Compare the difference between electrochemical corrosion and chemical erosion

In our daily lives, we find many cases of wear and tear or wear due to various causes, typically molded objects often oxidized to rust. People often use paint to prevent this.

1. Chemical corrosion

Chemical corrosion is caused by the metal reacting with water vapor or gas at high temperatures. Or I see people say more difficult as follows

Chemical corrosion is the redox process in which the electrons of the metal are passed directly to the substances in the environment.

Electrochemical corrosion is a redox process in which the metal is corroded by the action of an electrolyte solution that generates electrons that move from the anode to the cathode.

Conditions for electrochemical corrosion:

1) The electrodes must be different. For example Fe and Cu. Strong metals are cathode and are rapidly eroded

2) The electrodes must be in contact with each other (either directly or indirectly via conductor) and in contact with the electrolyte

2. Electrochemical Corrosion

Electrochemical corrosion is the destruction of metal by contact with the electrolyte solution to create an electric current.

For example: the shell of a submerged ship, the conduit placed in the ground, the metal in contact with the humid air ... Thus, electrochemical corrosion is the most common and most severe metal corrosion.

a) Electrochemical Corrosion Conditions: The necessary and sufficient conditions are:

- The electrodes must be different: they may be metal pairs, metal pairs - nonmetals (C), metal pairs - chemical compounds (xmentment). The metal that has a stronger reduction factor is the cathode. So pure metals are difficult to erode.

- The electrodes must be in contact with each other (either directly or indirectly through the conductor)

- The electrodes come in contact with an electrolyte solution

b) Electrochemical Corrosion Mechanisms: Iron or steel are Fe-C alloys, in which cathodes are Fe crystals, cathode-ray crystals. These electrodes come in direct contact with each other and with a liquid electrolyte coating. Thus, corroded objects are electrochemical:

At cathode: Fe atoms are oxidized. These ions are dissolved in an electrolyte solution which has an amount of oxygen, where they are further oxidized.

At the anode: The hydrogen ions of the electrolyte move to the positive charge, where they are reduced to free hydrogen and then released from the solution.

The Fe crystals are oxidized from the outside in turn. After a while, the iron (steel) will be eaten out.

c) The nature of electrochemical corrosion: the redox process occurs on the surface of the electrodes. At the cathode, the oxidation of the metal occurs. At the positive electrode, the reduction of the ionic (if the electrolyte solution is acid)

3. Comparison between electrochemical corrosion and chemical erosion

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