Lectures on Electrochemical Corrosion

1. Introduction to Corrosion.- 1.1. Economic and Technical Significance.- 1.2. Complexity of Corrosion Phenomena.- 1.2.1. Iron in the Presence of Different Aqueous Solutions.- 1.2.2. Iron Filings in a Solution of NaOH.- 1.2.3. Iron in Nitric Acid Solutions.- 1.2.4. Iron as an Anode or Cathode in an Electrolytic Cell.- 1.2.5. Iron in Contact with Different Metals.- 1.2.6. Zinc in Contact with Distilled Water.- 1.3. Influence of Oxidants, Electric Currents, Motion of Solutions.- 1.3.1. Oxidants.- 1.3.2. Influence of Electric Current.- 1.3.3. Influence of Motion of Solution.- 1.4. Application of Chemical Thermodynamics.- 1.5. Application of Electrochemical Thermodynamics.- 2. Chemical and Electrochemical Reactions.- 3. Chemical Equilibria.- 3.1. General Formula of Chemical Equilibria.- 3.2. Influence of pH on Chemical Equilibria. Graphic Representation.- 3.2.1. Influence of pH on the Equilibrium of Homogeneous Systems.- 3.2.1.1. Dissociation of Solutions Weak Acids or Weak Bases.- 3.2.1.2. Applications.- 3.2.1.2.1. The Use of pH Indicators.- 3.2.1.2.2. Buffering Effect.- 3.2.1.2.3. Hydrolysis.- 3.2.1.2.4. pH of Solutions of Weak Acids or Weak Bases.- 3.2.1.2.4.1. General Remarks.- 3.2.1.2.4.2. Graphic Determination of the Influence of pH on the Concentration of Substances Able to Exist in Several Dissolved Forms.- 3.2.1.2.4.3. Examples.- 3.2.2. Influence of pH on the Equilibrium of Heterogeneous Solid-Solution Systems.- 3.2.2.1. Solubility of Oxides and Hydroxides.- 3.2.2.2. pH of Oxide and Hydroxide Solutions.- 3.2.2.3. pH of Solutions of Metallic Salts.- 3.2.2.4. Solubility of Salts of Weak Acids.- 3.2.2.5. Application: Saturation Equilibria of Calcium Carbonate and the Treatment of Aggressive Water.- 3.2.3. Influence of pH on the Equilibria of Heterogeneous Gas-Solution Systems.- 3.2.3.1. Solubility of Acid and Alkaline Gases.- 3.2.3.2. Applications.- 3.2.3.2.1. Action of Strong Acids on Solutions of Carbonates, Sulfites, and Sulfides.- 3.2.3.2.2. Action of Strong Bases on Ammoniacal Solutions.- 3.2.3.2.3. Absorption of Acidic or Alkaline Gases.- 4. Electrochemical Equilibria.- 4.1. Electrochemical Oxidations and Reductions.- 4.1.1. Decomposition of Water.- 4.1.2. Synthesis of Water.- 4.1.3. Corrosion of Iron or Zinc by an Acid with Evolution of Hydrogen.- 4.1.4. Oxidation of Ferrous Salts by Permanganate.- 4.2. Galvanic Cells.- 4.2.1. General Remarks.- 4.2.2. Equilibrium Potential and Electromotive Force of a Galvanic Cell.- 4.2.3. Fuel Cells, Batteries, Electrolysis Cells.- 4.3. Any Electrochemical Reaction.- 4.3.1. Equilibrium Potential of an Electrochemical Reaction.- 4.3.2. General Formula of Electrochemical Equilibria.- 4.3.3. Influence of Electrode Potential on Electrochemical Equilibria.- 4.3.3.1. Influence of the Potential on the Equilibrium of Homogeneous Systems-"Oxidation-Reduction Potentials".- 4.3.3.2. Influence of the Potential on the Equilibrium of Heterogeneous Solid-Solution Systems-"Dissolution Potentials" of Solid Bodies.- 4.3.3.3. Influence of the Potential on the Equilibrium of Heterogeneous Gas-Solution Systems-"Dissolution Potentials" of Gaseous Bodies.- 4.3.4. Graphic Representations of Electrochemical Equilibria.- 4.3.5. Combined Influence of pH and Electrode Potential on Electrochemical Equilibria. Basis for Diagrams of Electrochemical Equilibria.- 4.3.5.1. Chemical Reactions in Which H+ Ions Participate.- 4.3.5.2. Electrochemical Reactions in Which H+ Ions Do Not Participate.- 4.3.5.3. Electrochemical Reactions in Which H+ Ions Participate.