The Study of Composition Corrosion Cells - Lab Report Example

The Study of Composition Corrosion Cells: Experiment 3 Department: Module no.: Title: Lecturer: Student’s name: Student ID: Date: Table of contents 1. Abstract…………………………………………………………………………….…….…..3 2. Introduction…………………………………..…………………………………….…….......4 3. Objectives ………………………………………………………………………….…….......5 4. Hypothesis…………………………………..……………………………...…..….……........5 a. Null hypothesis…………………………………..………………………………..…….....5 b. Alternative hypothesis…………………………………..……………………..…..……....5 5. Methods and materials…………………………………..……….…………….………..........6 6. Results…………………………………..…………………………………….…...…..……...7 7. Discussion…………………………………..…………………..…………….……………...10 8. Conclusion…………………………………..……………………..………….………...........11 9. Recommendations…………………………………..……………………..…..………...........11 10. References and Bibliography …………………………………..…………….………............13 1. Abstract Dissimilar metal corrosion is kind of corrosion that occurs when there is a relationship between dissimilar metals. When the different metals are connected through an electrolyte, electric current flows through the dissimilar metals causing a potential variation to occur, this leads to corrosion. This type corrosion is also known as galvanic corrosion or bimetallic corrosion. This type of corrosion occurs at the junctions of the metals or regions of construction where metal encounters another. For these reactions to occur there must be media in which the reactions occur. Some media in which these electrochemical reactions occur include water, acidic and basic electrolytes. With these media present, the reactions are fast and corrosion occurs as these reactions take place. This report emphasizes on the causes, management and cases that involve the galvanic corrosion. 2. Introduction The process in which a metal reacts by chemical reaction with the surrounding materials to form an oxide or other combination is corrosion. This process leads to progressive destruction of the face of the metal. Corrosion can also occur when two dissimilar metals have an electrical connection, with one end inside an electrolyte. In this case, an electric current is produced and corrosion can be fast and again especially if there is the presence of impurities. This form of the cell is known as the COMPOSITION CELL or GALVANIC CELL. The following reasons must exist for the cell to be vulnerable to corrosion: - 1) Two different metals must be in electrical contact, that is, there is an electrical connection between the electrodes. 2) A complete electrical circuit 3) The metals in question must be different Two half-cell reactions are involved for an electrochemical to occur, they include oxidation and reduction. This experiment looks at the metal arrangement according to level of corrosion for different electrochemical potential difference in these cells. To a more extend, it also discusses the key to solve the problem brought about by corrosion. For example, iron corroding in water which has PH which is almost light has the following reactions Cathode reaction:  And Anode reaction:  Different metal alloys have different anodic and cathodic reactions when exposed to different environments. A voltmeter is a voltage instrument for measuring potential difference in cells. Thus, terminals give a numerical standard electrode potential as can be seen in the table below. Table 1: Table of Electrochemical series for independent metals In this case, the previous studies have shown that as the potential of metal becomes more negative, so does the metal become more vulnerable to corrosion. When dissimilar metals are placed in an electrolyte, they make a complete the circuit and develop a potential difference. This in turn causes electron transfer between the electrodes, that is, from the anode to the cathode. Corrosion occurs due ti presence of this electron flow at the electrodes if the electrodes are made of metals that are responsive to corrosion. It is in these tests that show that the metals that a more effective electrochemical charge is cathodic and unreactive, so they are opposed to corrosion. On the other hand, the more the contrary the potential of a metal the more reactive its so being anodic and more responsive to corrosion (Wheeler, 1972. P. 79). From the above table of electrochemical cells potential difference, it is easier to determine the best metal to use that is not affected by an electrolyte when they are in contact. For instance, when you create a section with zinc and copper: The electrochemical difference of copper is +0.34 The electrochemical potential difference of zinc is -0.76 Therefore, the potential difference of this cell would be:  This experiment helps in determining the appropriate cell that may be best for synthesis of metals for use. 3. Objectives This experiment targets to analyse electrochemical potential for a variety of metals, used in construction, by measuring the potential difference exhibited during the establishment of a corrosion cell. 4. Hypothesis a. Null hypothesis Dissimilar metals always have a problem of cooperation in construction. Therefore, it is essential to avoid the constructions using dissimilar metals as this could lead to corrosion of these metals. As a result, they would start wearing out leading to failure in the structures. Else, you should try to use different metals in construction. b. Alternative hypothesis Sometimes metals combinations maybe used in structures provided they do not cause corrosion. 5. Methods and materials Apparatus 3 x 250ml plastic beakers Multimeter, leads, and clips Stands and clamps Tap Water Acidic solution (e.g. hydrochloric acid) Alkali solution (e.g. Sodium hydroxide solution) Metal samples (Aluminium, Brass, Copper, Lead, Mild Steel, Stainless steel, Zinc). Sand paper Indicator report (pH Paper) Procedure 1. I used the pH of the solution (the electrolyte) in container 1 and checked whether it is an acid, alkali or a neutral solution. I recorded this value in Table 2. 