ABSTRACT

Although all metals are able to corrode, the time it takes for it to corrode and in what condition each metal corrodes best varies among the different types of metals. The objective of this experiment was to determine how different temperatures of the solution of water and TSP would affect the time and amount of corrosion of the magnesium metal. 4 drastically different temperatures (-18°C, 4°C, 25°C, 37°C) were chosen in order to carry out the experiment successfully. Each piece of metal was placed into a solution of 100mL tap water and 10g TSP. After 6 days, the metal was taken out of the solution, and its mass was measured in order to see how much it had corroded. The experiment was done for 4 trials, and the data showed that although the metals had corroded, there was not much difference in how much the metal had corroded among the different temperatures. These results suggest that magnesium metal does best corrode in warmer and polluted environments. Further research such as trying the metal corrosion experiment by using a substance that would help pollute the environment even more than TSP would help to figure out a more accurate relationship of how different temperatures affect the corrosion of metals, especially the magnesium metal, since it would show a more dramatic effect.

INTRODUCTION

Background Information:

Corrosion is when a refined metal is naturally converted to a more stable form such as its oxide, hydroxide or sulphide state that leads to deterioration of the material. (1) Although all metals corrode, some metals acquire a natural passivity, or resistance to corrosion. This occurs when the metal reacts with, or corrodes in, the oxygen in air. (2) Corrosion has several harmful effects such as plant shutdowns, waste of valuable resources, loss or contamination of product, reduction in efficiency, costly maintenance. (3) Although each metal varies on how quickly and in what environment it best corrodes, a study has found that metals corroded at a much faster rate in warmer temperatures (4), and when pollution levels were at their highest (5).

Hypothesis & Goal:

The goal of this experiment was to determine how different temperatures would affect the corrosion of metal that is in a polluted environment. If it is true that temperature affects the amount it takes for a metal to corrode, then I expect that the mass of the metal in the incubator will decrease the most after a certain period of time.

MATERIALS & METHODS

Before starting any step of the experiment, magnesium metal was chosen to be used in this experiment because Mr. Tyler informed me that magnesium metal would corrode most quickly out of the metals that I would be able to use. First, the long strand of metal was cut evenly so that each metal piece weighed 0.64g. (A measuring device was used to measure the precise mass of each metal piece) Once the metal was prepared, 4 bottles of 250mL bottles were prepared in order to make the mixture of water and TSP. 100mL of tap water was mixed with 10g of TSP in each bottle. A stirring stick was used in order to make sure that the TSP was spread out in the water solution. During preliminary testing, several experiments were tried out in order to figure out what would be the inappropriate amount of tap water and TSP. At first, 200mL of water with 5g of TSP, 200mL of water with 10g TSP, 100mL of water with 5g of TSP, and 100mL water with 10g of TSP were conducted as preliminary testing. However, it was concluded that 100mL of water with 10g TSP showed the most difference in mass of the magnesium metal, so this choice was chosen for the actual experiment. The other choices had too much water compared to the amount of TSP. TSP was mixed with water because it has been proven that magnesium metal best corrodes in a cold and polluted condition. Afterwards, each of the metal pieces, which were bent into circular shapes to make them fit in the bottle, were put into the bottle and was made sure that the metal was completely soaked in the mixture. Then the 4 bottles were each placed in different temperatures; one was put in the freezer (-18°C), another in the fridge (4°C), the third in the chemistry classroom to remain room temperature(25°C), and the last one inside the incubator (37°C). 4 most different possible combinations were chosen for the temperatures. Thus, there were 4 runs. Each temperature went through 4 trials. After 6 days, the metal was taken out of the solution in the bottle. The mass of the metal was then measured. (The metal piece was wiped in order to make sure that there was no solution on the metal which could increase the mass) The controlled variable for this experiment was the amount of water and TSP used to make the solution. When the amount of water was different, it was concluded that the amount of water has a direct relationship to how quickly the metal corrodes as the metal resists to corrode as there is more water. Moreover, the amount of TSP used was also a controlled variable because as the amount of TSP in the solution differed, the concentration of the pollution of the environment changed.

