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Hydrogen Sulfide Corrosion Mechanism
Hydrogen Sulfide Corrosion Mechanism
Hydrogen sulfide corrosion is the most important thing in the world for a long time due to the damage of various things. The study of its reasons is related to the safety of the work and the life of the utensils.
Properties of Hydrogen Sulfide
Hydrogen sulfide is also gas, which is colorless and smelly like rotten eggs, toxic and flammable. In water, it can gradually dissociate, generating hydrogen ions and hydrogen sulfide ions. This dissociation state is the foundation of corrosion.
The principle of electrochemical corrosion
1. ** Anodic reaction **: When the metal encounters hydrogen sulfide, the metal atom is prone to lose electrons, forming metal ions and dissolving into the medium. Taking iron as an example, the iron atom (Fe) loses two electrons and forms ferrous ions (Fe ² ²). This process is the oxidation reaction of the anode. The reaction formula is: Fe-2e → Fe ².
2. ** Cathodic reaction **: Hydrogen ions generated by hydrogen sulfide in water gain electrons at the cathode and turn into hydrogen atoms. Hydrogen atoms or two pairs combine to form hydrogen molecules to escape, or penetrate into the metal lattice. If hydrogen ions (H 🥰) gain electrons, the reaction formula is: 2H 🥰 + 2e → H 🥰; if it penetrates into the metal lattice, the state of this hydrogen atom is active, which is a hidden danger for subsequent corrosion.
Shape of hydrogen damage
1. Hydrogen Bubbling: Hydrogen atoms that penetrate into the metal are easily combined into hydrogen molecules in lattice defects, inclusions, etc. Hydrogen molecules accumulate in one place, generating huge internal pressure, causing bubbling on the metal surface. The rise of this bubbling damages the surface of the metal and weakens the strength of its structure.
2. ** