Corroded Iron Nails
Conservation of Corroded Iron Nails Rebecca Christensen Partner: Tegan Zurbo Semester 3 2011 Aim The purpose of this extended experimental investigation is to explore the optimum conditions for restoring rusted iron. By chemically preserving a rusted nail, the methods used aim to simulate the ways in which marine artefacts are restored. Theory Corrosion occurs very rapidly in marine environments due to the optimum conditions for metals to rust.
Both water and oxygen are necessary for rust to form as well salt accelerates rusting, due to this rapid acceleration the ability to reverse the effects of corrosion of metal objects immersed in sea water is a necessity. Variables including temperature, pH and the presence of chloride are involved in corrosion in marine environments and considerable impact on the rate and type of corrosion that occurs. The metal being studied in this investigation, iron, is one of the most challenging of all metals to conserve. Metal corrosion occurs as a reduction and oxidation (redox) reaction.
In this situation, oxidation can be defined as the loss of electrons or the gain of oxygen in going from reactant to product. Reduction can be defined as the gain of electrons or the loss of oxygen in going from reactant to product. Both processes occur simultaneously throughout the reaction. Corrosion of iron that occurs in a marine environment is a process called electrochemical corrosion the process of rust formation is virtually a galvanic cell. At a weak point on the iron surface iron atoms lose electrons to form Fe2+ ions: Fe -> Fe 2+ (aq) + 2e- These sites of oxidation are known as anodic sites.
The electrons flow from these sites through the iron to an area of the iron that contains an impurity such as carbon, this impurity may act as a cathode, these electrons then reduce the oxygen that is surrounding the iron in the water. Fe2+ (aq) + 2OH- (aq) Fe (OH) 2 (s) Sites where this reduction is caused are called cathodic sites. The ions migrate from one location on the irons surface to another through the moisture surrounding the artefact, due to the conduction ability of salt water the rusting process occurs much faster in salt water than in fresh water.
This migration of irons preserves electrical neutrality within the galvanic cell by pushing Fe2+ and OH0 together which forms insoluble iron hydroxide: Fe2+ (aq) + 2OH- (aq) Fe (OH) 2 (s) Iron hydroxide is oxidised to iron forming rust: 4Fe (OH) 2(s) + O2 (g) 2(Fe203H20) (s) + 2(H20)(l) Figure [ 1 ] Galvanic Corrosion Archaeological iron is usually covered by a layered structure of corrosion products. The outer layer is a mixture of iron corrosion products (e. g. iron(III) oxyhydroxides, typically goethite) and extraneous material such as small rocks, sand, clay and soil minerals.
Below this is another layer of iron corrosion products in a lower oxidation state, usually magnetite, lying on top of any remaining metal. When iron corrodes in a marine environment, it usually becomes covered with concretions, primarily calcium carbonate CaCO3. The Fe2+ ions tend to react and precipitate in the concretion rather than on the surface of the object. The net result of on-going iron corrosion in marine environments is that the cracks, pores, and open spaces within the corrosion layer or beneath concretion become filled with an acidic iron(II) chloride solution, with the Cl- ions concentrated at the metal surface (Turquoise 1993).
The experiment has been based around the National Museum of Australia’s method of conserving iron objects. The artefact collected is conserved by storing the object submerged in an alkaline solution from the point it is taken from the ocean this prevents any further reactions from taking place, the removal of the Cl- minimises the further corrosion of the artefact. In order to restore the corroded object the museum then uses an electrolytic cell, a process that involves the use electrical energy to force a non-spontaneous redox reaction.
In this reaction, the iron artefact is the cathode and the oxidizing metal is the anode, the anode causes the iron to gain electron and become reduced to iron metal. Figure [ 2 ] An Electrolytic Cell Reaction at Cathode: Fe2+ + 2e- Fe The oxygen ions from the iron oxide enter the electrolyte solution. The oxidizing metal (using copper as an example) is oxidized and loses electrons. Reaction at Anode: Cu Cu2+ + 2e- The copper ions enter the electrolyte solution while the spare electrons combine with the iron ions.
