electrochemical corrosion It refers to the corrosion damage of metal materials caused by the action of corrosive battery when metal materials contact with electrolyte.Because the environment of electrochemical corrosion is very common in practice, electrochemical corrosion is the most common phenomenon in the corrosion of metal materials.The essence of electrochemical corrosion is immersionelectrolyte solutionThe anodic oxidation dissolution on the metal surface in the solution is accompanied by the reduction of depolarizer on the metal surface, and the corrosion damage law follows the electrochemical corrosion principle[1]。
type
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Corrosion batteries are generally divided into three categories according to the size of the electrodes that make up the corrosion battery, the main influencing factors that form the corrosion battery and the characteristics of corrosion damage:Macroetch cell, micro corrosion battery and ultra micro corrosion battery.
(1) Macroetch cell
This type of corrosion battery is usually composed of electrodes visible to the naked eye.It has the characteristics that the cathode area and anode area remain stable for a long time, and often produce obvious local corrosion.
Due to the electrochemical inhomogeneity of the metal surface, many tiny electrodes are generated on the metal surface, which forms various micro corrosion batteries, referred to as micro batteries.
(3) Ultramicro etching cell
The so-called ultramicro corrosion battery refers to the corrosion battery formed due to the existence of ultramicro electrochemical non-uniformity on the metal surface, which produces many ultramicro electrodes.It is the cause of electrochemical uniform corrosion of metal materials[1]。
Work history
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It can be seen from the formation of corrosion cell that a corrosion cell must include cathode, anodeelectrolyte solutionAnd the electronic conductor connecting the cathode and anode.These components constitute three basic processes of the working process of corrosion battery.
(1) Anodic process.The metal is dissolved in the form of ions and enters the solution. Electrons of equal charge remain on the metal surface and migrate to the cathode area through the electronic conductor, that is, the anodic oxidation reaction occurs;
(2) Cathodic process.The material in the electrolyte solution that can accept electrons captures electrons from the surface of the metal cathode to generate new materials, that is, the cathode undergoes a reduction reaction;
(3) Transfer of electric charge.The transfer of charge in metal depends on the flow of electrons from anode to cathode;In solution, it depends on the electromigration of ions.
In this way, the whole battery system forms a circuit through the reaction of cathode and anode and the flow of electric charge, and the anode process can continue to corrode the metal.The above three basic processes involved in the operation of corrosion batteries are not only independent of each other, but also closely related to each other.As long as one of the processes is blocked and cannot be carried out, the other two processes will also be blocked and stop, resulting in the termination of the entire corrosion process[2]。
characteristic
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(1) The corrosion of metal is concentrated inAnode area，Cathode regionIt only plays the role of transferring electrons;
(2) The three processes of reaction are independent and related to each other;
(3) The reaction in the corrosive cell is carried out in an irreversible manner to the maximum extent[2]。