DISCUSSION

Outcome vs. Hypothesis:

My initial hypothesis when setting up the experiment was that metal would best corrode in a polluted and warmer environment. Throughout the experiment, because all 4 conditions were polluted, the warmer the temperature of the solution that the metal was in would cause a faster rate of corrosion, thus the greatest difference between the initial and final mass of the metal. The outcome of the experiment did match my initial hypothesis. Although the difference in mass of the magnesium metal between the warmest temperature and coldest temperature did not have much difference, the results showed that the warmest temperature allowed the fastest corrosion rate of the metal.

Data Interpretation:

As can be seen from the T-test values, all three of the values were less than 0.05, thus the sets of data were significantly different. The average magnesium metal that corroded in the freezer was compared with the average magnesium metal that corroded in the refrigerator. The average magnesium metal that corroded in the refrigerator was compared with the average magnesium metal that corroded in the room temperature. The average magnesium metal that corroded in room temperature was compared with the average magnesium metal that corroded in the incubator.

From the results, it is seen that magnesium metal most quickly corrodes in the highest temperature. When a temperature is increased, it would lead to a higher corrosion rate because electrochemical reactions inside the metal occur more quickly at higher temperatures. Moreover, metals generally tend to oxidize when they are exposed to oxygen. So, the chemical reaction of the metal surface with the oxygen present causes the metal to corrode and forms respective metal oxide on the surface. (6) At higher temperatures, because the oxidation process becomes faster, it adds energy to the chemical reactions happening, thus causing the corrosion rate to increase. (5)

Sources of Uncertainty:

A source of uncertainty throughout the experiment that could have affected the results is the final mass of the magnesium metal. Because the metal had been sitting in the solution for several days, the solution might have gotten attached to the metal, which may have had an effect on why there was not much difference in change of mass. In order to reduce this source of uncertainty, I could make sure to wipe the metal with alcohol in order to make sure that all of the solution has been detached from the metal. Paper towel with water could also be used, but that might not effectively reduce all of the solution on the metal.

Further Study:

An experiment for further study should be this same experiment carried out for a longer time. Metal takes a very long time to corrode even in the best condition for corrosion. By conducting this experiment for a longer period of time, the results in the difference of mass will be more clear among the different temperatures.

CONCLUSION

Although the 4 different temperatures did not show much difference in change of the mass of the magnesium metal, the results of this experiment show that metal best corrodes in warmer temperatures and in polluted environments.

SOURCES

(1) TWI, "What is Corrosion? - Definition and Prevention" https://www.twi-global.com/technical-knowledge/faqs/what-is-corrosion

(2) The Electrochemical Society, "Corrosion and Corrosion Prevention" https://www.electrochem.org/corrosion-science/

(3) Researchgate, "What are the Harmful Effects of Corrosion?" June 2014 https://www.researchgate.net/publication/265178626_What_are_the_harmful_effects_of_corrosion

(4) GateKeeper - A Technical Newsletter for the Oil and Gas Industry "Corrosion Modeling: Influencing Factors" February 2014 http://static1.squarespace.com/static/53556018e4b0fe1121e112e6/54b683d0e4b09b2abd348a7b/54b683e3e4b09b2abd348e64/1421247459525/GAT2004-2014-02-Final-Corrosion-Modeling-Influencing-Factors-LDAwbleed-LTD.pdf?format=original

(5) Camfil "What are the Effects of Corrosion?" https://cleanair.camfil.us/2017/08/22/the-effects-of-corrosion/

(6) Advanced Plating Technologies "What Causes Metal to Oxidize or 'Rust'?" https://advancedplatingtech.com/technical-library/plating-topics/causes-metals-oxidize-rust/