9.5.2
Preventing Corrosion
Preventing Corrosion
Preventing Corrosion
There are three main methods used to stop metals corroding.


Coatings
Coatings
- We can prevent corrosion by applying a coating that acts as a barrier, such as greasing, painting or electroplating.
- E.g. Aluminium has an oxide coating that protects the metal from further corrosion by preventing the metal's surface coming into contact with oxygen and water.
- A disadvantage is that any damage to the coating will lead to the metal becoming exposed and so corrosion will take place.


Sacrificial method
Sacrificial method
- In the sacrificial method, a metal that requires protection will have a more reactive metal attached to it.
- The metal is attached to a more reactive metal and the more reactive metal will undergo oxidation, leaving the less reactive metal intact.
- This means that water and oxygen will stop reacting with the protected metal as they are too busy reacting with the sacrificial metal!


Galvanising
Galvanising
- Galvanising is a hybrid of coatings and the sacrificial method.
- The metal that needs protecting is sprayed with a more reactive metal (e.g. zinc).
- This initially acts as a coating.
- If the more reactive metal is damaged, it will continue to protect as a sacrificial metal.
1States of Matter
1.1Solids, Liquids, & Gases
2Atoms, Elements & Compounds
2.1Elements, Compounds & Mixtures
2.2Atomic Structure & the Periodic Table
2.3Isotopes
2.4Ions & Ionic Bonds
2.5Simple Molecules & Covalent Bonds
2.6Giant Covalent Structures
2.7Metallic Bonding
3Stoichometry
3.1Formulae
3.2Relative Masses of Atoms & Molecules
3.3The Mole & the Avogadro Constant
3.3.1Introducing Moles
3.3.2Amounts of Substances
3.3.3Moles & Equations
3.3.4Calculations Involving Gases
3.3.5Calculating Stoichiometric Reacting Masses
3.3.6Calculating the Moles of Solute
3.3.7Calculating Empirical Formula
3.3.8Chemical Equations
3.3.9Percentage Yield
3.3.10Calculating Yield
3.3.11Percentage Purity
4Electrochemistry
4.1Electrolysis
4.1.1Electrolytic Process
4.1.2Electrolysis Examples
4.1.3Electrolysis of a Binary Compound in Molten State
4.1.4Electroplating
4.1.5Transfer of Charge During Electrolysis
4.1.6Electrolysis of Aqueous Solutions
4.1.7Electrolysis of Copper Sulfate
4.1.8Electrolysis of Halide Compounds
4.1.9Half-Equations
4.1.10Combustion of Hydrocarbons
4.2Hydrogen–Oxygen Fuel Cells
5Chemical Energetics
6Chemical Reactions
6.1Physical & Chemical Changes
6.2Rate of Reaction
6.3Reversible Reactions & Equilibrium
6.3.1Reversible Reactions
6.3.2Conditions & Equilibrium
6.3.3Dynamic Equilibrium
6.3.4Changing Conditions - Heat & Water Effects
6.3.5Factors Affecting Equilibria - Temperature
6.3.6Factors Affecting Equilibria - Pressure
6.3.7Factors Affecting Equilibria - Concentration
6.3.8The Haber Process
6.3.9The Haber Process Equation
7Acids, Bases & Salts
7.1The Characteristic Properties of Acids & Bases
7.1.1Acids & Alkali
7.1.2Reactions of Metals with Acids
7.1.3Reactions of Bases with Acids
7.1.4Reactions of Carbonates with Acids
7.1.5Identifying Acids
7.1.6Properties & Effects of Acids
7.1.7Properties of Bases - Reactions with Acids & Salts
7.1.8Properties of Alkalis & Indicators
7.1.9Strong vs Weak Acids
7.1.10Strong vs Weak Bases
7.1.11Understanding Universal Indicator Paper
7.1.12Acids, Bases & the Neutralisation Reaction
8The Periodic Table
8.1Arrangement of Elements
8.2Group I Properties
8.3Group VII Properties
8.4Transition Elements
8.5Noble Gases
9Metals
9.1Properties of Metals
9.2Uses of Metals
9.3Alloys & Their Properties
9.4Reactivity Series
9.5Corrosion of Metals
9.6Extraction of Metals
10Chemistry of the Environment
10.1Water
10.2Fertilisers
11Organic Chemistry
11.1Formulae, Functional Groups & Terminology
11.2Naming Organic Compounds
11.3Fuels
11.4Alkanes
11.5Alkenes
11.6Alcohols
11.7Carboxylic Acids
11.8Polymers
11.8.1Polymers
11.8.2Problems With Polymers
11.8.3Polymers & Plastics
11.8.4Problems with Plastics
11.8.5Condensation Polymerisation
11.8.6Condensation Polymerisation Examples
11.8.7Addition Polymerisation
11.8.8Addition Polymerisation Examples
11.8.9Structure of Polymers
