Zinc is categorized as a non-ferrous metal. Metal classification is based on elemental composition, specifically the presence or absence of iron. Zinc (chemical symbol Zn, atomic number 30) does not contain iron as a primary component. This distinction is key to recognizing why zinc possesses specific properties valuable for various industrial applications.
Defining Ferrous and Non-Ferrous Metals
The primary difference between these two major metal groups is the presence of iron, derived from the Latin word ferrum. Ferrous metals, such as carbon steel, alloy steel, and cast iron, contain iron as their main constituent. This elemental inclusion gives them certain shared characteristics, including high tensile strength and durability, making them the most widely used group of metals globally.
A significant consequence of containing iron is that ferrous metals are typically magnetic and highly susceptible to rust and corrosion when exposed to moisture and oxygen. Exceptions, like stainless steel, achieve corrosion resistance through the addition of other elements, such as chromium. However, the iron content remains the defining factor for the ferrous classification.
Non-ferrous metals are defined as metals or alloys that do not contain iron in significant amounts. This category includes pure metals like zinc, copper, aluminum, and precious metals. Because they lack iron, non-ferrous metals generally possess a much higher natural resistance to corrosion and rust.
These metals also tend to be lighter in weight, more malleable, and do not exhibit ferromagnetic properties, meaning they are non-magnetic. While non-ferrous metals are often more costly than ferrous metals, their unique blend of properties, including good electrical and thermal conductivity, makes them indispensable for specialized applications.
Why Zinc is Classified as Non-Ferrous
Zinc (Zn) is classified as a non-ferrous metal because it is a standalone element that contains zero iron atoms. Its inherent properties align perfectly with the non-ferrous category. Zinc is notably resistant to corrosion in ordinary atmospheric conditions because it forms a thin, tough, and impervious coating of zinc oxide or zinc carbonate on its surface when exposed to air.
This protective layer acts as a self-healing barrier, preventing the underlying metal from further degradation. Zinc also possesses a relatively low melting point, approximately 420 degrees Celsius (787 degrees Fahrenheit), which makes it suitable for processes like die-casting. This contrasts with the higher melting points characteristic of most ferrous metals.
The lack of iron means that zinc is diamagnetic, a property where the material is slightly repelled by a magnetic field. When zinc is alloyed with other non-ferrous metals, such as copper to create brass, the resulting material retains the non-ferrous classification. The elemental composition dictates its behavior, distinguishing it from the iron-containing ferrous group.
Common Industrial Uses of Zinc
The corrosion resistance of zinc makes it primarily utilized in the process known as galvanizing. About half of the world’s zinc production is dedicated to applying a protective zinc coating to iron and steel to prevent rusting. This coating works through sacrificial protection, preferentially corroding before the protected steel underneath.
Zinc is also a critical component in the creation of many useful alloys. When combined with copper, it forms brass, an alloy valued for its acoustic properties, strength, and resistance to corrosion, used in musical instruments, plumbing, and hardware.
Additionally, zinc is used in the manufacturing of die-cast parts for the automotive industry due to its excellent casting ability and moderate strength.
Zinc is a component in a variety of batteries, such as zinc-carbon and alkaline types, where it functions as the anode. Beyond its metallic applications, zinc compounds are used in products ranging from sunscreen and anti-dandruff shampoos to rubber manufacturing and agricultural applications. The metal’s versatility makes it the fourth most-produced metal globally, exceeded only by iron, aluminum, and copper.