Once the redox reaction is completed to a satisfactory standard, the reduced iron metal is washed, dried, sprayed with a stabilizer and dipped in molten wax. Other methods for restoring corroded iron include soaking the artefact in an acid solution for a set amount of time. The acid reacts with the iron dissolving it and if left in for an extended period of time would eventually dissolve the artefact itself. The following equation represents this reaction: Fe2O3(s) + Fe(s) + 6HCl (aq) 3FeCl2(s) + 3H2O (l)
The acid causes a double displacement reaction which would continue until the The hydrochloric acid causes a double displacement reaction which would continue until all of the iron and iron oxide had been converted to a waste solid of ferric chloride. This method is potentially effective so long as the iron object is removed from the solution before the acid has time to dissolve the iron metal. However, this conservation method only removes the rust and does not restore the iron object like the Museum’s method does. Experimental Design
Hypothesis: It is predicted that the use of an alkaline bath, a moderately high voltage of 10V and the longest possible period of time at 50 minutes of electrolysis will achieve the ultimate rust reduction of an iron nail. Risk Assessment: Some of the chemicals used during the experimental processes were potentially hazardous. Refer to Appendix 1 for a risk assessment sheet. Managed Refinement: To ensure managed refinement of the investigation, Table1 was formed to monitor all variables throughout the experimentation. Set 1;Sodium Hydroxide Rinse| Set 3;Voltage| Set 3;Times| | Yes| No| 2V| 4V| 6V| 10V| 20 minutes| 40 minutes| 60 minutes| Rinse| Independent| Independent| Dependent on results of set 1| Dependent on results of set 1| Dependent on results of set 1| Dependent on results of set 1| Dependent on results of set 1| Dependent on results of set 1| Dependent on results of set 1| Time in Electrolysis| 20 minutes | 20 minutes| 20 minutes| 20 minutes| 20 minutes| 20 minutes| Independent| Independent| Independent| Voltage| 4V| 4V| 2V| 6V| 8V| 10V| Dependent of results from set 2| Dependent of results from set 2| Dependent of results from set 2| ElectrolyteSolution| Sodium Hydroxide| Sodium Hydroxide| Sodium Hydroxide| Sodium Hydroxide| Sodium Hydroxide| Sodium Hydroxide| Sodium Hydroxide| Sodium Hydroxide| Sodium Hydroxide| ConcentrationOf Electrolyte| 0. 5 M| 0. 5 M| 0. 5 M| 0. 5 M| 0. 5 M| 0. 5 M| 0. 5 M| 0. 5 M| 0. 5 M| Amount ofElectrolyte| 240mL| 240mL| 240mL| 240mL| 240mL| 240mL| 240mL| 240mL| 240mL| Size of Beaker| 250mLBeaker| 250mL Beaker| 250mL Beaker| 250mL Beaker| 250mL Beaker| 250mL Beaker| 250mL Beaker| 250mL Beaker| 250mL Beaker| Temperature| Room Temp| Room Temp| Room Temp| Room Temp| Room Temp| Room Temp| Room Temp| Room Temp| Room Temp| Size and type of Nail| 75 x 3. 75mm 6. 8g| 75 x 3. 75mm 6. 8g| 75 x 3. 75mm 6. 8g| 75 x 3. 75mm 6. 8g| 75 x 3. 75mm 6. 8g| 75 x 3. 75mm 6. 8g| 75 x 3. 75mm 6. 8g| 75 x 3. 75mm 6. 8g| 75 x 3. 75mm 6. g| Rust on Nail at Start of Exp| Unable to Control| Unable to Control| Unable to Control| Unable to Control| Unable to Control| Unable to Control| Unable to Control| Unable to Control| Unable to Control| Anode| Stainless Steel| Stainless Steel| Stainless Steel| Stainless Steel| Stainless Steel| Stainless Steel| Stainless Steel| Stainless Steel| Stainless Steel| Time in Rinse| 24hrs| N/A| 24hrs| 24hrs| 24hrs| 24hrs| 24hrs| 24hrs| 24hrs| Concentration of Rinse| 0. 5 molar| N/A| 0. 5 molar| 0. 5 molar| 0. 5 molar| 0. 5 molar| 0. 5 molar| 0. 5 molar| 0. 5 molar| Amount of Rinse| 180mL| N/A| 200mL| 200mL| 200mL| 200mL| 200mL| 200mL| 200mL| Materials The following materials list was used as a basis for each experiment and modified when required for each independent variable. * 2 x 250ml beakers * 1 rusted nail (for each experiment) * Scientific scales NaOH powder * Di-ionized water * 1 volumetric flask * Wooden Clips/ electrode holders * Power pack (2V-10V) * 2 x alligator clips * Stainless Steel Anode Method 1. The nail mass was measured and recorded using the scientific scales. 2. 500mL of 0. 5M NaOH was made by dissolving 10g of naOH with 500mL of distilled water in a volumetric flask. 3. To create a rinsing bath, one 250mL beaker was filled with 200mL of 0. 5M NaOH. 4. The nail was placed in the rinsing bath and left overnight. 5. A beaker was filled with 240mL of 0. 5M NaOH. 6. The nail and anode were secured on the edges of the flask ensuring that the anode and cathode were not touching. 7.
The electrodes were attached using alligator clips to the power pack. (Anode to positive terminal and nail to negative terminal) 8. The power pack was set to the voltage specified for the experiment (2V, 4V, 6V or 10V) 9. The electrolytic cell was left to react for the required time of the experiment (10 min, 20 min, 50 min. 10. The nail was dried with paper towel and weighed once more. The weight was recorded. Figure 3 An Electrolytic Cell from one of Many Experiments Variable Control * In order to produce reliable experimental results, several variables were controlled as accurately as possible. Type/Amount/Concentration of Rinse Solution (NaOH (aq)) The same type of rinse solution, NaOH (aq) was used for each experiment for each experiment exactly 200mL of NaOH was measured out in a beaker with measurement markings. The concentration of the rinse solution was controlled by using scientific scales to precisely measure out the mass of sodium carbonate required. Professional volumetric flasks were used to measure the distilled water. Size and Type of Anode * For every experiment (excluding experiment 6) a stainless steel rod was used as an anode. * Different anodes have different electrical capabilities and the use of different anodes would affect the current running through the electrolytic solution. Voltage The voltage during electrolysis was set according to the specifications of the experiment. For experiments where voltage was not an independent variable, it was ensured that the voltage was kept at 4V. * The voltage used in an experiment may affect the results if voltages are altered in an uncontrolled manner as the higher the voltages the quicker the rust would be removed. Type/Amount/Concentration of Electrolyte Solution * Beakers with measured markings were used carefully to make sure 240mL of electrolyte was used in the experiment. However, the beakers were only marked up to 200mL so the extra 40mL (used to submerge nail as best as possible) was measured very approximately.
The concentration of the electrolyte solution was controlled by using scientific scales to weigh the amount of sodium carbonate though these measurements may have been out by a few grams due to the inaccuracy of the scales. Professional volumetric flasks were used to measure the distilled water. Size of Beaker * With every experiment throughout the investigation a 250mL beaker were used. * The same size beaker must be used to control the experiment as the higher the electrolyte to artefact volume the longer period of electrolysis required. Temperature * The temperature of the experiment was not controlled; it was too difficult to control temperature as the electrolysis process changes the temperature of the solution. If the temperature is not controlled throughout the experiment as temperature speeds up the process of electrolysis. Size and Type of Nail * It was ensured that all of the nails used during experimentation were the same type and approximately the same size. The weight varied slightly in each nail due to the different levels of rusting. * The size of the nail may affect an experiment if it has a larger capacity than a smaller nail, as the higher the electrolyte to artefact volume the longer period of electrolysis required. Rust on Nail at Start of Experiment * The rust on the nail could only be estimated through observation as the nails had come from a range of places were the rusting process was not a controlled experiment. The condition of the nail may have affected the experiment as the amount of time required for a nail with a high corrosion level would be a lot higher than the time needed for a nail that has a low level of corrosion. Time in Electrolysis * To ensure that the time of electrolysis was accurate a stopwatch was to be used, this ensured a very accurate time reading through all the experiments. There were minor errors in the time in higher voltage experiments when the power pack temporary turned off these times were approximately compensated for though not accurately. Time in Rinse * The amount of time the nail remained in the nail bath was a difficult variable to control each nail was left in the rinse bath for approximately one night though the time varied by a few hours due to class schedules. The time in rinse may have affected the final results as the rinse bath is only effective if it is allowed enough time to diffuse all Cl- ions present in the corroded artefact, if one experiment is not allowed enough time for the rinse bath that experiment may be less effective than another. Exposure to further corrosive environments * Between experiments the nails were stored in reasonably airtight sealed bags to reduce further exposure to oxygen which would cause further corrosion. RESULTS Table 2 Qualitative observations of each experiment Experiment | Qualitative Results| (1) RinseStainless Steel Anode 4 Volts20 mins| * Vigorous bubbling at cathode, bubbling appeared to detach rust from nail. * Faint sighting of H2 gas diffusing into air. It only took a couple of minutes for silver iron to become visible. | (2) No RinseStainless Steel Anode4 Volts 20 mins| * Vigorous bubbling, bubbling didn’t cause rust to detach from nail * Faint sighting of H2 gas diffusing into air. * Once nail was dried, not as much red rust had been removed than in experiment 1. | (3)2V VoltsStainless Steel AnodeRinse20 mins| * Less bubbling produced at cathode compared to previous experiments with 4V thus little rust was seen flaking off nail. * Once nail was dried, magnetite appeared along nail’s surface along with non-restored red rust. | (4)6V VoltsStainless Steel AnodeRinse20 mins| * Very vigorous bubbling, H2 gas was seen diffusing into air.
Iron oxide detached from nail quicker due to forceful bubbling. * Once nail was dried, magnetite could be seen on the surface of the nail, a much greater percentage than with 2V (experiment 3) * Very minimal amount of red rust present on nail. | (5)10VStainless Steel AnodeRinse20 mins| * More bubbling and H2 gas were produced compared to experiment 4. * Once nail was dried, the surface appearance resembled closely to the appearance of the nail in experiment 4, although there was no red rust visible. * Slightly more magnetite present on nail than in experiment 4. | (6)10VStainless Steel AnodeRinse10 min| * Vigorous bubbling, causing rust to detach from nail. * H2 gas seen diffusing into air. Once nail was dried, there was still a fair amount of red rust present and slight areas covered in magnetite * During electrolysis, electrolyte turned cloudy and yellow, brown staining was now visible on stainless steel anode| (7)10VStainless Steel anodeRinse50 min| * Vigorous bubbling, causing rust to detach from nail. * H2 gas seen diffusing into air. * Once nail was dried, there were barely any visible areas of shiny metal. The nail had barely any rust left on it, but was covered in magnetite. | Table 3 Quantitative observations from each experiment Quantitative Results| Experiment| Mass Before | Mass After| Change in Mass| Observations| (1) Rinse| 6. 74g| 6. 71g| -0. 03g| 80% Black coating10% Red rust 10% Shiny Steel| (2) No Rinse| 6. 77g| 6. 76g| -0. 01g| 50% Black coating40% Red rust 10% Shiny Steel| (3) 2V| 6. 7g| 6. 76g| -0. 01g| 30% Black coating60% Red Rust 10% Shiny Steel| (4) 6V| 6. 76g| 6. 72g| -0. 04g| 79% Black coating1% Red Rust 20% Shiny Steel| (5)10V| 6. 81g| 6. 74g| -0. 07g| 80% Magnetite20% Shiny Steel| (6)10min| 6. 74g| 6. 74g| 0g| 55% Black coating40% Red Rust 5% Shiny Steel| (7) 50min| 6. 77g| 6. 70g| -0. 07g| 95% Black coating 5% Shiny Steel| Figure [ 4 ] Graphical Comparison of NaOH Rinse Figure 5 Graphical Comparison of Times Figure 6 Graphical Comparison of Voltages Figure [ 7 ] Visual Time Comparison 20/50 Minutes Images of Results Figure 8 Visual Voltage Comparison 2V, 6V, 10V Figure [ 9 ] Visual Comparison Use of Alkaline Bath
As the investigation proceeded, the variables that produced the best results were adopted for the rest of the investigation as a way of experimental optimization. For instance once it was clear that the NaOH rinse improved the results (after experiment 2), a NaOH rinse was used for each subsequent experiment. The second variable that was tested was the voltage, the voltage was lessened from 4V to 2V though this voltage was not high enough and the reduction of rust was less so the voltage was increased to six volts which was deemed more successful to experiment this trend we experimented with 10V which was even more successful and was adopted for the time experiments.
For the time experiments the time of electrolysis was reduced to 10 minutes as hypothesised this reduced the rust reduction of the iron. An outlying ‘extreme’ experiment was tested at 50 minutes electrolysis though this experiment reformed all iron as magnetite resulting in only 5% restoration. Trends in Results In experimenting the independent variables throughout the experiment there were an obvious trend in the results. The first variable was of the alkaline bath which in text 1 and 2 was confirmed to increase the level of reduction and reconstruction of the nail. The second variable was of the voltages, it was seen that the lower voltages 2 & 4 did not have as large an impact on the rust reduction of the nail as the higher voltages 6 & 10.
The final variable was of the time of electrolysis experiments 5, 6 & 7 it was originally thought that the longest period of time for electrolysis would have been the most effective though it was apparent that experiment 6 which was at a period of time of 30 minutes achieved the ultimate restoration. All experiments had a black coating over the entire or partial area of the nail, this was presumed to be magnetite, Fe3O4 , an oxide of iron. Magnetite is an intermediate product in the reduction of rust back to iron metal. Anomalies In the 6th experiment the solution turned yellow and brown substances were deposited on stainless steel anode. There is no conclusive evidence on why either of these reactions took place.
There are two possible explanations to why these reactions took place: The first possible explanation is that the second anode used was contaminated with another substance or was an impure metal causing the contamination in the reaction. The second possible explanation was that there was an impure substance or another metal present in the corroded nail. It is possible that the unknown substance in the nail reacted with the electrolyte causing the brown layer to be deposited on the stainless steel anode. This experiment was not recorded in the final results as it was not reliable, whatever occurred within the experiment was completely accidental and even though the final results were very successful variables must have been altered to have resulted in this anomaly. Discussion
None of the experiments fully restored the iron nails to their original state though most experiments achieved a high level of restoration. All experiments achieved at removing a high percentage of rust removal though the experiments were not successful at restoring the nails with a metallic appearance, only a few partially achieved this and even the most optimum experiment with the shiny iron was covered in a black coating presumed to be magnetite. The alkaline rinse was a highly contributing element in the restoration of the nail, the idea to use the alkaline bath for the experiment was taken from the Australian Museum website which was thought to be a reliable source and would be an effective addition to improve the results. The alkaline bath as the first variable tested in experiments 1 and 2 and from the results of these experiments it was clear that the alkaline bath had aided in the restoration of the rinsed nail even though both nails achieved the same percentage of shiny metal, the un-rinsed nail had a much higher level of red rust remaining at 40% red rust whereas the high percentage of surface area on the rinsed nail was composed of black coating at 80% which was presumed to be either iron oxide or magnetite. During the electrolysis of the rinsed nail in the first experiment it was observed that the rinsed nail immediately began to shed large flakes quickly whereas the un-rinsed nail lost the particles of rust slower and in smaller sections.
The explanation for this suggests the rinse had weakened the lattice of the rust layer. There are several explanations for why this result occurred. The most plausible explanation for this occurrence is that the Cl- ions in the Fe2O3(s) lattice left over from the NaCl (aq) could have been removed by the NaOH which would have reduced any subsequent reactions between the iron and Cl- ions. The H2O in the Fe2O3(s) lattice could have been removed by the NaOH (aq). Both of these processes weaken the lattice making the nail more susceptible reconstruction through electrolytic reduction. The most likely occurrence is that both of the above estimations occurred with the rinse baths conducted.
The H20 was removed from the rust by the Na + and OH- ions through diffusion. There was no apparent reaction that occurred through the rinse bath as the appearance of the nail as well as the appearance and colour of the solution had no changes. When voltage was tested as a variable the tests concluded that the higher the voltages the quicker the rust was removed from the iron. It was concluded that 10V was the most effective experiment due to increased voltages increase the flow of electrons and increase the rate of electrons in turn increasing the rate of the electrochemical reactions. The higher the voltage the easier it is for the migration and the further distance it will be able to travel between electrodes.
This was apparent in the visual acceleration of the experiment, the 10V experiment had vigorous bubbling at the cathode reducing the oxygen surrounding the nail and ultimately causing the rust to detach from the nail immediately. The increased voltages also resulted in a higher level of hydrogen gas production at the cathode. The increased amount of gas produced at the cathode would have helped to forcefully remove the outer rust layer. The half reactions that demonstrate this gas production are: 2O2-? 4e- + O2(g) (gas production at anode) 2H+ + 2e- ? H2(g) (gas production at cathode) The reactions at the electrodes use free electrons passing through the circuit to form covalently bonded gas molecules. The gas molecules ultimately disrupt the Fe2O3 layer’s attachment to the surface of the iron nail causing it to flake off.
However, it is unknown whether all the Fe2O3 detaches or whether the ionic bond between the Fe3+ ions and the O2- ions is somehow broken to enable the Fe3+ ions to be reduced/restored to Fe(s). The formation of magnetite occurred once the nail came into contact with atmospheric oxygen. Magnetite (Fe3O4) would have formed through the oxidation of unrestored Fe3+ ions to Fe4+ ions along the nail’s surface. Because 10V produced more magnetite, more Fe3+ ions must have been evident on the nail’s surface. 6V reduced more Fe3+ ions but was not as efficient as the 10V at separating the Fe3+ ions and the O2- ions within the bonded rust to make them available for oxidation/reduction.
The Time of Electrolysis Hypothesis was that the longer the time of electrolysis the longer time the artefact would be allowed for a complete reaction thus resulting in a better reduction. For electrolysis to be effective the artefact must be allowed enough time to diffuse all Cl- ions from the corroded layer, if this is not done not only is the nail not restored the corrosion process has not been stopped and the artefact will continue to rust. When artefacts are clean using electrolytic reduction in small vats with a low ratio of electrolyte to artefact volume, the length of electrolysis time is considerably extended. The larger the volume of electrolyte to artefact being cleaned, the shorter the period of electrolysis required.
In the time experiments two different times were experimented not including the experiments conducted earlier. The 10 minute experiment was quite unsuccessful as predicted it did not achieve much restoration and was unable to remove 40% of the red rust on the exterior of the nail. The 50 minute experiment appeared to be quite unsuccessful due to its black appearance though this was not the case, magnetite is a substance that is quite loose on the surface and would have brushed away when touched, the surface of the nail was relatively smooth suggesting the nail had efficient time in order to restore the nail with reformed iron deposits, resulting in almost complete restoration. Conclusion
In conclusion the most effective environment for reduction of iron using electrochemical corrosion consists of a high voltage, extended period of time and the use of a rinse bath in exception to their conditions. The rinse bath was obviously beneficial within our secondary data as it was predicted from primary data; the bath was beneficial due to its effects of diffusing of the corrosive Cl- ions from the outer layer of the corroded artefact. The most extended period of time was concluded as the most effective due to the results of the experiments that the nail achieved the highest level of total restoration at 50 minutes the longest experiment conducted. The reason for this restoration is the longer the time the artefact is allowed the higher the ability to diffuse all Cl-ions as well as having time to restore all layers of corrosion.
The highest voltage at 10V used was concluded as the optimum voltage to use in restoration of the artefacts as it was able to remove all rust without having an effect on the artefact itself. The results supported our research as it was predicted a higher voltage results in a speedier reduction reaction causing the nail to be restored faster. Evaluation: Our hypothesis that a moderate voltage, extended period of time of electrolysis to volume capacity and the use of an alkaline bath will result in the highest level of reduction was relatively supported by our secondary data. The highest level of restoration was achieved with these components with our optimum test removing all red rust from the nail although a metallic sheen was restored.
While our hypothesis was supported by our experimental data this investigation could have been further extended in order to back up our experimental results and different variables could have been further experimented on Limitations and possible errors There were a number of complications throughout the experiments causing a lack of accuracy throughout the results. Limitations to these experimental results include the following: * The experiments were not replicated. If they were repeated the results could have differed. Controlled experiments usually include replication so that any variation can be assessed, ultimately enabling more reliable comparisons between experiments. The amount of time that each nail spent in the NaOH rinse should have been controlled more carefully as some nails were rinsed for much longer than other nails. * The scales were not accurate for the first sets of results so the weights recorded both after and before the electrolysis are most likely inaccurate as well as the amounts of NaOH solution used, as the scales were not reading properly the NaOH powder was hard to measure in order to provide a reliable concentration over all of the experiments. * It was too difficult to experiment on other variables in order to increase the information of the experiment due to the lack of equipment e. . anaerobic conditions, temperature conditions. Recommendation: If this experiment was to be completed there would be a number of factors of the experiment that need to be altered. To ensure all variables were controlled the duration of the NaOH bath should be required for the same period of time for all experiments, the nails should be rusted in a controlled environment to ensure that each nail is of approximate same corrosion and there are no impure substances present and more sensitive scales should be used in order to receive accurate readings as well as ensure an equal concentration of the electrolytic solution throughout all experiments.