- 4.4. Diagram of Electrochemical Equilibria of Water.- 4.4.1. Thermodynamic Stability of Water: Acid and Alkaline Media; Oxidizing and Reducing Media.- 4.4.2. Decomposition of Water: Formation of Hydrogen, Oxygen, Ozone, and Hydrogen Peroxide.- 4.5. Diagram of Electrochemical Equilibria of Hydrogen Peroxide. Oxidation, Reduction, and Decomposition of Hydrogen Peroxide. Reduction of Oxygen.- 4.6. Diagrams of Electrochemical Equilibria of Metals and Metalloids.- 4.6.1. Diagram of Electrochemical Equilibria of Copper.- 4.6.1.1. Establishment of the Diagram.- 4.6.1.1.1. Standard Free Enthalpies of Formation.- 4.6.1.1.2. Reactions.- 4.6.1.1.3. Conditions of Equilibrium and Graph of Equilibrium Diagram.- 4.6.1.1.3.1. Homogeneous Reactions. Regions of Relative Predominance of Dissolved Bodies.- 4.6.1.1.3.2. Heterogeneous Reactions in Which Two Solid Bodies Participate. Regions of Stability of Solid Bodies.- 4.6.1.1.3.3. Heterogeneous Reactions in Which One Solid Body Participates. Solubility of Solid Bodies.- 4.6.1.1.3.4. Graph of the Overall Diagram.- 4.6.1.1.3.5. Phase Rule.- 4.6.1.2. Interpretation of Diagram. Behavior of Copper in the Presence of Aqueous Solutions.- 4.6.1.2.1. General Bases for Predicting Corrosion, Immunity, and Passivation of Copper.- 4.6.1.2.2. Behavior of Copper in the Presence of an Oxygen-Free Solution of Cupric Sulfate.- 4.6.1.2.3. Influence of pH on the Potential of Copper.- 4.6.1.2.4. Electrolysis of Acidic Copper Solutions.- 4.6.1.2.5. Copper Plating in Cyanide Baths.- 4.6.2. Theoretical Conditions of Corrosion, Immunity, and Passivation.- 4.6.3. Behavior and Equilibrium Diagrams of Copper, Iron, Zinc, Aluminum, Silver, Lead, Tin, Chromium, and Arsenic.- 4.6.3.1. Copper.- 4.6.3.2. Iron.- 4.6.3.3. Zinc.- 4.6.3.4. Aluminum.- 4.6.3.5. Silver.- 4.6.3.6. Lead.- 4.6.3.7. Tin.- 4.6.3.8. Chromium.- 4.6.3.9. Arsenic.- 4.6.4. Nobility of Metals and Metalloids. Theoretical and Practical Bases.- 4.6.4.1. Thermodynamic Basis-Nobility by Immunity; Nobility by Immunity and Passivation.- 4.6.4.2. Actual Conditions of Corrosion and Noncorrosion of Metals.- 4.6.4.2.1. Thermodynamic Nobility and Practical Nobility.- 4.6.4.2.2. Anodic Protection and Cathodic Protection.- 4.6.5. Resistance of Metals to Pure Water.- 4.6.6. Metals Which Can Be Passivated and Activated.- 4.6.7. Oxidizing Corrosion Inhibitors.- 4.6.8. Reference Electrodes.- 4.6.8.1. Introduction.- 4.6.8.2. Calculations Without Activity Coefficients.- 4.6.8.2.1. Standard Hydrogen Electrode.- 4.6.8.2.2. Calomel Electrodes.- 4.6.8.2.3. Silver Chloride Electrodes.- 4.6.8.2.4. Copper Sulfate Electrode.- 4.6.8.3. Calculations Using Activity Coefficients.- 4.6.8.4. Comparison Between Calculated and Measured Electrode Potentials of Reference Electrodes.- 5. Electrochemical Kinetics.- 5.1. General Remarks.- 5.2. Direction of Electrochemical Reactions.- 5.3. Affinity, Overpotential, Rate, and Direction of Electrochemical Reactions. The Second Principle of Electrochemical Thermodynamics.- 5.4. Reaction Currents.- 5.5. Polarization Curves.- 5.5.1. Reversible and Irreversible Reactions: Oxidation Potential, Reduction Potential, and Oxidation-Reduction Potential.- 5.5.2. The Tafel Law. Exchange Current.- 5.5.3. Predetermination of the Direction and Rate of Electro chemical Reactions.- 5.6. Electrochemical Catalysis of Chemical Reactions.- 6. Corrosion and Protection of Iron and Steel.- 6.1. Diagram of Electrochemical Equilibria of the Iron-Water System at 25 C.- 6.2. General Conditions of Corrosion, Immunity, and Passivation of Iron.- 6.3. Polarization Curves.- 6.3.1. Behavior of Iron in the Presence of Oxygen-Free Bicarbonate Solution.- 6.3.2. Behavior of Iron in the Presence of Oxygen-Saturated Bicarbonate Solution.- 6.3.3. Demonstration Experiment: Anodic Corrosion and Passivation of Iron.- 6.3.4. Influence of pH and Electrode Potential on the Behavior of Iron.- 6.4. Behavior of Electrically Insulated Iron.- 6.4.1. Behavior of Iron in the Absence of an Oxidant.- 6.4.2. Behavior of Iron in the Presence of an Oxidant.- 6.4.3. Differential Aeration.- 6.4.3.1. Corrosion Pits.- 6.4.3.2. Waterline Corrosion.- 6.5. Behavior of Iron Coupled to Another Metal.- 6.5.1. Coupling of Iron with a More Noble Metal.- 6.5.1.1. More Noble Metal Not Corroded by the Solution.- 6.5.1.2. More Noble Metal Corroded by the Solution.- 6.5.2. Coupling of Iron with a Less Noble Metal: Cathodic Protection.- 6.6. Protection of Iron and Steel Against Corrosion.- 6.6.1. General Criteria.- 6.6.1.1. Cathodic Protection.- 6.6.1.2. Protection by Passivation; Oxidizing Inhibitors.- 6.6.1.3. Protection by Adsorption Inhibitors.- 6.6.1.4. Other Protection Procedures.- 6.6.2. Electrochemical Techniques for the Study of Corrosion.- 6.6.2.1. Intensiostatic, Potentiostatic, and Potentiokinetic Methods.- 6.6.2.2. General Principles.- 6.6.2.3. Experimental Predetermination of Circumstances of Immunity, General Corrosion, and Localized Corrosion (Pitting).- 6.6.2.4. Linear Polarization Methods.- 6.6.3. Influence of Oxidants, Chlorides, and Orthophosphates.- 6.6.3.1. Influence of Oxygen.- 6.6.3.2. Influence of Chlorides.- 6.6.3.3. Influence of Orthophosphates. Oxidizing Phosphatization.- 6.6.4. Treatment of Corrosive Water.- 6.6.4.1. Drinking Water.- 6.6.4.2. Boiler Water.- 6.6.4.3. Other Industrial Waters.- 6.6.5. Action of Wet Materials.- 6.6.6. Cathodic Protection.- 6.6.6.1. General Principles.- 6.6.6.1.1. Protection by Placing the Metal in a State of Immunity.- 6.6.6.1.2. Protection by Placing the Metal in a State of Perfect Passivation. Protection Against Pitting Corrosion, Crevice Corrosion, and Stress Corrosion Cracking.- 6.6.6.1.2.1. Pitting Corrosion of Copper and Protection.- 6.6.6.1.2.2. Pitting Corrosion, Crevice Corrosion, and Stress Corrosion Cracking of Iron and Steels, and Protection.- 6.6.6.1.3. Protection Procedures Using External Currents and Sacrificial Anodes.- 6.6.6.1.4. Current Requirements for Cathodic Protection.- 6.6.6.2. Applications of Cathodic Protection.- 6.6.6.2.1. Cathodic Protection of Buried Piping.- 6.6.6.2.2. Cathodic Protection of Immersed Structures; Internal Walls of Piping.- 6.6.7. Protection by Corrosion Inhibitors.- 6.6.7.1. General Remarks.- 6.6.7.2. Oxidizing Inhibitors.- 6.6.7.3. Adsorption Inhibitors.- 6.6.7.4. Use of Corrosion Inhibitors.- 6.6.7.4.1. Drinking Water.- 6.6.7.4.2. Central Heating Water.- 6.6.7.4.3. Antifrigerant Solutions.- 6.6.7.4.4. Pickling Baths.- 6.6.7.4.5. Boiler and Packaging Condensates; Volatile Inhibitors.- 6.6.7.4.6. Treatment of Steel Surfaces Before Painting.- 6.6.7.4.6.1. Phosphatization; "Wash Primers".- 6.6.7.4.6.2. Inhibitive Primer Undercoats.- 6.6.7.4.6.3. Zinc Plating.- 6.6.8. Protection by Coatings.- 6.6.9. Other Corrosion Problems.- 7. Further Applications of Electrochemistry to Corrosion Studies.- 7.1. Introduction.- 7.2. Potential-pH Equilibrium Diagrams for Complex Systems Containing Copper at 25 C.- 7.2.1. System Cu-Cl-H2O.- 7.2.2. System Cu-CO2-H2O.- 7.2.3. System Cu-Cl-CO2-SO3-H2O.- 7.3. Diagrams of Electrochemical Equilibria for Molten Salts.- 7.4. The Influence of Temperature on Electrochemical Equilibria. Electrode Potential-Temperature Diagrams.- General Bibliography.- Author Index.