Non-Ferrous Metal Production and Metallurgy

Vocabulary flashcards covering the extraction, properties, processing, corrosion prevention, and phase equilibria of non-ferrous metals including aluminium, copper, and zinc.

Non-Ferrous Metals

Metals and alloys that do not contain iron as their main constituent; generally costlier than iron and steel and specified when distinct engineering properties—such as corrosion resistance, light weight, or electrical conductivity—are required.

Wrought Aluminium Alloys

Lightweight, economical, and corrosion-resistant alloys used in civil engineering construction such as bridges and roofs where high strength is not mandatory, providing approximately a $50\%$ weight saving compared to steel.

Bauxite

The principal ore of aluminium with the chemical formula $Al_2O_3 \cdot nH_2O$, naturally associated with impurities such as silica, titania, clay, titanium oxide, and iron.

Bayer's Process

The Stage 1 chemical purification process in which powdered bauxite ore is treated with sodium hydroxide ($NaOH$) solution in a pressure vessel at $170^\circ\text{C}-180^\circ\text{C}$ to form soluble sodium aluminate ($Na[Al(OH)_4]$) while filtering out insoluble red mud.

Serpak's Process

A bauxite purification method in which powdered ore is heated with coke at $1800^\circ\text{C}$ in an atmosphere of nitrogen to eliminate impurities and obtain purified aluminium oxide.

Hall-Heroult Process

Stage 2 electrolytic reduction of aluminium wherein alumina dissolved in molten cryolite is electrolyzed in a carbon-lined pot (cathode) with carbon anode rods at $953^\circ\text{C}$, producing $99\%$ pure molten aluminium.

Cryolite

Sodium aluminium fluoride ($Na_3AlF_6$), used as a molten electrolyte solvent in the Hall-Heroult cell to dissolve alumina ($Al_2O_3$) and facilitate electrolysis at an operational temperature of $953^\circ\text{C}$.

Anodizing

An electrolytic passivation process that converts the surface of an aluminium part into an exceptionally hard, corrosion-resistant cellular aluminium oxide ($Al_2O_3$) layer less than $1\,\text{mm}$ thick using an acid electrolyte and lead cathode.

Super Duralumin

A high-performance aluminium alloy designed for structural components in the aircraft industry.

Chalcopyrite

A common sulphide ore of copper having the chemical formula $CuFeS_2$, containing approximately $34.5\%$ copper.

Chalcocite

A sulphide ore of copper having the chemical formula $Cu_2S$, containing approximately $79.8\%$ copper.

Cuprite

An oxide ore of copper having the chemical formula $Cu_2O$, containing approximately $88.8\%$ copper.

Froth Flotation

A mineral concentration method where powdered ore is immersed in a water and oil bath agitated with blown air; mineral particles rise in the oily froth to concentrate copper up to $90\%$, while gangue impurities sink.

Roasting

A thermal metallurgical treatment in which powdered ore is heated below its melting point in a furnace in a current of air to expel volatile impurities, such as converting sulphides to oxides and evolving $SO_2$.

Copper Matte

A dense molten mixture of copper sulphide and iron sulphide that settles below the iron silicate slag during the smelting of roasted copper ore in a reverberatory or blast furnace.

Blister Copper

A crude, porous grade of metallic copper ($\sim 98\%-99\%$ purity) produced in a Bessemer converter by the reaction $2Cu_2O + 2Cu_2S \rightarrow 8Cu + SO_2$, named after the blistered surface caused by escaping $SO_2$ gas.

Electrolytic Refining of Copper

A purification technique in which cast blister copper anode plates dissolve into a copper sulphate electrolyte and deposit onto pure copper cathode sheets under an electric current, yielding a purity of around $99.95\%$ to $99.99\%$.

Sphalerite

The chief sulphide ore of zinc with the formula $ZnS$, containing approximately $67\%$ zinc.

