Name: metal corrosion and the efficiency of corrosion inhibitors in less conductive media
Uploaded: 2018-11-03T13:00:00.000+00:00
Duration: 10 min 5 s
Description: Watch this Scientific Journal Video about Metal Corrosion and the Efficiency of Corrosion Inhibitors in Less Conductive Media at JoVE.com

This research was funded from the institutional support for the long-term conceptual development of the research organization (company registration number CZ60461373) provided by the Ministry of Education, Youth and Sports, the Czech Republic, the Operational Programme Prague - Competitiveness (CZ.2.16/3.1.00/24501) and &#34;National Programme of Sustainability&#34; (NPU I LO1613) MSMT-43760/2015).

1. The Static Immersion Corrosion Test in Metal-Liquid Systems
<ol>
	<li>Add 100&#8211;150 mL of the tested liquid corrosion environment for testing the resistance of metallic materials or the efficiency of corrosion inhibitors (i.e., aggressive EGB contaminated with water and trace amounts of chlorides, sulfates and acetic acid) into a 250 mL bottle equipped with a hook for hanging an analyzed sample (Figure 1).</li>
	<li>Adjust the surface of the metallic samples by grinding using sandpaper (1200 mesh) and polishing under running water so that the surface is adjusted evenly. Then, degrease the sample surface thoroughly with about 25 mL of acetone and about 25 mL of ethanol, dry it freely or using pulp tissue, and weigh the sample on an analytical balance with an accuracy of four decimal places. 
	NOTE: The sample treatment must always be performed in the same manner, otherwise measurements can be loaded by an error. It is crucial to always use sandpaper with the same grain size and the used sandpapers must be disposable, i.e., one piece of sandpaper for each sample and measurement. The surface must be adjusted evenly, it cannot contain any surface defects such as scratches, pits, etc.</li>
	<li>After the surface treatment, hang the metallic sample into the liquid in the bottle so that it does not lie on the bottom of the bottle, see Figure 1. Close the bottle tightly enough to prevent liquid evaporation and air entry.</li>
	<li>Choose the volume of the tested liquid so that the liquid/metal surface ratio is about 10 cm3/1 cm2 minimally.</li>
	<li>At regular intervals, remove the metallic sample from the bottle, rinse it with about 25 mL of acetone, and use pulp tissue to dry it and remove the surface layer of excess corrosion products. Then, weigh the sample on an analytical balance with an accuracy of four decimal places. After weighing, return the sample back into the bottle. 
	NOTE: The intervals for removing and weighing the samples should be chosen individually for each tested sample based on a visual evaluation of the changes in the sample surface during the test. Shorter intervals (e.g., 8 h or less) should be applied when intensive surface changes are observed and the intervals can become longer (e.g., 24 h, 48 h) when less intensive or no surface changes are visible. When comparison between the samples is required, the test duration must be the same.</li>
	<li>From the weight of the metallic sample, calculate the weight loss from the beginning of the experiment related to the sample surface for the given exposure time. After steady state in the metal-liquid system occurs (no increase in the weight loss over time has been observed), terminate the experiment.</li>
	<li>Calculate the corrosion rate according to the procedure presented in Step 4 (before pickling) or in Step 5 (after pickling of the surface corrosion products). 
	NOTE: Corrosion rates obtained after pickling of the surface corrosion products are used for the evaluation of the efficiencies of corrosion inhibitors, for more details, see Representative Results.</li>
</ol>
2. The Dynamic Corrosion Test with Liquid Circulation
<ol>
	<li>Add 500 mL of the tested liquid corrosion environment into the four-necked flask of the storage part of the apparatus. Lubricate the ground glass joints of the flask with a silicone grease and fix (i) a reflux cooler, (ii) a thermometer, (iii) a suction capillary connected to a pump and (iv) the overflow connected to the tempered part on the necks of the flask according to Figure 2.</li>
	<li>Turn on the cryostat connected to the cooler and set the temperature to -40 &#176;C. Fill the closed cooling circuit with ethanol.</li>
	<li>Use the capillary for fuel pumping to connect the pump to the preheating spiral of the tempered part, which brings a preheated fuel via the bottom of the measuring cell. Turn on the pump and set the desired fuel flow rate (500 mL&#215;h-1). Turn on the thermostat of the tempered part and set the temperature to the desired value (40 &#176;C).</li>
	<li>Once the tempered part is filled with fuel and the fuel starts to flow via the overflow part back into the storage flask, open the measuring cell that consists of two parts connected via a ground glass joint and hang the ground, polished, degreased and weighed sample (metal sheet with appropriate proportions) on the hanger. 
	NOTE: The sample treatment is performed according to the procedure presented in Step 1.2.</li>
	<li>Connect the frit to the tube for air supply with a pressure vessel via a pressure regulator and a flowmeter and set the desired gas flow rate on the flowmeter (20&#8211;30 mL&#215;min-1).</li>
	<li>At regular intervals, remove the metallic sample from the tempered part and follow the instructions presented in Step 1.5.</li>
	<li>Follow the instructions presented in Steps 1.6 and 1.7.</li>
</ol>
3. The Static Immersion Corrosion Test with a Reflux Cooler in the Presence of Gaseous Medium
<ol>
	<li>Add 200&#8211;300 mL of the tested sample (e.g., tested engine oil containing an aggressive E100 fuel) into the tempered flask.</li>
	<li>Hang a ground, polished, degreased and weighed sample on the hook of the cooler. Lubricate the ground glass joint of the cooler with a silicone grease and fix the cooler into the flask. 
	NOTE: The sample treatment is performed according to the procedure presented in Step 1.2.</li>
	<li>Connect the frit to the tube for the air supply with a pressure vessel via a pressure regulator and a flowmeter and set the desired gas flow rate (80 mL&#215;min-1) on the flowmeter.</li>
	<li>Set the temperature to 80 &#176;C on the thermostat for flask tempering and to -40 &#176;C on the cryostat connected to the cooler.</li>
	<li>After an appropriate period (e.g., 14 days), remove the metallic sample from the apparatus and follow the instructions presented in Step 1.5.</li>
	<li>Follow the instructions presented in Steps 1.6 and 1.7.</li>
</ol>
4. Calculation of the Corrosion Rate from Weight Losses
<ol>
	<li>From the corrosion losses obtained according to the methods presented in Steps 1-3, calculate the value of the corrosion rate according to Equations 1 and 2. 
	<img alt="Equation 1" src="/files/ftp_upload/57757/57757eq1.jpg" />&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;(1) 
	<img alt="Equation 2" src="/files/ftp_upload/57757/57757eq2.jpg" />&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;(2) 
