Electrocorrosion and Protection of Metals, 1st Edition
Introduction: Corrosion and electric current – 200 years together.
1. Dependence of the corrosion behavior of metals attacked by an external current on their initial state.
1.1. State of metals in aggressive media in the absence of attack by external currents
1.2. Polarization of metals
1.3. Attack of external anodic current on actively corroding metals
1.4. Attack of external anodic current on passive metals
1.5. Attack of external anodic current on thermodynamically stable metals
1.6. Attack of external cathodic current on metals
1.7. Attack of external alternating current on metals
1.8. External current as a factor of the aggressiveness of the environment2. Corrosion and protection of underground and underwater structures attacked by stray currents.
2.1. Main media, sources of stray currents and objects of their corrosive attack
2.2. Methods of detection and control of stray currents
2.3. Metal corrosion by stray currents
2.4. Protection of metals against corrosion attack by stray currents
2.4.1. Measures for reducing stray currents
2.4.2. Protection of underground structures by electrodrainage
2.4.3. Cathodic protection3. Operating features of electrochemical plants.
3.1. General characteristics of electrochemical plants
3.2. Leakages currents in electrochemical plants
3.2.1. Sources of leakage currents, concepts and problems connected with them
3.2.2. Methods of measuring and controlling of leakage currents
3.2.3. Magnitudes and distribution regularity of leakage currents along the lines of Electrochemical cells
3.3. Aggressive media4. Using structural metallic materials in electrochemical plants without taking into account attack by leakage currents.
4.1. Non-metallic materials
4.2. Traditional metallic materials
4.3. Experience in the field of titanium application
4.3.1. Preconditions for the application of titanium in electrochemical plants
4.3.2. Attempts at titanium application in the zones of attack by leakage currents
4.3.3. Preconditions and experience of titanium application in wet chlorine lines of electrochemical plants
4.3.4. Laboratory and industrial tests of titanium resistance against crevice corrosion in wet chlorine and in chlorine-saturated water. Comparison of results.5. Corrosion behavior investigations of traditional structural metallic materials in electrochemical plant media, taking into account attack by leakage currents.
5.1. Carbon steel in neutral, alkaline and chloride-alkali media
5.1.1. Neutral solutions of salts
5.1.2. Alkaline solutions
5.1.3. Chloride-alkali solutions
5.2. Stainless steel 18-10 in alkaline and acid media
5.2.1. 50% naoh solution at 120oc; comparison of corrosion behavior of SS18-10 and of Nickel
5.2.2. Technological solution for producing sodium perborate
5.2.3. Acid sulfate containing electrolyte for copper electrorefining6. Corrosion behavior investigations of titanium and its alloys in the media of electrochemical plants, taking into account the attack by anodic leakage currents.
6.1. Corrosion and electrochemical characteristics of titanium
6.2. Chloride and chloride-alkali media of chlorine-producing electrochemical plants
6.3. Electrolyte of copper electrorefining
6.4. Media of nickel electrorefining
6.5. Influence of welding seams and crevices
6.5.1. Welding seams
6.5.2. Artificial crevices
6.6. Titanium alloys7. Hydrogenation and corrosion investigations of titanium under attack by an external cathodic current.
7.1. Conditions of hydrogenation and corrosion of titanium. Methodological features of experiments
7.2. Investigations in non-stirred nacl solutions
7.3. Investigations under conditions of electrolyte stirring and flowing
7.3.1. Relation between the corrosion rate of titanium and the accumulation of Oxygen-chlorine compounds in the solution
7.3.2. Two corrosion mechanisms of hydrogenated titanium
7.4. Welding seams
7.5. Hydrogenation of cathode matrixes in solution of nickel electrorefining
7.5.1. Electrochemical investigations of combined discharge of nickel and hydrogen ions on titanium
7.5.2. Radiochemical investigations of titanium hydrogenation in the process of nickel deposition8. Estimation of corrosion stability of structures made of passive metals in aggressive media, in the field of an external current.