2. I took electrolyte PH in container 2 and identified whether it is an acid, alkali or a neutral solution. I recorded this value in Table 3. 3. I took the electrolyte PH in container 3 and identified whether it is an acid, alkali or a neutral solution. I recorded this value in Table 4. 4. Then I Cleaned all the metal samples with the sand paper. 5. I Arranged the equipment as shown in fig 1 below. 6. I selected 2 metal strips (initially this would be metals 1 and 2) and attached to the clips (metal 1 on the black terminal and metal 2 on the red terminal) and placed in container 1 and recorded the voltage. 7. I removed the metal and replaced with the next metal in the sequential order, placed in the electrolyte and recorded the voltage. 8. I repeated step 7 with the remaining metal samples. I recorded the voltages in the appropriate table. 9. Then I repeated the process with each on the metals on the black terminal and the remaining 6 metals on the red terminal, using the same electrolyte. 10. Lastly, I repeated the process with the 2 remaining electrolytes. This was to get better results from the experiment. Apparatus setup Fig 1: Apparatus set up. 6. Results From fig 1, when the electrochemical potential of each metal is obtained, it is easy to determine the desirable metal that you can use in your construction. In essence, the electrochemical potential of the given metal association may be vulnerable to calculate thus making it easier to for metal selection during construction is going on. The potentials above, shows the differences that metals have different electrochemical potentials ranging from negative to positive potential. This means that the more the metal is negative the higher the chances of the metal being prone to corrosion. While the more effective the material is the lesser the chances of being susceptible to corrosion. The following tables are a summary of the possible results obtained from the experiment using different metals strips in different electrolytes. POSITIVE (red terminal) GROUND (The Black terminal) Aluminium Brass Copper Lead Mild steel Zinc Stainless steel Aluminium -0.76 -0.80 -0.08 -0.53 -0.56 -0.45 Brass 0.77 -0.03 -0.68 -0.22 -1.26 -0.33 Copper -0.73 -0.06 -0.61 -0.13 -1.18 -0.20 Lead -0.06 +0.58 0.56 0.39 -0.64 0.30 Mild steel -0.49 0.20 -0.41 -1 -0.01 -0.21 Zinc 0.60 1.20 1.19 0.70 1 1.15 Stainless steel -0.28 0.25 0.23 -0.27 -0.05 -1.09 Table 2: results obtained using water as the electrolyte PH 7. Electrolyte PH 3 POSITIVE (red terminal) GROUND (The Black terminal) Aluminium Brass Copper Lead Mild steel Zinc Stainless steel Aluminium -0.56 -0.59 -0.21 -0.22 -0.33 -0.35 Brass 0.51 -0.08 -0.28 -0.26 -0.81 -0.08 Copper -0.57 -0.09 -0.35 -0.33 -0.88 0.08 Lead -0.20 0.36 0.35 0.03 -0.53 0.27 Mild steel -0.25 0.12 0.32 -0.02 -0.53 0.10 Zinc 0.31 0.80 0.88 0.55 0.55 0.75 Stainless steel -0.43 -0.05 0.09 -0.25 -0.22 -0.75 Table 3: results obtained using the acid as an electrolyte Electrolyte PH 12 POSITIVE (red terminal) GROUND (The Black terminal) Aluminium Brass Copper Lead Mild steel Zinc Stainless steel Aluminium 1.24 1.31 0.14 1.23 0.91 1.04 Brass -1.28 -0.02 -0.44 -0.29 -0.44 -0.28 Copper -1.30 -0.46 -0.14 -0.43 -0.28 -0.24 Lead -0.81 0.47 0.48 0.35 0.12 0.22 Mild steel -1.08 0.10 0.13 -0.33 -0.25 -0.12 Zinc -0.95 0.25 0.26 -0.19 0.09 -0.5 Stainless steel -1.05 0.25 0.28 -0.21 0.13 0.02 Table 4: results obtained using the alkali as an electrolyte. 7. Discussion From the tables of results obtained after using different electrolytes, it is clear that at any point where the electrodes are one metal material, the reaction for all metals is neutral regardless of the electrolyte in use. This means that if both electrodes were from the same material of a metal there would be no corrosion of the terminals of the cell. Electrolyte PH 7 This PH is essentially, the reference point PH. At PH 7 water is neutral thus if two different metals are dipped in water they usually react by dissolving water thus creating free electrons in the water. This in turn causes a current flow between the terminals. From this connection, the desirable characteristics of metals are determined to facilitate proper selection of the metals during construction of a structure. From table 3 and 4 the rate of reaction for all metals vary due to the presence of the Ph levels for the different electrolyte. For PH 3, the acid tends to dissolve most of the metals leaving the reaction to take place to replace the released electrons, thus creating a potential difference. 8. Conclusion As the metal location nears the top of the electrochemical potential difference table, the higher the chance that the metal will be more susceptible to corrosion. To the contrary, as the metal approaches the positive electrochemical side the higher the protection on the material against corrosion. This means that in electrochemical series, metals react as per their electrochemical p.d which in turn can aid determination of the appropriate choice that for construction. 9. Recommendations This process should entail high knowledge and well trained personnel with knowledge about the reactions involved. For the fore mentioned case, corrosion not only does it occur in presence electrolyte but also in cases where metals are in contact. When these metals undergo oxidation, reaction starts through lose of electrons from the metal which is more anodic to the cathodic metal. To avoid these scenarios proper measure should be taken to prevent the rate of corrosion in these metals (Jones, 1996. P. 110). These methods to control corrosion include anode protection, cathode protection, anodization, and reactive coatings. 10. References and Bibliography Wheeler, G. J. (1972). The design of electronic equipment: a manual for production and manufacturing, New Jersey: Prentice-Hall Jones, D. (1996). Principles and Prevention of Corrosion (2nd edition ed.), New Jersey: Prentice Hall. Read More