	where nPm is the corrosion rate in g&#183;m&#8722;2&#183;h&#8722;1, &#961; is the density of the metallic material in g&#183;cm&#8722;3, &#916;m is the average weight loss in g, S is the surface area of the metallic material in m2, and T is the time (in hours) from the beginning of the test to the removal of the metal plate for measurement.</li>
</ol>
5. Pickling of the Corrosion Products on the Metal Surface
<ol>
	<li>Pickle the corroded samples of mild steel in a 10 wt. % solution of chelaton III at 50 &#176;C for 5 min. Then, remove the sample from the solution, clean it using a brush under running water, rinse it with acetone, dry and weigh it. After that, put the sample back into the chelaton solution and repeat the procedure until a constant weight is obtained.</li>
	<li>Pickle the corroded samples from brass, bronze or copper in a 10 vol. % solution of sulfuric acid under nitrogen bubbling (to remove dissolved air oxygen) for 1 min. Then, remove the sample from the solution, clean it using a brush under running water, rinse it with acetone, dry and weigh it. After that, put the sample back into the acid solution and repeat the procedure until a constant weight is obtained.</li>
</ol>
6. Electrochemical Measurements in the Two-Electrode Arrangement
<ol>
	<li>Remove the electrode system from the measuring cell, unscrew it, adjust the surface of the electrodes according to the procedure presented in Step 1.2 (without weighing) and then complete the electrode system again.</li>
	<li>Fill the measuring cell with 80 mL of the tested liquid corrosion environment and close it through the electrode system. Put the whole cell into a grounded Faraday cage. Connect the galvanostat and potentiostat to the electrode system so that one electrode of the system acts as a reference electrode and the second electrode acts as a working and an auxiliary electrode at the same time.</li>
	<li>In the instrument software, set the sequence containing the open circuit potential measurements (OCP, stabilization of corrosion potential in an open circuit) and the electrochemical impedance spectroscopy (EIS) measurement. The stabilization perform for at least 30 min to minimize the potential change.</li>
	<li>Undertake the EIS measurements at sufficiently high amplitude according to the conductivity of corrosion environment (fuel). 
	NOTE: The lower the fuel conductivity is, the higher amplitude values are needed. For fuels containing more than 80 vol. % of ethanol, choose the amplitude values in the range of 5&#8211;10 mV. For fuels containing ethanol in the range of 10&#8211;80 vol. %, choose the amplitude values in the range of 10&#8211;50 mV. For fuels containing less than 10 vol. % of ethanol, choose the amplitude values in the range of 50&#8211;80 mV.</li>
	<li>Undertake the impedance measurements in a sufficient range of frequencies (1&#8211;5 mHz) to be able to evaluate the low- and also high-frequency parts of the spectra.</li>
	<li>Determine the cell constant Ks for each electrode by measurement in n-heptane, which has a permittivity of about 1.92 according to the following equation: 
	<img alt="Equation 3" src="/files/ftp_upload/57757/57757eq3.jpg" />&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;(3) 
	where C is the capacitance obtained from the high-frequency part of the impedance spectrum measured in a planar electrode arrangement in the n-heptane-metal system, &#949;r is the relative permittivity of n-heptane, and &#949;0 is the relative permittivity of the vacuum.</li>
	<li>Use the obtained cell constant for the calculation of the fuel permittivity &#949; and for the recalculation of the resistivity R according to the following equations: 
	<img alt="Equation 4" src="/files/ftp_upload/57757/57757eq4.jpg" />&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;(4) 
	<img alt="Equation 5" src="/files/ftp_upload/57757/57757eq5.jpg" />&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;(5)</li>
</ol>
7. Electrochemical Measurements in the Three-Electrode Arrangement
<ol>
	<li>Adjust the measuring part of the working electrode from the tested metallic material according to the procedure presented in Step 1.2 (without weighing) and screw it onto the electrode extension.</li>
	<li>Fill the measuring cell with 100 mL of the tested liquid corrosion environment and close it with a cap through which the working electrode from the tested material and the auxiliary electrode from the platinum wire are led. Twist the wire, i.e., auxiliary electrode, evenly around the working electrode. Through the side entry of the cell, insert the reference electrode with a bridge so that it is as close to the working electrode as possible. 
	NOTE: Electrodes cannot touch each other.</li>
	<li>Insert the cell into a grounded Faraday cell and connect the electrodes via a cable system to the galvanostat and potentiostat equipped with the appropriate software.</li>
	<li>In the software of the used measuring devices, set the measuring sequence containing the measurement of (i) the OCP for a sufficiently long time period (at least 60 min), (ii) the EIS in the range of about 1 MHz&#8211;1 mHz at an amplitude value of 5&#8211;20 mV and (iii) the polarization characteristics (Tafel scan) in the range of 200&#8211;500 mV to the corrosion potential.</li>
	<li>Calculate the current density jcorr according to the Stern-Geary equation: 
	<img alt="Equation 6" src="/files/ftp_upload/57757/57757eq6.jpg" />&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;(6) 
	<img alt="Equation 7" src="/files/ftp_upload/57757/57757eq7.jpg" />&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;(7) 
	where jcorr is the corrosion current density, ba and bk are Tafel constants, and Rp is the polarization resistance estimated from the EIS measurements. Furthermore, calculate the instantaneous corrosion rate from the material weight losses. Determine the material weight losses from the current density from Faraday&#180;s law as follows: 
	<img alt="Equation 8" src="/files/ftp_upload/57757/57757eq8.jpg" />&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;(8) 
	<img alt="Equation 9" src="/files/ftp_upload/57757/57757eq9.jpg" />&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;(9) 
	where m is the mass of the substance in g; I is the current; t is the time; A is the proportionality constant designated as the electrochemical equivalent of the substance, measured in kg&#183;C&#8722;1; F is the Faraday constant (9.6485 &#215; 104 C&#183;mol&#8722;1); and z is the number of electrons needed to exclude one molecule.22</li>
</ol>
8. Calculation of the Efficiency of Corrosion Inhibitors
<ol>
	<li>Use the obtained values of polarization resistance or corrosion rate to calculate the efficiency of the corrosion inhibitors according to the following equations: 
	<img alt="Equation 10" src="/files/ftp_upload/57757/57757eq10.jpg" />&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;(10) 
	or 
	<img alt="Equation 11" src="/files/ftp_upload/57757/57757eq11.jpg" />&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;(11) 
	where Ef is the efficiency of corrosion inhibitors in %; Ri is the polarization resistance of material; nI is the corrosion rate of material in a metal-fuel system containing the corrosion inhibitor; R0 is the polarization resistance; n0 is the corrosion rate in the metal-fuel system without the corrosion inhibitor.</li>
</ol>

