The Corrosion of Steel in Different Solutions Fair Report... · The Corrosion of Steel in Different...

The Corrosion of Steel in Different

Solutions

1104

The Corrosion of Steel in Different Everyday Solutions 1104 Page 1

Table of Contents

Project abstract …........................................................................................ pg. 2

Question/Problem & Hypothesis……………………………………………….. pg. 2

Background Research …………………………………………………………... pg. 3

Experiment Materials…………………………………………………………….. pg. 6

Experiment Procedures………………………………………………………….. pg. 7

Experiment Variables ……………………………………………………………. pg. 8

Data Table………….. ……………………………………………………………. pg. 9

Analysis Graphs/Charts………………………………………………………….. pg. 11

Analysis………. …………….…………………………………………………….. pg. 11

Conclusion…………. …………………………………………………………….. pg. 13

Biblical Principle ………………………………………………………………….. pg. 14

Bibliography………………………………………………………………………...pg. 14


ABSTRACT

Objective/Goals: This project is designed to determine if steel corrodes at a faster rate

in solutions with more acidic pH. This will be measured by the weight loss of a piece of

steel that is submerged in solutions of different pH over twenty-five days.

Methods/Materials: This experiment will use five different solutions; Coca Cola, coffee,

vinegar, water and Windex and will have a piece of steel immersed in each solution.

Each day that the experiment is running, the steel will be removed and weighed. The

weight loss is an indication of how much corrosion has occurred.

Results: As expected, it was found that the steel weight loss was greater and faster in

solutions with lower, more acidic pH’s than those approaching neutral or alkaline.

Conclusion: in conclusion, this experiment has developed support for the hypothesis,

which predicted the rate of corrosion, and so weight loss to increase when the steel was

immersed in solutions with more acidic pH.

Question and Hypothesis:

Is the corrosion of steel affected by the solution it is in?

If the pH of the solution that the steel is in becomes more acidic, then I predict

the rate of corrosion will increase.


BACKGROUND RESEARCH:

This experiment will examine if the corrosion of steel is affected by the solution it

is exposed to. The solutions that will be tested are items people use in their day-to-day

lives such as Coca Cola, coffee, vinegar, and water. Corrosion is caused by chemical

reactions between metal, in this experiment iron, with the solution around it. It has two

parts in the reaction, the oxidation reaction and the reduction reaction. When corrosion

occurs the properties of the metal are lost, and a corrosion product is formed. In this

study, the properties of steel are lost and the corrosion product, called iron oxide, is

formed. Iron oxide is one of the most common corrosion products that we see everyday

and is most commonly known as rust.

In order for corrosion to happen there needs to be certain conditions. The

corrosion cell must have an anode, a cathode and a solution to allow the chemical

reactions to take place. A corrosion cell can occur when there are two different metals in

contact in a corrosive solution. Also, the anode and cathode can sometimes exist on the

same piece of. For example, a scratch on a piece of metal e.g. steel, can cause a

corrosion cell to form, the shiny metal being the anode and the other surface being the

cathode. This can happen with steel and it corrodes to form rust as shown in the

diagram below.


In the corrosion cell, the oxidation reaction releases electrons, which are

negatively charged, and the reduction reaction requires electrons to enable the reaction

to occur. The two-reactions combine to produce iron oxide, more commonly known as

rust.

Oxidation Reaction occurs at the Anode:

Fe(s) Fe2+(aq) + 2e-

Reduction Reaction occurs at the Cathode:

2H2O(|) + O2(g) + 4e- 4OH-(aq)

Overall Reaction:

2Fe(s) + 2H2O(I) + O2(g) 2Fe(OH)2(s)

Corrosion of metals can be affected by what solution surrounding the metal.

Steel corrodes faster in acidic solutions than it does in neutral solutions. The level of

acidity in a solution is measured by pH. In chemistry, pH is the measure of

concentration of hydrogen ions in a solution. The pH equation is:

pH = -log10[H+]


The pH measures the concentration of hydrogen ions in a solution of water. The

pH scales measures the solution from 0 to 14. If the solution is more than 8 the pH the

solution is alkaline. When a solution is between 0 and 6 the solution is acidic, and if it is

between 6 and 8 the solution is neutral. Basic and acidic are two extremes that describe

chemicals. When you mix both acids and bases solutions together it cancels out the

extreme affect and it may produce a neutral solution. Below is a schematic of the pH

range that indicates low pH numbers are acidic and high pH numbers are alkaline.


