Understanding Corrosion: Types, Mechanisms, and Control

Corrosion

Destructive attack of metals by the environment.

Electrochemical Theory

Mechanism explaining corrosion via electrochemical interactions.

Galvanic Series

Ranking of metals based on corrosion potential.

Galvanic Corrosion

Corrosion due to two different metals in contact.

Pitting Corrosion

Localized corrosion forming small pits on metal.

Intergranular Corrosion

Corrosion along grain boundaries of metals.

Stress Corrosion

Cracking due to tensile stress and corrosive environment.

Corrosion Inhibitors

Substances that reduce the rate of corrosion.

Cathodic Protection

Technique using a sacrificial anode to prevent corrosion.

Anodic Protection

Method to protect metals by making them anodes.

Metal Coating

Applying a protective layer to prevent corrosion.

Dry Corrosion

Corrosion occurring in the absence of moisture.

Wet Corrosion

Corrosion occurring in the presence of moisture.

Galvanizing

Coating steel with zinc to prevent corrosion.

Tinning

Coating iron or steel with tin for protection.

Organic Coatings

Protective layers made from carbon-based materials.

Inorganic Coatings

Protective layers made from non-carbon materials.

Rusting of Iron

Formation of Fe2O3.H2O from iron and oxygen.

Tarnishing of Silver

Formation of Ag2S from silver and sulfur compounds.

Scales on Copper

Formation of Cu2(OH)2CO3 from copper and compounds.

Corrosion Cost

Annual losses due to corrosion, 3-4% of GDP.

Human Safety

Corrosion-related failures can lead to loss of life.

Material Conservation

Corrosion affects supply of earth's material resources.

Corrosion Science

Study of corrosion mechanisms and processes.

Corrosion Engineering

Application of scientific knowledge for corrosion prevention.

Interdisciplinary Area

Combines chemistry, materials science, and mechanics.

Corrosion Mechanisms

Processes explaining how corrosion occurs.

Corrosion-resistant Alloys

Alloys designed to withstand corrosion effects.

Surface Treatments

Methods to enhance material resistance to corrosion.

Corrosion Control Measures

Strategies to mitigate corrosion impacts.

Maintenance Costs

Expenses incurred for repairing corrosion damage.

Plant Shutdowns

Temporary halts in production due to corrosion.

Contamination Loss

Loss of products due to corrosion-related leaks.

Environmental Pollution

Pollution caused by dumping contaminated products.

Dry Corrosion

Corrosion without the presence of moisture.

Electrochemical Corrosion

Corrosion involving electron flow in conductive solutions.

Oxidation Corrosion

Corrosion from direct reaction with dry oxygen.

Stable Oxide Film

Protective layer preventing further oxidation.

Unstable Oxide Film

Decomposes, allowing continued oxidation.

Volatilization of Oxide

Oxide layer evaporates, increasing corrosion rate.

Corrosion by Gases

Corrosion caused by gases like SO2 and Cl2.

Liquid Metal Corrosion

Corrosion from molten metals at high temperatures.

Anodic Area

Electrode where oxidation occurs in corrosion.

Cathodic Area

Electrode where reduction occurs in corrosion.

Conducting Medium

Substance allowing electron flow in corrosion.

Corrosion Consequences

Negative effects of corrosion on structures and safety.

Corrosion

Degradation of metals due to environmental reactions.

Electrochemical Theory

Corrosion occurs via coupled electrochemical half-cells.

Anodic Area

Site of oxidation where metal dissolves.

Cathodic Area

Site of reduction where electrons are consumed.

Microgalvanic Cells

Small electrochemical cells formed on metal surfaces.

Driving Force

Potential difference causing electron flow between areas.

Anodic Reaction

Metal oxidation releasing electrons into solution.

Cathodic Reaction

Reduction processes consuming electrons from anodic area.

Hydrogen Evolution

Production of hydrogen gas in acidic conditions.

Oxygen Reduction

Reduction of oxygen in neutral environments.

Electrolytic Conduction

Current conduction through dissolved ions in solution.

Rusting

Corrosion of iron in moisture and oxygen presence.

Ferrous Hydroxide

Corrosion product formed from Fe2+ and OH−.

Yellow Rust

Hydrated ferric oxide formed with sufficient oxygen.

Black Magnetite

Anhydrous corrosion product formed with limited oxygen.

Overall Rusting Reaction

2Fe + O2 + 2H2O → 2Fe2+ + 2OH−.

Anodic Oxidation Reaction

Fe → Fe2+ + 2e− at anodic sites.

Cathodic Oxygen Reaction

O2 + 2H2O + 4e− → 4OH− at cathodic sites.

Corrosion Current

Electron flow from anodic to cathodic areas.

Conducting Medium

Solution facilitating electron transfer between sites.

Metal Ion Reduction

Rare process involving deposition of metal ions.

Dissimilar Metals Corrosion

Corrosion occurring when different metals contact.

Conducting Solution

Liquid medium allowing ionic movement for corrosion.

Yellow Rust

Hydrated iron(III) oxide, Fe2O3.3H2O.

Black Rust

Anhydrous magnetite, Fe3O4.3H2O.

Dry Corrosion

Corrosion from atmospheric gases without moisture.

Wet Corrosion

Corrosion requiring a corrosive medium.

Galvanic Series

Ordered list of metals' corrosion potentials.

Electrochemical Series

Ranking of metals by electrode potential.

Oxidation Corrosion

Corrosion due to oxidation reactions.

Liquid Metal Corrosion

Corrosion caused by liquid metal contact.

Pitting Corrosion

Localized corrosion forming small pits.

Stress Corrosion

Cracking due to tensile stress and corrosion.

Intergranular Corrosion

Corrosion along grain boundaries in metals.

Corrosion Resistance

Material's ability to withstand corrosion.

Corrosive Medium

Substance that promotes corrosion, like water.

Corrosion Product

Material formed as a result of corrosion.

Passivity

State where metal becomes resistant to corrosion.

Electrode Potential

Voltage difference at an electrode in solution.

Dissimilar Metals

Metals with different corrosion potentials.

Aqueous Electrolyte

Liquid solution that conducts electricity.

Copper-Steel Corrosion

Galvanic corrosion example with copper and steel.

Corrosion Behavior of Alloys

Alloys' response to corrosion in environments.

Hydrated Iron Oxide

Iron oxide containing water molecules.

Galvanic Corrosion

Corrosion due to two dissimilar metals in contact.

Zinc-Coated Screws

Screws protected by a layer of zinc.

Copper Sheet

A flat piece of copper metal.

Stainless Steel Screw

Corrosion-resistant screw made of stainless steel.

Cadmium Plated Steel Washer

Steel washer coated with cadmium for protection.

Steel Propeller Shaft

Shaft made of steel for propelling mechanisms.

Bronze Bearing

Bearing made from bronze, used for support.

Moisture Effect

Corrosion severity increases with moisture presence.

Coastal Corrosion

Higher corrosion rates near coastal areas.

Conductive Electrolyte

Substance that facilitates electrical conductivity in corrosion.