<ol>
	<li>Revie, R. W., Uhlig, H. H. <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 and corrosion control: An Introduction to corrosion science and engineering, 4th edition. , (2008).</li><li>Edwards, R., Mahieu, V., Griesemann, J. -. C., Lariv&#233;, J. -. F., Rickeard, 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=Well-to-wheels+analysis+of+future+automotive+fuels+and+powertrains+in+the+European+context.+Report+No.+0148-7191.">Well-to-wheels analysis of future automotive fuels and powertrains in the European context. Report No. 0148-7191.</a> SAE Technical Paper. , (2004).</li><li>. Directive 2009/28/ES. On the promotion of the use of energy from renewable rources and amending and subsequently repealing Directives 2001/77/EC and 2003/77/EC Available from: <a target="_blank" href="https://eur-lex.europa.eu/legal-content/EN/ALL/?uri=celex%3A32009L0028">https://eur-lex.europa.eu/legal-content/EN/ALL/?uri=celex%3A32009L0028</a> (2009)</li><li>Tshiteya, R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=.">.</a> Properties of alcohol transportation fuels. , (1991).</li><li>Battino, R., Rettich, T. R., Tominaga, T. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+solubility+of+oxygen+and+ozone+in+liquids.">The solubility of oxygen and ozone in liquids.</a> Journal of Physical and Chemical Reference Data. 12 (2), 163-178 (1983).</li><li>Hsieh, W. -. D., Chen, R. -. H., Wu, T. -. L., Lin, T. -. H. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Engine+performance+and+pollutant+emission+of+an+SI+engine+using+ethanol-gasoline+blended+fuels.">Engine performance and pollutant emission of an SI engine using ethanol-gasoline blended fuels.</a> Atmospheric Environment. 36 (3), 403-410 (2002).</li><li>Pereira, R. C., Pasa, V. M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Effect+of+mono-olefins+and+diolefins+on+the+stability+of+automotive+gasoline.">Effect of mono-olefins and diolefins on the stability of automotive gasoline.</a> Fuel. 85 (12), 1860-1865 (2006).</li><li>Schweitzer, P. 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> Fundamentals of corrosion: mechanisms, causes, and preventative methods. , (2009).</li><li>Migahed, M., Al-Sabagh, A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Beneficial+role+of+surfactants+as+corrosion+inhibitors+in+petroleum+industry:+a+review+article.">Beneficial role of surfactants as corrosion inhibitors in petroleum industry: a review article.</a> Chemical Engineering Communications. 196 (9), 1054-1075 (2009).</li><li>Mac&#225;k, J., #268;ernou&#353;ek, T., Ji&#345;&#237;&#269;ek, I., Baro&#353;, P., Tom&#225;&#353;ek, J., Posp&#237;&#353;il, M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Elektrochemick&#233;+korozn&#237;+testy+v+kapaln&#253;ch+biopalivech+(Electrochemical+Corrosion+Tests+in+Liquid+Biofuels)+(in+Czech).">Elektrochemick&#233; korozn&#237; testy v kapaln&#253;ch biopalivech (Electrochemical Corrosion Tests in Liquid Biofuels) (in Czech).</a> Paliva. 1 (1), 1-4 (2009).</li><li>Nesic, S., Schubert, A., Brown, B. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Thin+channel+corrosion+flow+cell.">Thin channel corrosion flow cell.</a> International patent. , (2009).</li><li>Blum, S. C., Sartori, G., Robbins, W. K., Monette, L. M. -. A., Vogel, A., Yeganeh, M. S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Process+for+assessing+inhibition+of+petroleum+corrosion.">Process for assessing inhibition of petroleum corrosion.</a> International Patent. , (2003).</li><li>. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=.">.</a> Ochrana proti korozi. Inhibitory koroze kov&#367; a slitin v neutr&#225;ln&#237;ch vodn&#237;ch prost&#345;ed&#237;ch. Laboratorn&#237; metody stanoven&#237; ochrann&#233; &#250;&#269;innosti (in Czech). , (1990).</li><li>Mat&#283;jovsk&#253;, L., Baro&#353;, P., Posp&#237;&#353;il, M., Mac&#225;k, J., Straka, P., Maxa, D. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Testov&#225;n&#237;+korozn&#237;ch+vlastnost&#237;+lihobenz&#237;nov&#253;ch+sm&#283;s&#237;+na+oceli,+hlin&#237;ku+m&#283;di+a+mosazi+(Testing+of+Corrosion+Properties+of+Ethanol-Gasoline+Blends+on+Steel,+Aluminum,+Copper+and+Brass)+(in+Czech).">Testov&#225;n&#237; korozn&#237;ch vlastnost&#237; lihobenz&#237;nov&#253;ch sm&#283;s&#237; na oceli, hlin&#237;ku m&#283;di a mosazi (Testing of Corrosion Properties of Ethanol-Gasoline Blends on Steel, Aluminum, Copper and Brass) (in Czech).</a> Paliva. 5 (2), 54-62 (2013).</li><li>Cempirkova, D., Hadas, R., Mat&#283;jovsk&#253;, L., Sauerstein, R., Ruh, M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Impact+of+E100+Fuel+on+Bearing+Materials+Selection+and+Lubricating+Oil+Properties.">Impact of E100 Fuel on Bearing Materials Selection and Lubricating Oil Properties.</a> SAE Technical Paper. , (2016).</li><li>Yoo, Y., Park, I., Kim, J., Kwak, D., Ji, W. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Corrosion+characteristics+of+aluminum+alloy+in+bio-ethanol+blended+gasoline+fuel:+Part+1.+The+corrosion+properties+of+aluminum+alloy+in+high+temperature+fuels.">Corrosion characteristics of aluminum alloy in bio-ethanol blended gasoline fuel: Part 1. The corrosion properties of aluminum alloy in high temperature fuels.</a> Fuel. 90 (3), 1208-1214 (2011).</li><li>Bhola, S. M., Bhola, R., Jain, L., Mishra, B., Olson, D. L. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Corrosion+behavior+of+mild+carbon+steel+in+ethanolic+solutions.">Corrosion behavior of mild carbon steel in ethanolic solutions.</a> Journal of Materials Engineering and Performance. 20 (3), 409-416 (2011).</li><li>Jafari, H., Idris, M. H., Ourdjini, A., Rahimi, H., Ghobadian, B. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=EIS+study+of+corrosion+behavior+of+metallic+materials+in+ethanol+blended+gasoline+containing+water+as+a+contaminant.">EIS study of corrosion behavior of metallic materials in ethanol blended gasoline containing water as a contaminant.</a> Fuel. 90 (3), 1181-1187 (2011).</li><li>Traldi, S., Costa, I., Rossi, J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Corrosion+of+spray+formed+Al-Si-Cu+alloys+in+ethanol+automobile+fuel.">Corrosion of spray formed Al-Si-Cu alloys in ethanol automobile fuel.</a> Key Engineering Materials. , 352-357 (2001).</li><li>Nie, X., Li, X., Northwood, D. O. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Corrosion+Behavior+of+metallic+materials+in+ethanol-gasoline+alternative+fuels.">Corrosion Behavior of metallic materials in ethanol-gasoline alternative fuels.</a> Material Science Forum. 546, 1093-1100 (2007).</li><li>Sridhar, N., Price, K., Buckingham, J., Dante, J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Stress+corrosion+cracking+of+carbon+steel+in+ethanol.">Stress corrosion cracking of carbon steel in ethanol.</a> Corrosion. 62 (8), 687-702 (2006).</li><li>Mate&#780;jovsky&#769;, L., Mac&#225;k, J., Pospi&#769;s&#780;il, M., Baros&#780;, P., Stas&#780;, M., Krausova&#769;, A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Study+of+Corrosion+of+Metallic+Materials+in+Ethanol-Gasoline+Blends:+Application+of+Electrochemical+Methods.">Study of Corrosion of Metallic Materials in Ethanol-Gasoline Blends: Application of Electrochemical Methods.</a> Energy &amp; Fuels. 31 (10), 10880-10889 (2017).</li><li>Mat&#283;jovsk&#253;, L., Mac&#225;k, J., Posp&#237;&#353;il, M., Sta&#353;, M., Baro&#353;, P., Krausov&#225;, A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Study+of+Corrosion+Effects+of+Oxidized+Ethanol-Gasoline+Blends+on+Metallic+Materials.">Study of Corrosion Effects of Oxidized Ethanol-Gasoline Blends on Metallic Materials.</a> Energy Fuels. 32 (4), 5145-5156 (2018).</li></ol>

