Explain oxygen absorption corrosion in detail, what is oxygen absorption corrosion?

Oxygen absorption corrosion The electrochemical corrosion of the metal in the air when the oxygen in the air is dissolved in the water film on the surface of the metal in a very acidic or neutral solution is called oxygen absorption corrosion

For example, the corrosion of steel in moist air that is close to neutral is oxygen absorption corrosion, and its electrode reaction is as follows:

Negative electrode (Fe): Fe-2e = Fe2+

Positive electrode (C): 2H2O + O2 + 4E = 4oh-

The galvanic corrosion of metals such as steel is mainly oxygen absorption corrosion

When electrochemical corrosion occurs in a more acidic solution, hydrogen gas is released, and this corrosion is called hydrogen evolution corrosion. Carbon is generally found in steel products. In moist air, the surface of steel absorbs water vapor to form a thin film of water.

When carbon dioxide is dissolved in the water film, it becomes an electrolyte solution, which increases the H+ in the water. It is composed of countless tiny galvanic cells with iron as the negative electrode, carbon as the positive electrode, and acidic water film as the electrolyte solution. The redox reactions that occur in these galvanic cells are:

Negative electrode (iron): iron is oxidized fe-2e=fe2+; Positive electrode (carbon): H+ in solution is reduced to 2H++2E=H2

This results in a myriad of tiny galvanic cells. Finally, hydrogen is released on the surface of the carbon, and the iron is corroded, so it is called hydrogen evolution corrosion.

A type of galvanic corrosion.

In high school, it was about iron corrosion.

In neutral and weakly acidic media, the oxygen in the air will be dissolved in the water film on the surface of the metal and electrochemical corrosion will occur, and the galvanic corrosion of metals such as iron and steel is mainly oxygen absorption corrosion.

This corrosion characteristic is the formation of galvanic cells, the negative electrode is oxidized, which is the anode, and the positive electrode is reduced, which is the cathode.

Anode: 2Fe = 2Fe2+ +4E- Cathode: O2 + 2H2O + 4E- = 4Oh-

The corrosion of steel in near-neutral air is called oxygen absorption corrosion

Negative electrode (Fe): Fe - 2e = Fe2 Positive electrode (C): 2h o + o + 4e = 4oh Hydrogen gas is released from corrosion in a more acidic solution called hydrogen evolution corrosion

Negative electrode (Fe): Iron is oxidized Fe-2e = Fe2 Positive electrode (C): H + in solution is reduced 2H + 2e = h Dissolved oxygen is continuously reduced and consumed on the metal surface during the corrosion process.

Atmospheric oxygen first enters the solution through the air-solution interface, passes through the main liquid layer of the solution by convection and diffusion, and then reaches the cathode surface through the retention layer by diffusion.

The thickness of the retained layer on the surface of the cathode can reach 1 mm when the liquid is stationary, and the thickness is between when stirring. Oxygen can only diffuse in the retention layer, therefore, passing through the retention layer is the main resistance to oxygen transport to the cathode.

Hydrogen evolution corrosion occurs when the metal is acidic and the concentration of hydrogen ions is high, producing hydrogen, while oxygen absorption corrosion can occur under acidic, neutral and alkaline conditions, and is a reaction between the metal and the oxygen in the air.

The necessary conditions for the occurrence of violent oxygen absorption corrosion are known.

Yes: The potential of a metal is higher than that of a redox reaction.

The potential is low. The cathodic depolarizer for oxygen absorption corrosion is dissolved oxygen in solution. As corrosion progresses, oxygen is constantly depleted, and only oxygen from the air is used to replenish it.

Therefore, oxygen enters the solution from the air and migrates to the surface of the cathode cavity for mountain reduction reaction, and the slow oxidation of iron in moist air belongs to oxygen absorption corrosion, and the production of hydrogen in acid is hydrogen evolution corrosion.

Oxygen corrosion refers to the electrochemical corrosion of the metal in the weak acidic or neutral solution, and the oxygen in the air is dissolved in the water film on the surface of the metal.