For instance, when you create a section with zinc and copper: The electrochemical difference of copper is +0.34 The electrochemical potential difference of zinc is -0.76 Therefore, the potential difference of this cell would be:  This experiment helps in determining the appropriate cell that may be best for synthesis of metals for use. 3. Objectives This experiment targets to analyse electrochemical potential for a variety of metals, used in construction, by measuring the potential difference exhibited during the establishment of a corrosion cell. 4. Hypothesis a.

Null hypothesis Dissimilar metals always have a problem of cooperation in construction. Therefore, it is essential to avoid the constructions using dissimilar metals as this could lead to corrosion of these metals. As a result, they would start wearing out leading to failure in the structures. Else, you should try to use different metals in construction. b. Alternative hypothesis Sometimes metals combinations maybe used in structures provided they do not cause corrosion. 5. Methods and materials Apparatus 3 x 250ml plastic beakers Multimeter, leads, and clips Stands and clamps Tap Water Acidic solution (e.g. hydrochloric acid) Alkali solution (e.g. Sodium hydroxide solution) Metal samples (Aluminium, Brass, Copper, Lead, Mild Steel, Stainless steel, Zinc).

Sand paper Indicator report (pH Paper) Procedure 1. I used the pH of the solution (the electrolyte) in container 1 and checked whether it is an acid, alkali or a neutral solution. I recorded this value in Table 2. 2. I took electrolyte PH in container 2 and identified whether it is an acid, alkali or a neutral solution. I recorded this value in Table 3. 3. I took the electrolyte PH in container 3 and identified whether it is an acid, alkali or a neutral solution. I recorded this value in Table 4. 4. Then I Cleaned all the metal samples with the sand paper. 5. I Arranged the equipment as shown in fig 1 below. 6. I selected 2 metal strips (initially this would be metals 1 and 2) and attached to the clips (metal 1 on the black terminal and metal 2 on the red terminal) and placed in container 1 and recorded the voltage. 7. I removed the metal and replaced with the next metal in the sequential order, placed in the electrolyte and recorded the voltage. 8. I repeated step 7 with the remaining metal samples.

I recorded the voltages in the appropriate table. 9. Then I repeated the process with each on the metals on the black terminal and the remaining 6 metals on the red terminal, using the same electrolyte. 10. Lastly, I repeated the process with the 2 remaining electrolytes. This was to get better results from the experiment. Apparatus setup Fig 1: Apparatus set up. 6. Results From fig 1, when the electrochemical potential of each metal is obtained, it is easy to determine the desirable metal that you can use in your construction.

In essence, the electrochemical potential of the given metal association may be vulnerable to calculate thus making it easier to for metal selection during construction is going on. The potentials above, shows the differences that metals have different electrochemical potentials ranging from negative to positive potential. This means that the more the metal is negative the higher the chances of the metal being prone to corrosion. While the more effective the material is the lesser the chances of being susceptible to corrosion.

The following tables are a summary of the possible results obtained from the experiment using different metals strips in different electrolytes. POSITIVE (red terminal) GROUND (The Black terminal) Aluminium Brass Copper Lead Mild steel Zinc Stainless steel Aluminium -0.76 -0.80 -0.08 -0.53 -0.56 -0.45 Brass 0.77 -0.03 -0.68 -0.22 -1.26 -0.33 Copper -0.73 -0.06 -0.61 -0.13 -1.18 -0.20 Lead -0.06 +0.58 0.56 0.39 -0.64 0.30 Mild steel -0.49 0.20 -0.41 -1 -0.01 -0.21 Zinc 0.60 1.20 1.19 0.70 1 1.15 Stainless steel -0.28 0.25 0.23 -0.27 -0.05 -1.09 Table 2: results obtained using water as the electrolyte PH 7.

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