The authors have nothing to disclose.

The basic principle of the dynamic test and both static tests is the evaluation of weight losses of metallic samples in metal-corrosion environment (fuel) systems depending on time until steady state is achieved (i.e., no further weight loss occurs). The corrosion rate of the metal in the corrosion environment is calculated from the weight loss and time. The advantage of the long-term static corrosion test (Step 1) is the reliability of the obtained results, the simplicity and l...

Corrosion causes great material and economic damage around the world. It causes considerable material losses due to partial or complete material disintegration. The released particles can be understood as impurities; they can negatively change the composition of the surrounding environment or the functionality of various devices. Also, corrosion can cause negative visual changes of materials. Thus, there is a need to understand corrosion processes in more detail to develop measures to prevent corrosion and minimize its potential risks1.
Considering environmental issues and the limited fossil fuel reserves, there is an increasing interest in alternative fuels, among which biofuels from renewable sources play an important role. There are a number of different potentially available biofuels, but bioethanol produced from biomass currently is the most suitable alternative for substituting (or blending with) gasolines. The use of bioethanol is regulated by the Directive 2009/28/EC in the European Union2,3.
Ethanol (bioethanol) has substantially different properties in comparison with gasolines. It is highly polar, conductive, completely miscible with water, etc. These properties make ethanol (and fuel blends containing ethanol also) aggressive in terms of corrosion4. For fuels with low ethanol content, contamination by small amounts of water can cause separation of the water-ethanol phase from the hydrocarbon phase and this can be highly corrosive. Anhydrous ethanol itself can be aggressive for some less noble metals and cause &#34;dry corrosion&#34;5. With existing cars, corrosion can occur in some metallic parts (especially from copper, brass, aluminum or carbon steel) that come into contact with the fuel. Furthermore, polar contaminants (especially chlorides) may contribute to the corrosion as a source of contamination; oxygen solubility and oxidation reactions (that can occur in ethanol-gasoline blends (EGBs) and be a source of acidic substances) can also play an important role6,7.
One of the possibilities on how to protect metals from corrosion is the use of so-called corrosion inhibitors that make it possible to substantially slow down (inhibit) corrosion processes8. The selection of corrosion inhibitors depends on the type of corrosive environment, the presence of corrosion stimulators, and particularly on the mechanism of a given inhibitor. Currently, there is no versatile database or classification available that would enable simple orientation in corrosion inhibitors.
Corrosion environments can be divided into aqueous or non-aqueous, as the intensity and the nature of corrosion processes in these environments differ significantly. For non-aqueous environments, electrochemical corrosion connected with different chemical reactions is typical, whereas only electrochemical corrosion (without other chemical reactions) occurs in aqueous environments. Moreover, electrochemical corrosion is much more intensive in aqueous environments9.
In non-aqueous, liquid organic environments, corrosion processes depend on the degree of polarity of the organic compounds. This is associated with the substitution of hydrogen in some functional groups by metals, which is connected with the change of the characteristics of the corrosion processes from electrochemical to chemical, for which lower corrosion rates are typical in comparison with electrochemical processes. Non-aqueous environments typically have low values of electrical conductivity9. To increase conductivity in organic environments, it is possible to add so called supporting electrolytes such as tetraalkylammonium tetrafluoroborates or perchlorates. Unfortunately, these substances can have inhibitive properties, or, on the contrary, increase corrosion rates10.
There are several methods for short-term and long-term testing of corrosion rates of metallic materials or the efficiency of corrosion inhibitors, namely with or without environment circulation, i.e., static and dynamic corrosion test, respectively11,12,13,14,15. For both methods, the calculation of the corrosion rates of metallic materials is based on weight losses of the tested materials over a certain time period. Recently, electrochemical methods are becoming more important in corrosion studies due to their high efficiency and short measurement times. Moreover, they can often provide more information and a more comprehensive view on corrosion processes. The most commonly used methods are electrochemical impedance spectroscopy (EIS), potentiodynamic polarization and the measurement of the stabilization of the corrosion potential in time (in a planar, two-electrode or in a three electrode arrangement)16,17,18,19,20,21,22,23.
Here, we present five methods for the short-term and long-term testing of the corrosion aggressiveness of an environment, the corrosion resistance of metallic materials and the efficiency of corrosion inhibitors. All of the methods are optimized for measurements in non-aqueous environments and are demonstrated on EGBs. The methods allow for obtaining representative and reproducible results, which can help to understand corrosion processes in more detail to prevent and minimize corrosion damages.
For the static immersion corrosion test in metal-liquid systems, static corrosion tests in metal-liquid systems can be performed in a simple apparatus consisting of a 250 mL bottle equipped with a hook for hanging an analyzed sample, see Figure 1.
For the dynamic corrosion test with liquid circulation, metal corrosion inhibitors or the aggressiveness of liquids (fuels) can be tested in a flow apparatus with the circulation of the liquid medium presented in Figure 2. The flow apparatus consists of a tempered part and a reservoir of the tested liquid. In the tempered part, the tested liquid is in contact with a metallic sample in the presence of air oxygen or in an inert atmosphere. The gas (air) supply is ensured by a frit with the tube reaching the bottom of the flask. The reservoir of the tested liquid containing about 400-500 mL of the tested liquid is connected with a reflux cooler that allows for the connection of the apparatus with the atmosphere. In the cooler, the evaporated portion of the liquid is frozen at -40 &#176;C. The peristaltic pump allows for the pumping of the liquid at a suitable rate of about 0.5 Lh-1 via a closed circuit from chemically stable and inert materials (e.g., Teflon, Viton, Tygon) from the storage part into the tempered part, from which the liquid returns via the overflow into the storage part.
For the static immersion corrosion test with a reflux cooler in the presence of gaseous medium, corrosion inhibitors, the resistance of metallic materials or the aggressiveness of a liquid environment can be tested in the apparatus presented in Figure 3. The apparatus contains two parts. The first part consists of a two-necked, tempered 500 mL flask with a thermometer. The flask contains a sufficient amount of a liquid environment. The second part consists of (i) a reflux cooler with a ground glass joint to achieve a tight connection with the flask, (ii) a hanger for placing the metallic samples and (iii) a frit with a tube for gas (air) supply reaching the bottom of the flask. The apparatus is connected to the atmosphere via the cooler that avoids liquid evaporation.
The apparatus for the electrochemical measurements in the two-electrode arrangement is presented in Figure 4. The electrodes are made from metal sheets (3 x 4 cm, from mild steel), which are completely embedded in epoxide resin on one side to protect them from the surrounding corrosive environment. Both electrodes are screwed to the matrix so that the distance between them is about 1 mm22.
The electrochemical measurements in the three-electrode arrangement consist of working, reference and auxiliary electrodes placed in the measuring cell so that a small distance between the electrodes is ensured; see Figure 5. As the reference electrode, calomel or argent-chloride electrodes with a salt bridge containing either (i) a 3 molL-1solution of potassium nitrate (KNO3) or (ii) a 1 molL-1solution of lithium chloride (LiCl) in ethanol can be used. A platinum wire, mesh or plate can be used as the auxiliary electrode. The working electrode consists of (i) a measuring part (tested material with a screw thread) and (ii) a screw attachment isolated from the corrosion environment, see Figure 6. The electrode must be sufficiently isolated by an anti-underflow seal.

