectronics, ...

Electrochemical Roughening of Thin-Film Platinum Macro and Microelectrodes

This protocol demonstrates a method for electrochemical roughening of thin-film platinum electrodes without preferential dissolution at grain boundaries of the metal. Using this method, a crack free, thin-film macroelectrode surface with up to 40 times increase in active surface area was obtained. The roughening is easy to do in a standard electrochemical characterization laboratory and incudes the application of voltage pulses followed by extended application of a reductive voltage in a perchloric acid solution. The protocol includes the chemical and electrochemical preparation of both a macroscale (1.2 mm diameter) and microscale (20 &#181;m diameter) platinum disc electrode surface, roughening the electrode surface and characterizing the effects of surface roughening on electrode active surface area. This electrochemical characterization includes cyclic voltammetry and impedance spectroscopy and is demonstrated for both the macroelectrodes and the microelectrodes. Roughening increases electrode active surface area, decreases electrode impedance, increases platinum charge injection limits to those of titanium nitride electrodes of same geometry and improves substrates for adhesion of electrochemically deposited films.

This protocol demonstrates a method for electrochemical roughening of thin-film platinum electrodes without preferential dissolution at grain boundaries. The electrochemical techniques of cyclic voltammetry and impedance spectroscopy are demonstrated to characterize these electrode surfaces.

This protocol demonstrates a method for electrochemical roughening of thin-film platinum electrodes without preferential dissolution at grain boundaries ...

Applying Dynamic Strain on Thin Oxide Films Immobilized on a Pseudoelastic Nickel-Titanium Alloy

Direct alteration of material structure/function through strain is a growing area of research that has allowed for novel properties of materials to emerge. Tuning material structure can be achieved by controlling an external force imposed on materials and inducing stress-strain responses (i.e., applying dynamic strain). Electroactive thin films are typically deposited on shape or volume tunable elastic substrates, where mechanical loading (i.e., compression or tension) can affect film structure and function through imposed strain. Here, we summarize methods for straining n-type doped titanium dioxide (TiO2) films prepared by a thermal treatment of a pseudo-elastic nickel-titanium alloy (Nitinol). The main purpose of the described methods is to study how strain affects electrocatalytic activities of metal oxide, specifically hydrogen evolution and oxygen evolution reactions. The same system can be adapted to study the effect of strain more broadly. Strain engineering can be applied for optimization of a material function, as well as for design of adjustable, multifunctional (photo)electrocatalytic materials under external stress control.

Dynamic, tensile strain is applied on TiO2 thin films to study the effects of strain on electrocatalysis, specifically proton reduction and water oxidation. TiO2 films are prepared by thermal treatment of the pseudo-elastic NiTi alloy (Nitinol).

Direct alteration of material structure/function through strain is a growing area of research that has allowed for novel properties of materials to ...

Electrochemical Measurements of Supported Catalysts Using a Potentiostat/Galvanostat

Source: Laboratory of Dr. Yuriy Rom&#225;n &#8212; Massachusetts Institute of Technology
A potentiostat/galvanostat (often referred to as simply a potentiostat) is an instrument that measures current at an applied potential (potentiostatic operation) or measures potential at an applied current (galvanostatic operation) (Figure 1). It is the most commonly used instrument in the electrochemical characterization of anode and cathode materials for fuel cells, electrolyzers, batteries, and supercapacitors.
Conventionally, these anode and cathode materials are interfaced with a potentiostat via a three-electrode electrochemical cell. The electrode leads from the potentiostat are connected to the reference electrode, the counter electrode (often called the auxiliary electrode), and the working electrode (which contains the test material of interest). The electrochemical cell is then filled with a high ionic strength electrolyte solution, such as an acidic, alkaline, or salt solution. The media for this high ionic strength solution is typically aqueous; however, for applications necessitating higher operating cell potential windows, such as batteries and supercapacitors, non-aqueous media is often used. The cell media is degassed with an inert gas (to prevent unwanted side reactions) or with a test gas (if the test reaction involves a gas at one of the electrodes).
Alternatively, a salt bridge or membrane is employed to maintain ionic contact if the two half cells are to be measured in different electrolytes. In heterogeneous electrocatalysis, this type of &#34;two compartment&#34; cell is often used if the test molecule at the working electrode is also reactive at the counterelectrode. This happens frequently as the counterelectrode typically employed is platinum, which is a highly active catalyst for many reactions. Here, single compartment cells will be used, where all three electrodes are in the same media.
This video will explain the process of polishing a working electrode, preparing a catalyst ink, mounting the catalyst ink onto the working electrode, preparing the electrochemical cell, and then performing electrochemical measurements. The measurements that are performed include: cyclic voltammetry (CV), linear sweep voltammetry (LSV), chronopotentiometry (CP), and chronoamperometry (CA).
<img alt="Figure 1" src="/files/ftp_upload/5698/5698fig1.jpg" /> 
Figure 1. An example of a single compartment electrochemical cell. a.) Teflon cap, b.) glass cell, c.) Pt wire counter electrode, d.) working electrode, e.) Ag/AgCl reference electrode, f.) 0.5 M aqueous sulfuric acid electrolyte solution.