The Basics of Electricity
The term “electricity” comes from the Greek word for “amber,” referencing how the ancient Greeks discovered that rubbing amber with fur would attract small objects. This phenomenon is due to the fundamental structure of matter and the behavior of tiny particles called atoms. Atoms are the building blocks of everything around us, and are composed of even smaller particles: a nucleus containing positively charged protons, and negatively charged electrons that orbit around it.
The interaction of these charged particles creates the concept of electricity. Electrons are not static, they are always moving. When these electrons move between atoms, it creates an electric current. The concentration of electrons in a single place is known as electrical potential, which we measure in volts. This potential is what makes the flow of electricity possible and how we are able to control it for a variety of applications.
The Electrochemical Series
Different materials have their own electrical charge. When these charges are listed in order we get the electrochemical series. This list shows how active or stable a metal is based on its electrical potential. Metals higher in the list are more negatively charged and therefore more active, while metals lower in the list are more stable and positive, also known as noble metals. This is very important in the construction business, as this means that when two different metals are in contact, electrons will flow from the more active metal to the less active one.
How Electricity Causes Corrosion
The movement of electrons is not always good, as it can cause corrosion. When electrons flow out of a metal, the metal reacts with oxygen, which causes it to corrode, or in the case of iron and steel, to rust. This means that if different metals are used together in a plumbing or construction system, the more active metal will corrode faster than the more stable one. For example, if you connect a copper pipe to a steel pipe, the steel pipe will rust very quickly.
Preventing Corrosion in Construction
While we can’t stop the flow of electricity between metals, we can utilize that process to our advantage. There are several ways of doing this, most of them involving the use of more active metals to protect less active and more important structural components.
- Sacrificial Anodes: We can attach a more active metal, such as aluminum or magnesium, to a piece of steel. In seawater, the aluminum will corrode instead of the steel, effectively providing “cathodic protection”. This is why sacrificial anodes are commonly used in water heaters to protect the steel tanks.
- Painting: Painting steel creates an insulating layer that blocks the interaction between steel, oxygen, and water and prevents corrosion. Adding zinc or lead to the paint further enhances its protective qualities.
- Hot-Dip Galvanizing: This method involves dipping the steel into molten zinc, which forms a layer of zinc that will corrode before the steel.
- Zinc Alume: A mix of aluminum and zinc that is used to coat corrugated iron, it protects the steel even if it is scratched.
- Anodizing: Some metals, like aluminum, can be protected by corroding their surface intentionally. This forms a thick crust on the surface which protects the aluminum underneath.
Conclusion
Understanding the principles of electricity and its effect on metal is crucial in the construction business. By taking steps to protect metals used in construction, we can increase the longevity and durability of the structures we build. It’s important to take these points into consideration when planning, and when selecting materials and construction methods.