<table><tbody><tr><td>sulfuric acid</td><td>Penta s.r.o., Czech Republic</td><td>20450-11000</td><td>p.a. 96 %&lt;br/&gt; &lt;strong&gt;CAS:&lt;/strong&gt; 7664-93-9&lt;br/&gt; http://www.pentachemicals.eu/</td></tr><tr><td>acetic acid</td><td>Penta s.r.o., Czech Republic</td><td>20000-11000</td><td>p.a. 99 %&lt;br/&gt; &lt;strong&gt;CAS:&lt;/strong&gt; 64-19-7&lt;br/&gt; http://www.pentachemicals.eu/</td></tr><tr><td>sodium sulphate anhydrous</td><td>Penta s.r.o., Czech Republic</td><td>25770-31000</td><td>p.a. 99,9 %&lt;br/&gt; &lt;strong&gt;CAS:&lt;/strong&gt; 7757-82-6&lt;br/&gt; http://www.pentachemicals.eu/</td></tr><tr><td>sodium chlorate</td><td>Penta s.r.o., Czech Republic</td><td></td><td>p.a. 99,9 %&lt;br/&gt; &lt;strong&gt;CAS:&lt;/strong&gt;&amp;nbsp;7681-52-9&lt;br/&gt; http://www.pentachemicals.eu/</td></tr><tr><td>demineralized water</td><td>-</td><td></td><td></td></tr><tr><td>ethanol</td><td>Penta s.r.o., Czech Republic</td><td>71250-11000</td><td>p.a. 99 %&amp;nbsp;&lt;br/&gt; &lt;strong&gt;CAS:&lt;/strong&gt; 64-17-5&lt;br/&gt; http://www.pentachemicals.eu/</td></tr><tr><td>gasoline fractions</td><td>Cesk&amp;aacute; rafinersk&amp;aacute; a.s., Kralupy nad Vltavou, Czech Republic</td><td></td><td>in compliance with EN 228 (57.4 vol. % of saturated hydrocarbons, 13.9 vol. % of olefins, 28.7 vol. % of aromatic hydrocarbons, and 1 mg/kg of sulfur)</td></tr><tr><td>Aceton</td><td>Penta s.r.o., Czech Republic</td><td></td><td>pure 99 %</td></tr><tr><td>Toluen</td><td>Penta s.r.o., Czech Republic</td><td></td><td>pure 99 %</td></tr><tr><td>&lt;strong&gt;Name&lt;/strong&gt;</td><td>&lt;strong&gt;Company&lt;/strong&gt;</td><td>&lt;strong&gt;Catalog Number&lt;/strong&gt;</td><td>&lt;strong&gt;Comments&lt;/strong&gt;</td></tr><tr><td>&lt;strong&gt;Potenciostat/Galvanostat/ZRA&lt;/strong&gt;</td><td></td><td></td><td></td></tr><tr><td>Reference 600</td><td>Gamry Instruments, USA</td><td></td><td>https://www.gamry.com/</td></tr><tr><td>1250 Frequency Response Analyser</td><td>Solarthrone</td><td></td><td></td></tr><tr><td>SI 1287 Elecrtochemical Interference</td><td>Solarthrone</td><td></td><td></td></tr><tr><td>&lt;strong&gt;Name&lt;/strong&gt;</td><td>&lt;strong&gt;Company&lt;/strong&gt;</td><td>&lt;strong&gt;Catalog Number&lt;/strong&gt;</td><td>&lt;strong&gt;Comments&lt;/strong&gt;</td></tr><tr><td>&lt;strong&gt;Software&lt;/strong&gt;</td><td></td><td></td><td></td></tr><tr><td>Framework 5.68</td><td>Gamry Instruments, USA</td><td></td><td>https://www.gamry.com/</td></tr><tr><td>Echem Analyst 5.68</td><td>Gamry Instruments, USA</td><td></td><td>https://www.gamry.com/</td></tr><tr><td>Corrware 2.5b</td><td>Scribner</td><td></td><td>http://www.scribner.com/</td></tr><tr><td>CView 2.5b</td><td>Scribner</td><td></td><td>http://www.scribner.com/</td></tr><tr><td>Zview 3.2c</td><td>Scribner</td><td></td><td>http://www.scribner.com/</td></tr><tr><td>MS Excel 365</td><td>Microsoft</td><td></td><td></td></tr><tr><td>&lt;strong&gt;Name&lt;/strong&gt;</td><td>&lt;strong&gt;Company&lt;/strong&gt;</td><td>&lt;strong&gt;Catalog Number&lt;/strong&gt;</td><td>&lt;strong&gt;Comments&lt;/strong&gt;</td></tr><tr><td>&lt;strong&gt;Grinder&lt;/strong&gt;</td><td></td><td></td><td></td></tr><tr><td>Kompak 1031</td><td>MTH (Materials Testing Hrazdil)</td><td></td><td></td></tr></tbody></table>

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 above mentioned methods were used to measure the corrosion data of mild steel (consisting of 0.16 wt. % of C, 0.032 wt. % of P, 0.028 wt. % of S and balance F)22 in the environment of ethanol-gasoline blends (EGBs) containing 10 and 85 vol. % of ethanol (E10 and E85), respectively. For the preparation of these EGBs, gasoline in compliance with the requirements of the EN 228 containing 57.4 vol. % of saturated hydrocarbons, 13.9 vol. % of olefins, 28.7 vol. % of...

Watch this Scientific Journal Video about Metal Corrosion and the Efficiency of Corrosion Inhibitors in Less Conductive Media at JoVE.com

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

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, ...

metal-corrosion-efficiency-corrosion-inhibitors-less-conductive

Research

Education

JoVE Journal

JoVE Core

Chemistry

Environment

Electrochemistry

SCIENTISTS IN ACTION

17.8K Views.  University of Chemistry and Technology Prague. 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.

