Principles of Metallurgy and Corrosion

Comprehensive vocabulary flashcards reviewing key terms, definitions, chemical formulas, and processes from the lecture notes on metallurgy, furnaces, and corrosion.

Mineral

Naturally occurring elements or compounds of metals found in the Earth's crust.

Ore

A mineral from which a metal can be extracted profitably and economically without loss.

Gangue

The unwanted rocky material, sand, soil, and impurities present in and contaminating mined ore.

Three Main Stages of Metallurgy

The sequential extraction stages: 1. Concentration or dressing of the ore, 2. Extraction of crude metal, and 3. Refining or purification of the metal.

Roasting

A pyrochemical process where an ore (typically a sulphide ore) is heated strongly in the excess of air or oxygen below its melting point to convert it into a metal oxide.

Calcination

A pyrochemical process where an ore (typically a carbonate ore) is heated strongly in the absence or limited supply of air to cause decomposition into a metal oxide.

Smelting

A pyrochemical process where ore is mixed with flux and fuel and strongly heated to obtain the metal in a molten state.

Flux

A substance added to the ore during smelting to remove gangue by reacting with it.

Slag

The removable compound formed when a flux reacts with gangue ($\text{Flux} + \text{Gangue} = \text{Slag}$), such as basic flux ($\text{CaO}$) reacting with acidic gangue ($\text{SiO}_2$).

Hearth

The part of a furnace where the ore is kept for heating.

Fire box

The chamber or part of a furnace where the fuel burns.

Chimney

The outlet of a furnace designed for releasing waste flue gases.

Poling

A metal refining method in which molten metal is stirred with green wood logs to eliminate impurities as gas or scum (slag).

Thermite Reaction

A highly exothermic reaction of iron oxide ($\text{Fe}_2\text{O}_3$) with aluminium ($\text{Al}$) that produces molten iron, used to join railway tracks or cracked machine parts.

Corrosion

The slow eating away of metals by the action of air, moisture, or chemicals, such as the rusting of iron or the green coating formed on copper.

Rust

Hydrated ferric oxide or hydrated iron(III) oxide, having the formula $\text{Fe}_2\text{O}_3 \cdot x\text{H}_2\text{O}$.

Anodic Reaction (Rusting of Iron)

The oxidation reaction occurring at an anode spot on the iron object during corrosion: $2\text{Fe} \rightarrow 2\text{Fe}^{2+} + 4e^{-}$.

Cathodic Reaction (Rusting of Iron)

The reduction reaction occurring at a cathode spot during corrosion: $\text{O}_2 + 4\text{H}^{+} + 4e^{-} \rightarrow 2\text{H}_2\text{O}$.

Methods of Corrosion Prevention

Techniques to stop oxidation of metals, including coating the surface with paint or chemicals (like bisphenol), electroplating with other metals ($\text{Sn, Zn}$), or using a sacrificial electrode ($\text{Mg, Zn}$).

Stainless Steel

An alloy of iron, nickel, and chromium that does not rust.

22-carat Gold

An alloy consisting of 22 parts pure gold and 2 parts silver or copper, utilized to provide sufficient hardness for making jewelry.

Extraction of Highly Reactive Metals

The extraction of top activity series metals ($\text{K, Na, Ca, Mg, Al}$) through electrolytic reduction of their molten or fused compounds.

Extraction of Moderately Reactive Metals

The extraction of middle activity series metals ($\text{Zn, Fe, Pb, Cu}$) by roasting sulphides or calcining carbonates to form oxides, followed by reduction using carbon or carbon monoxide.

Extraction of Low Reactivity Metals

The recovery of bottom activity series metals ($\text{Ag, Hg, Pt, Au}$) through heating alone or chemical displacement from aqueous solutions.

Refining Methods (D-P-L-E)

The primary purification methods for crude metals: Distillation, Poling, Liquation, and Electrolytic refining.

PANIC Rule

A mnemonic for electrolytic cells standing for 'Positive Anode, Negative Is Cathode,' where impure metal serves as the anode and pure metal serves as the cathode.

Chalcogen Family

The oxygen-sulphur group elements found in Group 16 ($16^{\text{th}}$ group) of the periodic table.

Bauxite

The principal aluminium ore, having the chemical formula $\text{Al}_2\text{O}_3 \cdot 2\text{H}_2\text{O}$.

Cinnabar

The sulphide ore of mercury, represented by the chemical formula $\text{HgS}$.

Galena

The sulphide ore of lead, represented by the chemical formula $\text{PbS}$.

Blast Furnace Smelting of Iron

The process in which haematite ore ($\text{Fe}_2\text{O}_3$) is reduced in a blast furnace using coke as fuel and limestone ($\text{CaCO}_3$) as flux.