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These three companies offer solutions to the rust problem, but they can also work as a preventative measure. Sometimes the corrosion has seeped in so deep that it is difficult to repair, and replacements are done.
Morandi Bridge
Italy, 2018
Casualties - 43
Cables in the steel bridge stays corroded.
In this lesson we will look at why some items corrode easier than others and how to prevent the problem from occurring.
Why do some parts of a car rust, while others do not? It depends on how the metal has been protected.
Painting
When body shops paint a vehicle, they are in an environmentally controlled room. This is to prevent the application of painting the metal from having any impurities and moisture. Painting the metal on the car prevents oxygen and water from reaching the surface of the metal. If you look at the steel beams used in buildings, you will see that it has been painted red. This red-oxide primer is put on the steel before it is shipped. It is a short-term finish that protects the steel from moisture.
Salt water corrodes metal five time faster than fresh water. Combine this with the high humidity the metals located near these locations corrode 10 times faster.
Ship Graveyard - Musquash, New Brunswick
Once the paint on these ships chipped off, water and oxygen were able to get to the metal more easily causing the rust to blister quite quickly.
Galvanizing
Galvanizing is another way to protect steel and iron. Galvanization is the process of applying zinc by immersing the metal into a bath of molten zinc. This process allows the base metal to be protected and resist chipping and cracking because the zinc actually becomes part of the surface of the steel.
As we learned in Chapter 1, polymers are substances that contain large molecules of repeating chains which allow for it to be molded and shaped.
Some galvanized nails have a double protection. After being galvanized, they are coated with a polymer to provide greater protection.
Sacrificial Metal
Buried with many steel pipes will be a bar of metal that is made of magnesium. The magnesium will rust, but the steel pipe will not. This is why the name of this type of protection is called sacrificial metal. It is easier and cheaper to replace the magnesium bar to protect the pipeline.
Equation for Sacrificial Metal
2Mg(s) + O2(g) →2MgO(s)
Magnesium + Oxygen → Magnesium oxide
Check Your Understanding
Explain why the chemical reaction for the rusting of steel is similar to the chemical reaction for the combustion of fossil fuel.
How does painting a steel beam protect it from rusting?
How does dipping nails in molten zinc prevent them from corroding?
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