Problem 95 - Chemistry Matter and Change

Question

Statue of Liberty Several years ago, the supporting structure of the Statue of Liberty became so corroded that it had to be replaced entirely. Find out what the structure was made of and why it corroded so badly. Write a report that explains the chemical processes involved and include a time line of the statue, starting in France before 1886.

Step-by-Step Solution

Answer

The Statue of Liberty's original supporting structure was made of iron and was corroded due to galvanic corrosion. The chemical reaction occurred because of dissimilar metals (iron and copper) in contact with each other in a humid and salty environment, creating an electrolytic reaction that accelerated the corrosion process. Additionally, pollution contributed to the Statue's deterioration. Key events in the timeline include the statue's design and construction in France (1875-1884), its assembly in New York (1886), and the significant corrosion being noticed, leading to the replacement of the support structure in 1984. Understanding the corrosion process is essential for preserving historical monuments and preventing future damage.

Step 1: Research the supporting structure of the Statue of Liberty

Begin by researching the original materials used in the construction of the Statue of Liberty's supporting structure. Find out what the structure was made of, as well as any other involved materials that may have contributed to the corrosion. Use reliable sources such as historical archives, articles, and academic publications to gather information.

Step 2: Understand the corrosion process

Study the chemical reactions (either galvanic or other types of corrosion) that led to the deterioration of the supporting structure. For example, look into the effect of environmental factors like saltwater, humidity, and pollution on the materials used. Determine which factors played a significant role in the corrosion of the structure and explain the chemical processes in detail.

Step 3: Create a timeline

Develop a chronological overview of the Statue of Liberty, starting in France before 1886. Include key events such as when it was designed and constructed, transported to the United States, assembled and dedicated, and any refurbishments or replacements of the corroded supporting structure. Ensure that you include the year that the significant corrosion was noticed and the decision to replace the structure was made.

Step 4: Draft your report

Draft a well-organized report that outlines your findings. Be sure to include an introduction that briefly describes the issue and the purpose of your study. In the body of the report, explain the materials and their properties, the factors that contributed to the corrosion of the supporting structure, and the chemical reactions involved. Provide a detailed timeline of the Statue of Liberty with a focus on the corrosion issue. Conclude your report by summarizing your findings and discussing the importance of understanding the corrosion process for preservation purposes.

Step 5: Edit and proofread your report

Review your draft and make any necessary revisions to ensure your report is clear, concise, and well-organized. Check for spelling, grammar, and punctuation errors. Make sure that all sources of information are properly cited and that the report adheres to any required formatting guidelines.

Key Concepts

Corrosion processes

Corrosion is a natural process that occurs when metals are exposed to environmental elements over time, leading to their deterioration. It's like metal's version of rusting. In the case of the Statue of Liberty, the supporting structure originally made of iron suffered significant corrosion. Iron is prone to react with oxygen and moisture, forming iron oxide, commonly known as rust.
This process can be expedited by the presence of certain catalysts such as salt from the surrounding seawater and pollution in the air, which increase the conductivity of the environment, facilitating more aggressive corrosion. Understanding these processes helps to identify the causes of deterioration in historical structures and guides efforts in preservation.

Chemical reactions

Several types of chemical reactions can lead to corrosion, with galvanic and atmospheric corrosion being prevalent.
Galvanic corrosion occurs when two dissimilar metals are in electrical contact in the presence of an electrolyte, commonly moisture or saltwater.
Atmospheric corrosion results primarily from moisture and pollutants in the air.
When iron is exposed to constant contact with both moisture and oxygen, a redox reaction occurs, resulting in rust. This reaction can be represented by the equation:

• 4Fe + 3O₂ + 6H₂O → 4Fe(OH)₃

This equation demonstrates iron combining with oxygen and water to form iron hydroxide, which further oxidizes to form the red-brown rust. These chemical reactions were central to the corrosion problems experienced by the Statue of Liberty's iron framework.

Statue of Liberty timeline

The history of the Statue of Liberty began in the 19th century in France, where it was designed by sculptor Frédéric Auguste Bartholdi and built by Gustave Eiffel.
Assembling began in 1884 and it was completed and unveiled in France.
The statue was shipped to the United States in 1885 and dedicated on October 28, 1886. Fast forward to the latter half of the 20th century, significant corrosion of the supporting iron structure was detected.
Restoration efforts were commissioned in the 1980s, during which the original iron elements were replaced with stainless steel to prevent future corrosion. Understanding this timeline highlights the importance of maintenance and modernization efforts in preserving historic monuments.

Material properties

Different materials have distinct characteristics that affect their durability and susceptibility to corrosion.
The Statue of Liberty's original support was made of iron, a strong but corrosion-prone metal, especially in the harsh marine environment surrounding Liberty Island.
Iron inherently reacts with air and moisture, its properties making it susceptible to oxidization, more so in the presence of salt and pollutants.
The statue's outer shell, however, is composed of copper, which, though also reactive, forms a protective patina over time that safeguards the underlying metal from further corrosion.
Recognizing these material properties guides the selection of materials in restoration and preservation efforts to ensure long-term sustainability.

Preservation methods

Several methods can be employed for preserving historical structures like the Statue of Liberty. Selecting materials resistant to environmental factors is paramount.
For the Statue, replacing iron with stainless steel was a critical step in updating its supporting structure.

• Stainless steel is an alloy with chromium, which forms a passive layer of chromium oxide that protects against further corrosion.
• Additionally, regular maintenance, protective coatings, and environmental monitoring systems help detect and mitigate corrosive elements.
• Implementing such preservation interventions ensures the longevity of heritage sites by addressing proactive maintenance needs and adapting to technological advancements.

This approach not only preserves the structural integrity but also ensures the cultural and historical significance endures.