Electrochemistry

Scenario

The shipwreck of the RMS Gargantuan has just been discovered! In most ways, this shipwreck is nearly identical to the shipwreck of the RMS Titanic. The Gargantuan was built at around the same time as the Titanic, and shipbuilders used the same materials in their construction.

Because the two ships were found at similar depths and under similar oceanic conditions, conservators working with metal artifacts and pieces of the hull from the Gargantuan shipwreck will face many of the same challenges as did those who were involved with the Titanic recovery efforts.

What are those challenges? How can corroded metals be preserved and restored with the minimum damage? How do electrochemistry and redox reactions play a crucial role in recovering metal artifacts from shipwrecks?

Challenge

Divide your class into groups. You are chemistry consultants called to the task force meeting to plan the preservation and restoration of the hull and artifacts from the RMS Gargantuan. The task force comprises other scientists, museum conservators, and key members of the recovery team.

First, your group will do research to find out about the chemistry of the ocean, the nature of the shipwreck, materials used in shipbuilding, and the chemistry of the restoration and conservation of materials recovered from shipwrecks. You will probably want to split up the research so that each person in the group has a topic to research.

The group will also design and carry out an investigation related to the RMS Gargantuan recovery project. You will prepare a laboratory report to summarize your findings.

Finally, the group will prepare an information folder that includes the laboratory report and findings from the research. Each group will present the results of their investigation.

Part A: Research
Research the conditions under which the Gargantuan was found (oceanic depth, temperature, etc.). You can assume that the Gargantuan was found under identical conditions to the Titanic. Summarize the information you find in point form.

Research shipbuilding materials through history.

• Identify data and gather and process information from secondary sources to trace the historical developments in the design and construction of oceangoing vessels for the past 150 years. Provide a historical account of the design and construction of ocean going vessels with a focus on metals used. Summarize your information on a timeline.
• Use a variety of resources to research the composition of steel and explain how the composition of steel affects its properties, such as its strength and resistance to corrosion. Record this information in a chart.

Find out about the materials used to build the hull of the Titanic. Assume the Gargantuan used similar materials. Create a list with a brief description of each material.

Find out how shipbuilders try to protect hulls from corrosion.

Provide a description of ways in which the metal hull of a ship may be protected including use of surface alloys, corrosion of resistant metals, and new paints.

Describe the process of cathodic protection, providing examples of its use in both marine environments and including an explanation of the redox chemistry involved.

Find out about the chemistry of the ocean environment.

• Identify some key solutes dissolved in the oceans and discuss their concentrations at varying depths of the ocean. Outline the effect of temperature and pressure on the solubility of various compounds in the ocean.
• Discuss the varying solubility of gases at increasing depths of the ocean. Does the different solubility of gases in the ocean affect the rate of corrosion of metal objects in the ocean?

At very great depths, wrecks corrode due to the action of anaerobic bacteria. Do research to explain why these sulfur-reducing bacteria accelerate corrosion of some metals.

Research the chemical methods available to analyze metal materials found at shipwrecks.

Investigate methods used to restore and conserve recovered ships or metal artifacts found with shipwrecks. Discuss the redox chemistry involved.

Part B: Testing and Inquiry

Each group should design an experiment to investigate a different question about metal corrosion. The question must relate to the protection of ships, the corrosion of shipwrecks, or the conservation and restoration of ships or artifacts from shipwrecks. The question must also relate to redox chemistry. Some suggestions for topics are provided below. You may also come up with your own topic. Be sure to include a hypothesis and/or prediction in your experimental design. Make sure you review MSDS sheets for all substances involved and list all safety precautions.

Have your procedure approved by your teacher before you begin to work in the lab.
Perform an investigation into the conditions required for rusting to occur.

• Compare the rate of corrosion for different metals and alloys, such as iron, copper, aluminum, and steel.
• Compare the corrosion rate of an unprotected metal with a variety of metals that have been protected in some way.
• Perform an investigation to compare and describe the rate of corrosion of submerged metals in different temperatures, or in different salt concentrations.
• Design an experiment to determine the effect of pH on the rate of corrosion of metals in solution.

Investigate different ways to use redox chemistry to restore salt-saturated artifacts or to clean corroded objects.

Part C: Analyze and Reflect
Draw conclusions based on the results of your experiment. Discuss your conclusions with your group.
Analyze your investigation in terms of your hypothesis and/or prediction. Can your hypothesis explain your results? Did your results match your prediction?

Write a complete laboratory report. Include the following:

introduction
hypothesis and/or prediction
procedure
data/observations
conclusions
discussion

As part of your discussion, ensure you do the following:

demonstrate your knowledge of redox chemistry

relate the results of your investigation to a specific aspect of shipbuilding, the corrosion of shipwrecks, or the restoration and preservation of artifacts from shipwrecks

Part D: Communicate

• Prepare an information folder for the RMS Gargantuan task force. The report should summarize the results of your research in an organized and concise manner. Your report should include the following components: the results of your research, including:
• a discussion of the oceanic conditions under which the Gargantuan was found
• a survey of shipbuilding materials and techniques for preventing corrosion in shipbuilding
• a discussion of the chemistry of the ocean environment
• a description of chemical methods used to analyze, restore, and conserve recovered
• your complete laboratory report
• a set of proposals for the task force, based on your research and investigation, describing how redox chemistry may be used in the conservation and restoration of the Gargantuan and artifacts from the Gargantuan

all references listed in APA style

Prepare a short presentation in which your group presents the procedure, results, conclusion, and discussion of your laboratory experiment. Your presentation should include a discussion of redox chemistry as it relates to your investigation. You should clearly demonstrate how your experiment contributes to the overall understanding of corrosion as it relates to ships in marine environments.