Name: metal corrosion and the efficiency of corrosion inhibitors in less conductive media
Uploaded: 2018-11-03T13:00:00
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 ...

<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 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 % 
			CAS: 7664-93-9 
			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 % 
			CAS: 64-19-7 
			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 % 
			CAS: 7757-82-6 
			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 % 
			CAS:&#160;7681-52-9 
			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 %&#160; 
			CAS: 64-17-5 
			http://www.pentachemicals.eu/</td>
		</tr>
		<tr>
			<td>gasoline fractions</td>
			<td>Cesk&#225; rafinersk&#225; 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>Name</td>
			<td>Company</td>
			<td>Catalog Number</td>
			<td>Comments</td>
		</tr>
		<tr>
			<td>Potenciostat/Galvanostat/ZRA</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>Name</td>
			<td>Company</td>
			<td>Catalog Number</td>
			<td>Comments</td>
		</tr>
		<tr>
			<td>Software</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>Name</td>
			<td>Company</td>
			<td>Catalog Number</td>
			<td>Comments</td>
		</tr>
		<tr>
			<td>Grinder</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, ...

These methods can help answer the questions about the corrosion resistance of metallic materials, the corrosion aggressiveness of different environments, and the efficiency of corrosion inhibitors in different environments. The main advantage of these methods is that they can be applied in both aqueous and non-aqueous environments. This method can be useful in the automotive and fuel industry for study of the corrosion effect of ethanol gasoline blends on different construction materials within fuel systems.Demonstrating the procedure will be Lukas Matejovsky, a member of my team. To test the static immersion corrosion of metal liquid systems, begin by adding 100 to 150 milliliters of the tested liquid corrosion environment to a 250-milliliter bottle equipped with a hook for hanging an analyzed sample, and use 1, 200-mesh sandpaper to grind and polish the surface of the metallic sample under running water to achieve an even adjustment of the surfaces. Next, thoroughly degrease the sample surface with about 25 milliliters of acetone and about 25 milliliters of ethanol.After drying, weigh the sample on an analytical balance to an accuracy of four decimal places, and hang the metallic sample within the bottle so that the sample is emerged within the liquid, but does not lie on the bottom of the bottle. Then, close the bottle tightly enough to prevent liquid evaporation and air entry. Remove the metallic sample from the bottle at regular intervals for rinsing with about 25 milliliters of acetone, using pulp tissue to remove any excess corrosion products from the surface.Then weigh the sample to four decimal places, and return the sample to the bottle. When equilibrium is achieved within the metal liquid system, terminate the experiment. For a dynamic corrosion test, add 500 milliliters of the tested liquid corrosion environment into the four-necked flask of the storage part of the apparatus, and lubricate the ground glass joints of the flask with a silicone grease.Fix a reflux cooler, thermometer, suction capillary connected to a pump, and the overflow connected to the tempered part, on the necks of the flask. And set the cryostat connected to the cooler to 40 degrees Celsius. Fill the closed cooling circuit with ethanol.Using the capillary for the fuel pumping, connect the pump to the preheating spiral of the tempered part of the flask that brings preheated fuel via the bottom of the measuring cell. Set the desired pump fuel flow rate to 500 milliliters per hour, and the thermostat for the tempered part of the flask to 40 degrees Celsius. Once the tempered part of the flask is filled with fuel, and the fuel starts to flow via the overhead 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 on the hanger.Use a pressure vessel to connect the frit to the tube for the air supply via a pressure regulator and a flow meter, and set the desired gas flow rate on the flow meter to 20 to 30 milliliters per minute. Then, remove the metallic sample from the tempered part of the flask and rinse, polish and weigh the sample to determine the sample's surface loss over time, as just demonstrated. For a static immersion corrosion test, add 200 to 300 milliliters of the liquid test sample into the tempered flask, and hang a ground, polished, degreased and weighed metal sample on the hook of the reflux cooler.Lubricate the ground glass joint to the cooler with the silicone grease, and fix the cooler into the flask. Connect the frit to the tube for the air supply with a pressure vessel via a pressure regulator and a flow meter, and set the desired gas flow rate to 80 milliliters per minute on the flow meter. Then, set the temperature to 80 degrees Celsius on the thermostat for flask tempering, and do 40 degrees Celsius on the cryostat connected to the cooler.After the appropriate experimental exposure period, remove the metallic sample from the apparatus, and rinse, polish and weigh the sample to determine the sample's surface loss over the time, as just demonstrated. For electrochemical measurements in a two-electrode arrangement, first, remove the electrode system from the measuring cell, and unscrew the system. Adjust the surface of the electrodes, as just demonstrated, and reassemble the electrode system.Fill the measuring cell with 80 milliliters of the tested liquid corrosion environment, and close the measuring cell through the electrode system. Place the whole cell into a grounded Faraday cage and connect the galvanostat and potentiostat to the electrode system, so that one electrode of the system acts as a reference electrode, and the other electrode acts as a working, and an auxiliary, electrode, at the same time. In the measurement software, set the sequence containing the open circuit potential measurements and the electrochemical impedance spectroscopy measurement, and perform the stabilization for at least 30 minutes to minimize the potential change.Then, acquire the electrochemical impedance spectroscopy measurement at a sufficiently high amplitude, according to the conductivity of the corrosion environment, and at a sufficient range of frequencies to allow evaluation of the low and high-frequency parts of the spectra. For electrochemical measurements in a three-electrode arrangement, adjust the measuring part of the working electrode from the tested metallic material, as demonstrated, and screw the part onto the electrode extension. Fill the measurement cell with 100 milliliters of the tested liquid corrosion environment, and close the cell with a cap, through which the working electrode from the tested material, and the auxiliary electrode from the platinum wire, are led.Make sure that the auxiliary electrode is twisted around the working electrode. Insert the reference electrode with a bridge through the side entry of the cell, so that the reference electrode is as close to the working electrode as possible, without the electrodes touching each other. 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.Then, in the software of the measuring devices used, set the measuring sequence, containing the measurement of the open circuit potential, for at least 20 minutes, the electrochemical impedance spectroscopy in the range of about one megahertz to one millihertz, and an amplitude value of five to 20 millivolts, and the polarization characteristics between 200 to 500 millivolts to the corrosion potential. In a static corrosion test, 1, 200 hours are sufficient to achieve stabilization of the mild steel E10 and E85 fuel systems, while 340 hours are required for stabilization within the dynamic corrosion system. The efficiency of the corrosion inhibitor is also evident in both of the fuels, as substantially lower material losses are observed when the inhibitor is applied.The removal of the surface corrosion products by pickling enables the acquisition of real material losses that are important for calculation of the efficiency of the corrosion inhibitors. When the conductivity of an environment is low, the spectrum consists of only one high-frequency half circle, making it possible to evaluate the properties that characterize the used environment only. When the conductivity of an environment is high enough, the spectrum consists of both high and low-frequency regions that form two, relatively well-separated, half circles.Here, the Tafel curves of mild steel in the environment of the aggressive E85 fuel without the inhibitor before, and after, the potential loss drop compensation, as well as in the presence of an amine-based inhibitor, are shown. While attempting these methods it's important to remember to minimize the Wang error and to carefully perform the adjustment of the sample surface. For the static and dynamic tests, the corrosion resistance of the metallic materials, or the corrosion aggressiveness of the different environments, can be evaluated based on the corrosion rate of the tested materials during the testing.For the electrochemical methods, the corrosion resistance of the metallic materials, or the corrosion aggressiveness of the different environments, can be evaluated based on the polarization correctory sticks. All of the presented methods enable us to test the efficiency of corrosion inhibitors.

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