EXPERIMENT:

Materials List:

• A pH meter

• Scales to measure the weight of the test coupon

• A digital camera to take photographs

• Mild Steel samples cut into 2” x 2” coupons. (Four coupons per test environment)

• Plastic cups for the test solution and test coupons

• Test solutions:

o Coca Cola

o Coffee

o Vinegar

o Water

Steel Test Coupon

Scales


Procedures:

1. Cut steel the thin gage sheet into sixteen 2” x 2” test coupons.

2. Each of the steel coupons will be weighed. The steel test coupon was marked with a

sharpie pen with a number 1-16

3. Prepare four test coupons for each test environment.

4. Fill four plastic drink cups with each of the four test environments. There were 16 cups in

all with four different test solutions.

5. The pH of each test solution was measured at the beginning of the experiment.

6. Each test coupon will have a number written onto it with a Sharpie pen.

7. Test coupons were placed in the test environments:

a) 1-4 in Coca Cola

b) 5-8 in Vinegar

c) 9-12 in Black Coffee

d) 13-16 in Tap water

8. The test will run for 16 days.

9. Each day the steel coupon was removed from the test environment and dried with a

paper towel. The time the steel coupon will be removed from the solution then noted and

weighed. The weight of the steel coupon was recorded.

10. The daily measurement of the steel coupon weight was repeated daily for 16 days.

11. At the end of the experiment, the four samples from each test solution were lined up on

a paper towel and a photograph was taken.


Variables:

1) DEPENDENT VARIABLES

• Weight of steel coupon during the test

2) INDEPENDENT VARIABLES

• Time between measurements

3) CONSTANTS

• pH of the test environment

Test Coupons at the End of the Experiment


DATA COLLECTION:

Each day the test coupon in each test solution was removed, dried and weighed

to measure the weight loss per day. The data was recorded for each of the samples in

each of the test solutions and it was entered into an excel data table. Each data table,

for each of the test samples was glued into the project notebook. Once all four sets of

data were recorded for each of the four test solutions, a summary data table was

prepared which recorded the weight loss per test coupon per day. An average weight

loss for each test solution was calculated:

Average Daily Weight Loss = Sample 1 + Sample 2 + Sample 3 + Sample 4

4

The average daily weight loss for each test solution is shown in Table 1. The

summary of these data are shown in Chart 1 that shows the average daily weight loss

per test solution between December 19th 2013 and January 3rd 2014.


Table 1 Average Daily Weight Loss

Date Coca Cola

(g) Vinegar

(g) Black Coffee

(g) Water (g)

19‐Dec‐13 0.43 0.29 0.13 0.00 20‐Dec‐13 0.37 0.23 0.05 0.00 21‐Dec‐13 0.42 0.30 0.15 0.00 22‐Dec‐13 0.37 0.23 0.03 0.00 23‐Dec‐13 0.45 0.33 0.16 0.00 24‐Dec‐13 0.31 0.17 0.06 0.00 25‐Dec‐13 0.37 0.27 0.12 0.00 26‐Dec‐13 0.41 0.31 0.09 0.00 27‐Dec‐13 0.42 0.27 0.11 0.00 28‐Dec‐13 0.41 0.28 0.10 0.00 29‐Dec‐13 0.35 0.20 0.05 0.00 30‐Dec‐13 0.47 0.31 0.14 0.00 31‐Dec‐13 0.38 0.23 0.06 0.00 1‐Jan‐14 0.42 0.27 0.16 0.00 2‐Jan‐14 0.36 0.23 0.15 0.00

3‐Jan‐14 0.36 0.21 0.04 0.00


ANALYSIS:

It was expected from the background research that steel would corrode in acidic

solutions. The method for measuring how much corrosion occurs with the test samples

was how much weight loss the steel experienced while immersed in the test solutions.

