SC13 Transition metals, alloys and corrosion mind map

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Metal selection

Transition block: Fe / Cu / Ni; typically dense, strong, high melting points
Compounds / catalysis: Often coloured; Fe catalyses Haber process; not used up overall
Copper: Good electrical / thermal conductor; drawn into wires
Aluminium / gold: Al: light / protective oxide; Au: unreactive / soft / costly
Choose from data: Strength, density, conductivity, corrosion, price / environment

Corrosion

Oxidation: Metal reacts with surroundings; rusting is iron corrosion
Rust conditions: Both water AND O₂; salt speeds process; control variables
Evidence: Moist air vs dry air vs boiled water protected by oil
Barriers: Paint / oil / grease / plastic exclude water / O₂; damage matters
Zinc / magnesium: More reactive sacrificial metal oxidises; eventually replace
Tin comparison: Intact barrier protects; scratch can accelerate iron corrosion

Electroplating

Object: Negative cathode; metal cations gain electrons / deposit
Copper electrodes: Cathode: Cu²⁺ + 2e⁻ → Cu; anode replaces Cu²⁺
Control coating: Clean object; controlled current / time; appearance / protection

Alloys

Structure: Mixed sizes distort layers → harder for layers to slide
Steel: Carbon / other additions; chromium helps stainless protection
Examples: Brass: Cu / Zn; magnalium: Al / Mg
Trade-offs: Gold harder; copper may lose conductivity; evaluate data
Composition: Element mass ÷ total alloy mass × 100

Connections

Corrosion → Electroplating: Protective metal coatings depend on electrode choice and corrosion behaviour.
Metal selection → Alloys: Alloy composition changes the properties used to select materials.