There are also other factors that could have been experimented in order to inquire more information of the reduction process, variables such as temperature, anaerobic conditions and the anode substance could be experimented with in order to further improve the reduction process. There were limitations with time during the experiment and in order to further improve them the experiments could have been extended in order to allow more time to repeat the experimentations as well as experiment further with the chosen variables. Bibliography 1. Chemistry Department, (2008) Corrosion, <http://library. kcc. hawaii. edu/external/chemistry/everyday_corrosion. html>, University of Hawaii. (accessed 10th March 2011) 2. Corrosion Doctors, Rust Chemistry, < http://corrosion-doctors. org/Experiments/rust-chemistry. htm 3. >. (accessed 5th March 2011) 4.
Hamilton D, (2000) File 9: Metal Conservation: Preliminary Steps, <http://nautarch. tamu. edu/class/anth605/File9. htm>, A and M University, Texas. (accessed 10th March 2011) 5. Hochstetler, S and Tindall B, (28/03/2004) The Chemistry of Cleaning Rusted Iron by Electrolysis, < http://www. holzwerken. de/museum/links/electrolysis_explanation. phtml 6. >. (accessed 20 April 2011) 7. Treible, G. W, (09/03/2003) Engineering Report: Electrolytic Rust Removal, <http://www. davidbradley. net/ERR. html>, David Bradley Manufacturing, Pennsylvania. (accessed 20 March 2011) 8. Proceedings of Metal (2004) Overview of archaeological iron <http://www. nma. gov. u/shared/libraries/attachments/publications/metal_04_proceedings/section_3_better_understanding_of_treatments/files/7844/NMA_metals_s3_p06_overview_archaeological_iron. pdf> (Accessed 30 March 2011) 9. (Classroom Handout) Redox Reactions of a galvanic cell * Wilbraham, A; Staley, D; Matta, M; Waterman, E. (2002) Chemistry, United States of America: Prentice Hall. (Classroom text book) Appendix One: Risk Assessment Form Preparation/experiment/activity: Reduction of Corroded Nails| Hazardous Substances:| Substance| Hazard| MSDS Available| Sodium Hydroxide (NaOH)| Health Rating: 3 – Severe (Poison) Flammability Rating: 0 – None Reactivity Rating: 2 – Moderate Contact Rating: 4 – Extreme (Corrosive) Inhalation: Severe irritant.
Effects from inhalation of mist vary from mild irritation to serious damage of the upper respiratory tract, depending on severity of exposure. Ingestion: Corrosive! Swallowing may cause severe burns of mouth, throat, and stomach. Severe scarring of tissue and death may result. Skin Contact: Corrosive! Contact with skin can cause irritation or severe burns and scarring with greater exposures. Eye Contact: Corrosive! Causes irritation of eyes, and with greater exposures it can cause burns that may result in permanent impairment of vision, even blindness. | YES| Procedure/Summary of Experiment:| Restoring rusted iron by: rinsing iron in NaOH and placing nail in an electrolytic cell with different voltages and times. | Risks Identified:| Control| PPE (Please Specify)|
Handling Chemicals| Use fume hood when appropriate; use protective wear including gloves, goggles, tongs and closed in shoes to prevent skin contact. If skin contact does occur immediately rinse the area. If contact occurs with the eye area immediately use the eye wash station. If substance is inhaled or ingested medical attention will be required. | Gloves, safety goggles, closed in shoes tongs. | Using Electricity| Don’t allow water or flame near the power source, Do not allow electrodes to touch, and do not submerge electrodes or leads to protect from electrocution. | Gloves, safety goggles. | Other Issues: Production of hydrogen gas. Hydrogen and air mixtures can be explosive, keep any igniting properties away from any hydrogen gas production in order to prevent explosive reactions. Conclusion about Risks: LOW provided that all safety procedures are carried out. | Disposal of Waste: Chemicals can be disposed of by the sink when mixed with a large quantity of water as long as waste contains no heavy metals. Anodes can be rinsed in water and reused. | Staff Involved in Assessment: Checked by:Date: Note: This assessment is valid for a period of five years from the date above. See overleaf to sign that you have checked the relevant MSDS’ and this risk assessment. Appendix Two: Declaration I, Rebecca Christensen, declare that this report is my own work. Student’s Signature: ___________________________ Parent’s Signature: _____________________________