Why are most engineering metals used as alloys rather than in their pure form?

Pure metals are too expensive to extract from ore Alloying allows engineers to tailor properties such as strength, hardness, and corrosion resistance that pure metals cannot achieve alone Pure metals are always radioactive and unsafe Alloying reduces the density of metals to make them float

How does increasing carbon content affect the properties of steel?

Strength decreases and corrosion resistance increases Hardness and strength increase, but ductility decreases Density decreases and thermal conductivity increases Melting point decreases significantly

Stainless steel resists rust primarily because it contains:

Large amounts of nickel, which repels water molecules At least 10.5% chromium, which forms a self-repairing oxide layer on the surface A wax coating applied during manufacture High carbon content that seals pores in the surface

Aluminium is widely used in aircraft construction mainly because:

It is magnetic, which helps navigation instruments It is cheaper than all other structural materials It has a good strength-to-weight ratio, is corrosion-resistant, and is a good electrical conductor It becomes stronger at cryogenic temperatures

Titanium is used in aircraft components and surgical implants primarily because it:

Is the cheapest metal available in large quantities Has an extremely high strength-to-weight ratio and is biocompatible Is highly magnetic and can be guided by external magnets Melts at room temperature, making it easy to cast

Copper is the preferred material for household electrical wiring because it:

Is the lightest metal and reduces cable weight Is non-metallic and therefore safe to touch Has very high electrical conductivity and is sufficiently ductile to be drawn into fine wire Has the highest melting point of any metal

Brass is an alloy of copper and which other element?

Tin Aluminium Zinc Nickel

Galvanising a steel structure involves coating it with a thin layer of zinc. How does this prevent corrosion?

Zinc forms a perfectly waterproof seal that no moisture can penetrate Zinc is inert and completely resists all chemical reactions Zinc corrodes preferentially (sacrificial anode), protecting the steel even if the coating is scratched Zinc increases the melting point of steel so it cannot rust at normal temperatures

Galvanic corrosion occurs when:

A single metal is exposed to very high temperatures in a furnace Two different metals are in electrical contact in the presence of an electrolyte, causing the less noble metal to corrode faster A metal is painted with an alkaline coating that reacts with its surface An alloy separates back into its component pure metals over time

Cathodic protection is used to protect buried pipelines and ship hulls from corrosion. It works by:

Coating the surface with a thick layer of grease to block oxygen Heating the metal to drive off all moisture Making the structure the cathode of an electrochemical cell so it cannot corrode Alloying the metal with a corrosion-resistant element after installation

Bronze, used for gears and bearings, is an alloy of copper and:

Zinc Tin Lead Silver

Mild steel (low-carbon steel) is preferred over high-carbon steel for fabricating structural beams and car body panels because it is:

Stronger and harder, giving better structural performance More ductile and easier to weld, form, and shape Lighter than all other steel grades Completely immune to corrosion without any treatment