Retort Smelting of Zinc

A pyrometallurgical reduction process where roasted zinc ore ($ZnO$) and coal are placed in retort vessels, heated to $1450^\circ\text{C}$ to vaporize zinc ($ZnO + C \rightarrow Zn + CO$), and condensed into liquid zinc.

Spelter Zinc

Crude metallic zinc obtained by the condensation and solidification of vaporized zinc distillate from pyrometallurgical retorts.

Hydrometallurgical Process (Zinc)

A chemical extraction route where roasted zinc ore is leached with sulphuric acid, filtered, treated with lime to precipitate iron and aluminium impurities, and subsequently electrolyzed to recover pure zinc.

Galvanizing

The process of coating iron or steel with a protective sacrificial layer of zinc by methods such as hot dipping, accounting for roughly $40\%$ of total world zinc production.

Brass

A non-ferrous alloy predominantly composed of copper ($65\%-90\%$) and zinc ($10\%-35\%$), consuming $20\%$ of global zinc production for plumbing, decorative fittings, and instruments.

Bronze

A copper-base alloy consisting primarily of copper ($78\%-95\%$) and tin ($5\%-22\%$), widely used for bearings, medals, instruments, and guitar strings.

Corrosion

The deterioration of a metal as a result of chemical or electrochemical reactions between the metal and its surrounding environment, wasting approximately $2\%$ of total metal produced annually.

Rusting of Iron

The electrochemical degradation of iron and steel in humid air and rain forming ferric hydroxide ($4Fe + 6H_2O + 3O_2 \rightarrow 4Fe(OH)_3$), which dehydrates into red rust ($Fe_2O_3 \cdot 3H_2O$).

Corrosion Inhibitors

Chemical substances added to aggressive liquid environments (such as boiler-feed water) that decrease the corrosion rate of exposed metal structures.

Inactive Coating

A protective barrier covering—such as enamel paint, plastic coating, bituminous paint, oil, or grease—that insulates the base metal without undergoing chemical reactions after application.

Active Coating

A protective metallic coating (such as zinc galvanizing) that enters into chemical reaction with atmospheric moisture and gases to form an adherent, insoluble protective compound (such as zinc carbonate).

Electroplating

An electrochemical coating technique in which an external electrical current dissolves metal from an anode and deposits a uniform metallic coating onto a workpiece acting as the cathode.

Cementation (Sherardizing)

A protective coating method for delicate metal parts where objects are placed into a drum packed with metallic dust (such as zinc powder) and heated together for several hours.

Cladding

A mechanical joining process where a corrosion-resistant coating metal sheet is bonded to a core metal surface by passing both layers together through rollers at elevated temperatures.

Tie Line

An isothermal horizontal line drawn across a two-phase region on a binary phase diagram to determine the equilibrium chemical compositions of both coexisting phases at that temperature.

The Lever Rule

A mathematical relationship derived from mass conservation ($W_L = \frac{C_\alpha - C_o}{C_\alpha - C_L}$ and $W_\alpha = \frac{C_o - C_L}{C_\alpha - C_L}$) used to calculate the relative weight fractions of two coexisting phases along a tie line.

Pb-Sn Eutectic System

A binary alloy system demonstrating a eutectic reaction where liquid of composition $61.9\,\text{wt\%}\,Sn$ transforms simultaneously upon cooling at $183^\circ\text{C}$ into solid $\alpha$ ($19.2\,\text{wt\%}\,Sn$) and solid $\beta$ ($97.5\,\text{wt\%}\,Sn$).

Nitinol

A shape memory alloy composed of $50\%-55\%$ nickel and $45\%-50\%$ titanium that recovers its original geometric shape upon heating, commonly used in eyeglass frames.

Cupronickel

A copper-nickel alloy containing $70\%-90\%$ copper and $10\%-30\%$ nickel, known for its outstanding corrosion resistance in seawater and used in marine engineering and coinage.