At the start of the experiment, the pH of the test solutions was measured using a pH

meter and found the solutions had the following pH:

Test Solution pH of Test Solution

Coca Cola 2.8

Vinegar 3.0

Black Coffee 5.3

Water 7.0

The background research states that steel corrodes more quickly in a solution

that is more acidic. So, based upon the pH of the test solutions at the start of the

experiment, it would be expected that the steel in Coca Cola corrodes slightly faster

than Vinegar which corrodes faster than Black Coffee. The research also states that

steel is passive in neutral environments, which means it does not corrode quickly.

Therefore in the short sixteen-day test period it would have been expected to see no

corrosion, or at the very most a small amount of corrosion, which would show as no

weight loss, or a very small amount of weight loss.

When looking at the data in terms of cumulative weight loss for each test

solution, you can most effectively see how quickly the steel is corroding. The data of

cumulative weight loss is plotted against the test dates shows lines with slopes of


different steepness. The steepest line shows that corrosion is fastest in that test

solution. The test data is represented in Table 2 and Chart 2 which shows the

cumulative weight loss data for each test solution.

Table 2 Average Cumulative Weight Loss

Date Coca Cola

(g) Vinegar

(g) Black Coffee

(g) Water (g)

19‐Dec‐13 0.43 0.29 0.13 0.00 20‐Dec‐13 0.80 0.52 0.18 0.00 21‐Dec‐13 1.22 0.82 0.33 0.00 22‐Dec‐13 1.59 1.05 0.36 0.00 23‐Dec‐13 2.03 1.37 0.51 0.00 24‐Dec‐13 2.34 1.54 0.57 0.00 25‐Dec‐13 2.71 1.81 0.69 0.00 26‐Dec‐13 3.12 2.12 0.78 0.00 27‐Dec‐13 3.53 2.39 0.89 0.00 28‐Dec‐13 3.94 2.67 0.99 0.00 29‐Dec‐13 4.28 2.86 1.03 0.00 30‐Dec‐13 4.75 3.18 1.17 0.00 31‐Dec‐13 5.12 3.40 1.23 0.00 1‐Jan‐14 5.54 3.67 1.39 0.00 2‐Jan‐14 5.89 3.90 1.53 0.00

3‐Jan‐14 6.25 4.11 1.57 0.00


CONCLUSION:

This experiment has clearly shown that steel will corrode at a faster rate when

immersed in a solution that is more acidic and has a lower pH. The rate of corrosion

was measured in terms of how much weight the steel sample lost from the start of the

experiment to the time that the experiment ended. As the acidity of a solution increases,

so the concentration of H+ ions also increases as:

pH = -log10[H+]

Therefore, as more hydrogen ions are available when solutions are more acidic,

it would be expected that the rate of corrosion of steel would increase the more acidic

the immersion solution is. In acidic solutions, iron reacts with the hydrogen ions to

produce iron ions and hydrogen gas:

Fe(s) + 2H+(aq) Fe2+(aq) + H2 (g)


In conclusion, the experimental data and the analysis support the hypothesis that

stated that the corrosion of steel would increase as the pH of the immersion solution

became more acidic.

BIBLICAL PRINCIPLE: “For the same way you judge others, you will be judged, and with the measure you use,

it will be measured to you.” ~Matthew 7:2

I chose this bible verse because it applied to this project in many ways. One way

it applied to this project was the measurement. During this project I had to measure the

steel as it was decaying and I had to mark down the size and weight. Another part that

is connected to this project is the judgment part. Many different teachers, adults and

scientists, are judging this science project. The bible verse Matthew 17:2 connects to

my science fair project about the corrosion of steel in different solutions.

Bibliography:

Bellama, Jon; Umland, Jean. General Chemistry: Third Edition. Albany: Brooks/Cole

Publishing Company, 1999. Print.

Jenner, Jen; Lisowski, Marylin; Wellneitz, Thomas; Cronin-Jones, Linda; Brook-

Simons, Barbra; Wysession, Michael. California Focus on Physical Science. Glenville,

IL: Pearson Inc., 2008. Print.

Russo, Steve; Silver, Mike. Introductory Chemistry: Second Editon. San Francisico:

Benjamin Cummings, 2002. Print.

Silberberg, Martin Stuart. Chemistry: The Molecular Nature of Matter and Change.

Boston: McGraw-Hill, 2003. Print.

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