11.8.10Natural Polyamides - Proteins & Amino Acids
12Experimental Techniques & Chemical Analysis
12.1Experimental Design
12.2Acid-base Titrations
12.3Chromatography
12.4Separation & Purification
12.5Identification of Ions & Gases
12.5.1Testing Aqueous Cations 1
12.5.2Testing Aqueous Cations 2
12.5.3Testing Cations - Flame Tests
12.5.4Testing Cations
12.5.5Testing for Aqueous Cations
12.5.6Testing Anions - Sulfates
12.5.7Testing Anions - Nitrates
12.5.8Testing Gases - Hydrogen
12.5.9Testing Gases - Oxygen
12.5.10Testing Gases - Carbon Dioxide
12.5.11Testing Gases - Chlorine
12.5.12Identifying Gases
Jump to other topics
1States of Matter
1.1Solids, Liquids, & Gases
2Atoms, Elements & Compounds
2.1Elements, Compounds & Mixtures
2.2Atomic Structure & the Periodic Table
2.3Isotopes
2.4Ions & Ionic Bonds
2.5Simple Molecules & Covalent Bonds
2.6Giant Covalent Structures
2.7Metallic Bonding
3Stoichometry
3.1Formulae
3.2Relative Masses of Atoms & Molecules
3.3The Mole & the Avogadro Constant
3.3.1Introducing Moles
3.3.2Amounts of Substances
3.3.3Moles & Equations
3.3.4Calculations Involving Gases
3.3.5Calculating Stoichiometric Reacting Masses
3.3.6Calculating the Moles of Solute
3.3.7Calculating Empirical Formula
3.3.8Chemical Equations
3.3.9Percentage Yield
3.3.10Calculating Yield
3.3.11Percentage Purity
4Electrochemistry
4.1Electrolysis
4.1.1Electrolytic Process
4.1.2Electrolysis Examples
4.1.3Electrolysis of a Binary Compound in Molten State
4.1.4Electroplating
4.1.5Transfer of Charge During Electrolysis
4.1.6Electrolysis of Aqueous Solutions
4.1.7Electrolysis of Copper Sulfate
4.1.8Electrolysis of Halide Compounds
4.1.9Half-Equations
4.1.10Combustion of Hydrocarbons
4.2Hydrogen–Oxygen Fuel Cells
5Chemical Energetics
6Chemical Reactions
6.1Physical & Chemical Changes
6.2Rate of Reaction
6.3Reversible Reactions & Equilibrium
6.3.1Reversible Reactions
6.3.2Conditions & Equilibrium
6.3.3Dynamic Equilibrium
6.3.4Changing Conditions - Heat & Water Effects
6.3.5Factors Affecting Equilibria - Temperature
6.3.6Factors Affecting Equilibria - Pressure
6.3.7Factors Affecting Equilibria - Concentration
6.3.8The Haber Process
6.3.9The Haber Process Equation
7Acids, Bases & Salts
7.1The Characteristic Properties of Acids & Bases
7.1.1Acids & Alkali
7.1.2Reactions of Metals with Acids
7.1.3Reactions of Bases with Acids
7.1.4Reactions of Carbonates with Acids
7.1.5Identifying Acids
7.1.6Properties & Effects of Acids
7.1.7Properties of Bases - Reactions with Acids & Salts
7.1.8Properties of Alkalis & Indicators
7.1.9Strong vs Weak Acids
7.1.10Strong vs Weak Bases
7.1.11Understanding Universal Indicator Paper
7.1.12Acids, Bases & the Neutralisation Reaction
8The Periodic Table
8.1Arrangement of Elements
8.2Group I Properties
8.3Group VII Properties
8.4Transition Elements
8.5Noble Gases
9Metals
9.1Properties of Metals
9.2Uses of Metals
9.3Alloys & Their Properties
9.4Reactivity Series
9.5Corrosion of Metals
9.6Extraction of Metals
10Chemistry of the Environment
10.1Water
10.2Fertilisers
11Organic Chemistry
11.1Formulae, Functional Groups & Terminology
11.2Naming Organic Compounds
11.3Fuels
11.4Alkanes
11.5Alkenes
11.6Alcohols
11.7Carboxylic Acids
11.8Polymers
11.8.1Polymers
11.8.2Problems With Polymers
11.8.3Polymers & Plastics
11.8.4Problems with Plastics
11.8.5Condensation Polymerisation
11.8.6Condensation Polymerisation Examples
11.8.7Addition Polymerisation
11.8.8Addition Polymerisation Examples
11.8.9Structure of Polymers
11.8.10Natural Polyamides - Proteins & Amino Acids
12Experimental Techniques & Chemical Analysis
12.1Experimental Design
12.2Acid-base Titrations
12.3Chromatography
12.4Separation & Purification
12.5Identification of Ions & Gases
12.5.1Testing Aqueous Cations 1
12.5.2Testing Aqueous Cations 2
12.5.3Testing Cations - Flame Tests
12.5.4Testing Cations
12.5.5Testing for Aqueous Cations
12.5.6Testing Anions - Sulfates
12.5.7Testing Anions - Nitrates
12.5.8Testing Gases - Hydrogen
12.5.9Testing Gases - Oxygen
12.5.10Testing Gases - Carbon Dioxide
12.5.11Testing Gases - Chlorine
12.5.12Identifying Gases
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