8.1. Estimation based on the potential value
8.1.1. Activation potential as an estimation criterion of the passive metal state in the field of an external current
8.1.2. Types of structural elements in the form of tubes in the field of an external current
8.1.3.Potential and current distribution along structural elements in the form of tubes
8.1.4. Computation procedure of potential distribution along the internal tube surface with the help of a computer
8.2. Estimation based on the external current value
8.3. Practical steps and examples of corrosion stability estimation of structures in the form of tubes of different types
8.4. Significance of the electrochemical characteristics of passive metals for the estimation and provision of the corrosion stability of metallic structures9. Electrocorrosion protection of metals in electrochemical plants based on existing methods.
9.1. Insulating coatings
9.2. Reduction of leakage currents coming from electrochemical cells
9.2.1. Reduction of leakage currents along electrolyte piping and prevention of current oscillations
9.2.2. Reduction of leakage currents along piping of wet gases
9.3. Sectionalization of piping made of passive metals
9.4. Possibilities of applying “traditional” methods of electrochemical protection and their modifications for electrochemical plants
9.4.1. Electrodrainage protection
9.4.2. Protection by sacrificial anodes for current drainage in chloride electrolysis plants
9.4.3. Protection by sacrificial anodes for current drainage in electrolysis plants with metal deposition10. New principles of protection of passive metals against electrocorrosion in electrochemical plants.
10.1. Protection of metals with the relationship ∆ = (Eox – Ea) < 0, against corrosion attack by an external anodic current, with the help of dimensionally stable anodes – current leak-offs
10.1.1. Theoretical basis
10.1.2. Experimental verification of the protection principle
10.2. Corrosion protection with the help of dimensionally stable anodes, oriented along the field of the external current
10.2.1. Theoretical basis
10.2.2. Investigation of the protection principle
10.3. Protection of metals against corrosion attack by an external cathodic current
10.4. Protection of metals against corrosion attack by leakage currents which periodically change their direction
10.5. Protection of metals against corrosion attack by external currents at the stage of design11. Electrodes for metal protection against corrosion attack by external currents in electrochemical plants.
11.1. Requirements upon materials of electrodes that are used for protection against corrosion attack by external currents
11.2. Application of dimensionally stable anodes of commercial electrolysis processes for protection against electrocorrosion
11.2.1. Neutral and acid chloride-containing media
11.2.2. Chloride-sulfate media
11.3. Anodes for media containing sulfuric acid
11.4. Dimensionally stable anodes with a coating obtained on the basis of intermetallic compounds produced in electric spark
11.4.1. Preconditions for the choice of materials and methods of producing the anodes. Test conditions
11.4.2. Investigations in chloride solutions
11.4.3. Investigations in chloride-alkali solutions
11.5. Stable cathodes
11.5.1. Cathodes for media containing dissolved chlorine and for chloride media
11.5.2. Titanium cathodes for other aggressive media
11.5.3. Possibilities of increasing the stability of titanium cathode blanks12. Industrial tests and the introduction into electrochemical plants of developed methods for the protection of metals against corrosion attack by leakage currents.
12.1. Protection by sacrificial anodes in electrorefining plants
12.1.1. Industrial tests
12.1.2. Introduction of protection
12.2. Industrial tests and the introduction of corrosion protection of titanium structures by anodes – current leak-offs
12.2.1. Industrial tests
12.2.2. Introduction of protection
12.3. Industrial tests and the introduction of corrosion protection by anodes, oriented along the field of the external current in electrochemical plants
12.3.1. Industrial tests
12.3.2. Introduction of protection
12.4. Industrial tests of titanium protection against corrosion attack by cathodic leakage currents with the help of stable cathodes
12.5. Combined protection of metals against corrosion attack by leakage currents
12.6. Effectiveness and possibilities of using the developed methods of metal protection against electrocorrosionReferences.