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

Determination of Microbial Extracellular Enzyme Activity in Waters, Soils, and Sediments using High Throughput Microplate Assays

Much of the nutrient cycling and carbon processing in natural environments occurs through the activity of extracellular enzymes released by microorganisms. Thus, measurement of the activity of these extracellular enzymes can give insights into the rates of ecosystem level processes, such as organic matter decomposition or nitrogen and phosphorus mineralization. Assays of extracellular enzyme activity in environmental samples typically involve exposing the samples to artificial colorimetric or fluorometric substrates and tracking the rate of substrate hydrolysis. Here we describe microplate based methods for these procedures that allow the analysis of large numbers of samples within a short time frame. Samples are allowed to react with artificial substrates within 96-well microplates or deep well microplate blocks, and enzyme activity is subsequently determined by absorption or fluorescence of the resulting end product using a typical microplate reader or fluorometer. Such high throughput procedures not only facilitate comparisons between spatially separate sites or ecosystems, but also substantially reduce the cost of such assays by reducing overall reagent volumes needed per sample.

Microplate based procedures are described for the colorimetric or fluorometric analysis of extracellular enzyme activity. These procedures allow for the rapid assay of such activity in large numbers of environmental samples within a manageable time frame.

Much of the nutrient cycling and carbon  processing in natural environments occurs through the activity of extracellular  enzymes released by ...

Clean Sampling and Analysis of River and Estuarine Waters for Trace Metal Studies

Most of the trace metal concentrations in ambient waters obtained a few decades ago have been considered unreliable owing to the lack of contamination control. Developments of some techniques aiming to reduce trace metal contamination in the last couple of decades have resulted in concentrations reported now being orders of magnitude lower than those in the past. These low concentrations often necessitate preconcentration of water samples prior to instrumental analysis of samples. Since contamination can appear in all phases of trace metal analyses, including sample collection (and during preparation of sampling containers), storage and handling, pretreatments, and instrumental analysis, specific care needs to be taken in order to reduce contamination levels at all steps. The effort to develop and utilize "clean techniques" in trace metal studies allows scientists to investigate trace metal distributions and chemical and biological behavior in greater details. This advancement also provides the required accuracy and precision of trace metal data allowing for environmental conditions to be related to trace metal concentrations in aquatic environments.
This protocol that is presented here details needed materials for sample preparation, sample collection, sample pretreatment including preconcentration, and instrumental analysis. By reducing contamination throughout all phases mentioned above for trace metal analysis, much lower detection limits and thus accuracy can be achieved. The effectiveness of "clean techniques" is further demonstrated using low field blanks and good recoveries for standard reference material. The data quality that can be obtained thus enables the assessment of trace metal distributions and their relationships to environmental parameters.

Special care using "clean techniques" is required to properly collect and process water samples for trace metal studies in aquatic environments. A protocol for sampling, processing, and analytical procedures with the aim of obtaining reliable environmental monitoring data and results with high sensitivity for detailed trace metal studies is presented.

Most of the trace metal concentrations in ambient waters obtained a few decades ago have been considered unreliable owing to the lack of contamination ...

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.

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 ...

The Evolution of Silica Nanoparticle-polyester Coatings on Surfaces Exposed to Sunlight

Corrosion of metallic surfaces is prevalent in the environment and is of great concern in many areas, including the military, transport, aviation, building and food industries, amongst others. Polyester and coatings containing both polyester and silica nanoparticles (SiO2NPs) have been widely used to protect steel substrata from corrosion. In this study, we utilized X-ray photoelectron spectroscopy, attenuated total reflection infrared micro-spectroscopy, water contact angle measurements, optical profiling and atomic force microscopy to provide an insight into how exposure to sunlight can cause changes in the micro- and nanoscale integrity of the coatings. No significant change in surface micro-topography was detected using optical profilometry, however, statistically significant nanoscale changes to the surface were detected using atomic force microscopy. Analysis of the X-ray photoelectron spectroscopy and attenuated total reflection infrared micro-spectroscopy data revealed that degradation of the ester groups had occurred through exposure to ultraviolet light to form COO&#903;, -H2C&#903;, -O&#903;, -CO&#903; radicals. During the degradation process, CO and CO2 were also produced.

Two types of surfaces, polyester-coated steel and polyester coated with a layer of silica nanoparticles, were studied. Both surfaces were exposed to sunlight, which was found to cause substantial changes in the chemistry and nanoscale topography of the surface.

Corrosion of metallic surfaces is prevalent in the environment and is of great concern in many areas, including the military, transport, aviation, ...

Engineering

Determining the Chemical Composition of Corrosion Inhibitor/Metal Interfaces with XPS: Minimizing Post Immersion Oxidation

An approach for acquiring more reliable X-ray photoelectron spectroscopy data from corrosion inhibitor/metal interfaces is described. More specifically, the focus is on metallic substrates immersed in acidic solutions containing organic corrosion inhibitors, as these systems can be particularly sensitive to oxidation following removal from solution. To minimize the likelihood of such degradation, samples are removed from solution within a glove box purged with inert gas, either N2 or Ar. The glove box is directly attached to the load-lock of the ultra-high vacuum X-ray photoelectron spectroscopy instrument, avoiding any exposure to the ambient laboratory atmosphere, and thus reducing the possibility of post immersion substrate oxidation. On this basis, one can be more certain that the X-ray photoelectron spectroscopy features observed are likely to be representative of the in situ submerged scenario, e.g. the oxidation state of the metal is not modified.

A protocol to avoid the oxidation of metallic substrates during sample transfer from an inhibited acidic solution to an X-ray photoelectron spectrometer is presented.

An approach for acquiring more reliable X-ray photoelectron spectroscopy data from corrosion inhibitor/metal interfaces is described. More specifically, ...

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 ...

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, ...

Imaging Corrosion at the Metal-Paint Interface Using Time-of-Flight Secondary Ion Mass Spectrometry

Corrosion developed at the paint and aluminum (Al) metal-paint interface of an aluminum alloy is analyzed using time-of-flight secondary ion mass spectrometry (ToF-SIMS), illustrating that SIMS is a suitable technique to study the chemical distribution at a metal-paint interface. The painted Al alloy coupons are immersed in a salt solution or exposed to air only. SIMS provides chemical mapping and 2D molecular imaging of the interface, allowing direct visualization of the morphology of the corrosion products formed at the metal-paint interface and mapping of the chemical after corrosion occurs. The experimental procedure of this method is presented to provide technical details to facilitate similar research and highlight pitfalls that may be encountered during such experiments.

