Bridge Cable Corrosion

Elisabeth Castelli

Manhattan East Middle School

Summer Research Program for Science Teachers

August 2008




            Students will be introduced to the processes and chemistry of corrosion through a lab and classroom activity looking at suspension bridges. Students will attempt bridge construction in the classroom using wood sticks to assess bridge load capabilities. Then optimization will be discussed using the knowledge of corrosion and environment along with bridge construction to determine the best materials for construction in a group scenario.

Background Knowledge

A basic knowledge or quick review of comparative reactivity of metals on the periodic table will be helpful. Also, an understanding of acid base chemistry and how phenolphthalein indicator can be used to determine pH will prove useful. 


1. What is Corrosion?

 - Corrosion in Bridges PowerPoint

 - Guided Notes Handout

 - Corrosion in Metals Lab

2. Bridge Construction and Load Capacity

           - Bridge Construction Lab

- Bridge Blueprint Worksheet

- Reading Assignment: "Steel-reinforced Concrete Bridge Decks" 


3. Assessment

          - Bridge Optimization Group Project


 Lesson Outline –What is Corrosion?

Do Now – Student each receive a copy of the guided notes as they walk in and are asked to fill out the very first blank on the page.

Mini Lesson – The teacher goes through the Corrosion in Bridges PowerPoint with the students as they keep up with their copy of the guided notes, making sure to fill in any blanks and answer any questions.

Lab Activity - Students will choose a partner for this lab activity. Each student needs a copy of the Corrosion Lab. One student is responsible for gathering the solid material and the other will be responsible for gathering the liquid materials. The Corrosion lab is then performed, making sure that students take accurate observations on both day 1 and day 2. Below are the observations that should be seen by the students.



Experimental Conditions



Day 1

Dish 1



(+ phenolphthalein + potassium ferricyanide)

Unprotected iron: light pink cloud starts to form around iron. The iron surface itself appears darker blue.

Unprotected iron

Dish 2 zinc

Iron wrapped with zinc

(+ phenolphthalein + potassium ferricyanide)

Wrapped iron: Light pink cloud to form. No darker blue on iron.

Wrapped iron

Dish 2 copper

Iron wrapped with copper

(+ phenolphthalein + potassium ferricyanide)

Wrapped iron: Light pink cloud starts to form. Slightly darker blue color appears on iron surface.

Wrapped iron

Day 2

Dish 1



(+ phenolphthalein + potassium ferricyanide)

Unprotected iron: A larger, darker pink cloud surrounds the metal strip. A dark blue color is also forming close to the strip in patches.

Unprotected iron

Dish 2 zinc

Iron wrapped with zinc

(+ phenolphthalein + potassium ferricyanide)

Protected iron: A larger, darker pink cloud is present and a white solid surrounds the zinc. The iron is still metallic gray.

Protected iron

Dish 2 copper

Iron wrapped with copper

(+ phenolphthalein + potassium ferricyanide)

Protected iron: A darker pink cloud surrounds the iron strip. The iron strip is darker blue in patches.

Protected iron














Homework – Students will complete the discussion questions from the corrosion lab.


 Lesson Outline –Bridge Construction and Load Capacity

Do Now – Students receive a piece of paper and fold it in half.  On the first side they draw two bridges that either exist or could exist (looks structurally sound).

 Mini Lesson – Students choose one partner to work with and share their two bridge sketches. They then receive a copy of the Bridge Construction Lab and read through the directions. Make sure to go over the instructions that way students have an idea of what they are designing their bridges for.  Then hand students a copy of the Bridge Blueprint Worksheet and do one example of a bridge side on the board.

 Lab Activity - Students will choose a partner for this lab activity as well. Each group will need a pencil and a ruler to create their bridge side and should get their design approved by the teacher before continuing on to the gluing of the coffee stirrers to each other and pinning them down to the Styrofoam with the design on it. Bridge sides will need to dry for 24 hours and then the connecting coffee stirrers will need to dry for an additional 24 hours. When this is finished, students will weigh their bridges and then use textbooks to figure out the maximum load capacity. Students should calculate optimization and finish the two lab questions in class.

 Homework – Students will complete reading assignment, “Steel-reinforced Concrete Bridge Decks."


Lesson Outline –Bridge Optimization

Do Now – Student each receive a copy of the Bridge Optimization Scenario and are asked to get into groups of 3 people, while taking out their reading assignments from the night before (to be used for reference material).

Mini Lesson – Students are asked to read the problem section of the optimization scenario and then discuss it together in their groups for 10 minutes. Then, as a class the teacher should go over the two tables and discuss their contents and they can be interpreted with the class.

Group Activity – Students will then complete the assessment in groups with the idea that each student will be responsible for turning in a paper on one of the bridges (3 three students per group, for a total of 3 bridges: #1-3).

Homework – Students will complete their respective bridge papers, that were self assigned within their groups.


New York State Standards 


Standard 1: Analysis, Inquiry, and Design

  Engineering Design: Engineering design is an iterative process involving modeling and  

   optimization (finding the best solution within given constraints); this process is used to  

   develop technological solutions to problems within given constraints. 

Standard 4: Concepts, Principles, and Theories

    Key Idea 2: Many of the phenomena that we observe on Earth involve interactions   

     among components of air, water, and land.

2.1s --Weathering is the physical and chemical breakdown of rocks at or near Earth’s surface. Soils are the result of weathering and biological activity over long periods of time.

     Key Idea 3: Matter is made up of particles whose properties determine the observable characteristics of matter and its reactivity.

3.1a --Minerals have physical properties determined by their chemical composition and crystal structure. Chemical composition and physical properties determine how minerals are used by humans.

Standard 6: Interconnectedness, Common Themes

   Models: Models are simplified representations of objects, structures, or systems used in analysis, explanation, interpretation, or design.

   Optimization: In order to arrive at the best solution that meets criteria within constraints, it is often necessary to make trade-offs.

 Standard 7: Interdisciplinary Problem Solving

    Connections: The knowledge and skills of mathematics, science, and technology are  

    used together to make informed decisions and solve problems, especially those relating

    to issues of science/technology/society, consumer decision making, design, and inquiry        

    into phenomena.

    Problem Solving: Solving interdisciplinary problems involves a variety of skills and   

    strategies, including effective work habits; gathering and processing information;

    generating and analyzing ideas; realizing ideas; making connections among the

    common themes of mathematics, science, and technology; and presenting results.



Corrosion Lab and Bridge Optimization Activity adapted from NSTA Science Teacher article “Corrosion in the Classroom” written by: Gary S. Drigel, Arlyne M. Sarquis, and Mike D’Agostino. (April/May 2008, Vol. 75, No.4, pgs. 50-56)