Time-of-flight secondary ion mass spectrometry is applied to demonstrate the chemical mapping and corrosion morphology at the metal-paint interface of an aluminum alloy after being exposed to a salt solution compared with a specimen exposed to air.

Corrosion developed at the paint and aluminum (Al) metal-paint interface of an aluminum alloy is analyzed using time-of-flight secondary ion mass ...

Co-localizing Kelvin Probe Force Microscopy with Other Microscopies and Spectroscopies: Selected Applications in Corrosion Characterization of Alloys

Kelvin probe force microscopy (KPFM), sometimes referred to as surface potential microscopy, is the nanoscale version of the venerable scanning Kelvin probe, both of which measure the Volta potential difference (VPD) between an oscillating probe tip and a sample surface by applying a nulling voltage equal in magnitude but opposite in sign to the tip-sample potential difference. By scanning a conductive KPFM probe over a sample surface, nanoscale variations in surface topography and potential can be mapped, identifying likely anodic and cathodic regions, as well as quantifying the inherent material driving force for galvanic corrosion.
Subsequent co-localization of KPFM Volta potential maps with advanced scanning electron microscopy (SEM) techniques, including back scattered electron (BSE) images, energy dispersive spectroscopy (EDS) elemental composition maps, and electron backscattered diffraction (EBSD) inverse pole figures can provide further insight into structure-property-performance relationships. Here, the results of several studies co-localizing KPFM with SEM on a wide variety of alloys of technological interest are presented, demonstrating the utility of combining these techniques at the nanoscale to elucidate corrosion initiation and propagation.
Important points to consider and potential pitfalls to avoid in such investigations are also highlighted: in particular, probe calibration and the potential confounding effects on the measured VPDs of the testing environment and sample surface, including ambient humidity (i.e., adsorbed water), surface reactions/oxidation, and polishing debris or other contaminants. Additionally, an example is provided of co-localizing a third technique, scanning confocal Raman microscopy, to demonstrate the general applicability and utility of the co-localization method to provide further structural insight beyond that afforded by electron microscopy-based techniques.

Kelvin probe force microscopy (KPFM) measures surface topography and differences in surface potential, while scanning electron microscopy (SEM) and associated spectroscopies can elucidate surface morphology, composition, crystallinity, and crystallographic orientation. Accordingly, the co-localization of SEM with KPFM can provide insight into the effects of nanoscale composition and surface structure on corrosion.

Kelvin probe force microscopy (KPFM), sometimes referred to as surface potential microscopy, is the nanoscale version of the venerable scanning Kelvin ...

Corrosion

The degradation of metals due to natural electrochemical processes is known as corrosion. Rust formation on iron, tarnishing of silver, and the blue-green patina that develops on copper are examples of corrosion. Corrosion involves the oxidation of metals. Sometimes it is protective, such as the oxidation of copper or aluminum, wherein a protective layer of metal oxide or its derivatives forms on the surface, protecting the underlying metal from further oxidation. In other cases, corrosion is damaging to the metal, such as the rusting of iron.
Undesirable Redox Reaction: The Rusting of Iron
Rusting occurs due to exposure of iron to oxygen and water. Rust formation involves the creation of a galvanic cell at the surface of iron, which results in the generation of iron(II). The relevant redox reactions that occur at the anodic (oxidation of iron) and cathodic (reduction of oxygen) regions formed on the iron surface include:
<img alt="Eq1" src="/files/ftp_upload/11440/11440_Equation_1.png" style="text-align: center; height: 150px;" />
The iron(II) further reacts with humid air, forming an iron(III) oxide hydrate, commonly known as rust.
<img alt="Eq2" src="/files/ftp_upload/11440/11440_Equation_2.png" style="text-align: center; height: 50px;" />
The hydrate&#39;s stoichiometry varies with the amount of water to which iron(II) is exposed, as indicated by the use of x in the compound formula. Moisture, the presence of acids and electrolytes increases the rate of formation of rust. Unlike the patina on copper, the formation of rust does not create a protective layer, and so corrosion of the iron continues as the rust flakes off and exposes fresh iron to the atmosphere.
Prevention of Corrosion
Various methods can be used to prevent corrosion. One way is to keep the metal surface painted to avoid contact with water and oxygen. Alloying of metals, like mixing iron with small amounts of chromium in stainless steel, is another effective method to prevent corrosion. The chromium collects near the surface and undergoes oxidation, thus, effectively protecting the iron from corrosion.
Iron and other metals may also be protected from corrosion by galvanization, a process in which the metal to be protected is coated with a layer of a more readily oxidized metal, usually zinc. When the zinc layer is intact, it prevents air from contacting the underlying iron and thus prevents corrosion. If the zinc layer is breached by either corrosion or mechanical abrasion, the iron may still be protected from corrosion by a cathodic protection process, which is described in the next paragraph.
Cathodic protection utilizes the principle of converting the metal to be protected into a cathode in an electrochemical reaction. This is achieved by connecting the protected metal to a more active or easily oxidized metal such as zinc or magnesium, known as the sacrificial anode. The anode corrodes and gets used up protecting the metal that serves as the cathode. Cathodic protection is most commonly used in household appliances such as water heaters and underground water storage tanks. Importantly, cathodic protection can be used for metals other than just iron.
This text is adapted from <a href="https://openstax.org/books/chemistry-2e/pages/17-6-corrosion">OpenStax, Chemistry 2e, Chapter 17.6: Corrosion</a>.

Corrosion: Rodox Reaction in Rusting of Iron; Prevention

The degradation of metals due to natural electrochemical processes is known as corrosion. Rust formation on iron, tarnishing of silver, and the blue-green ...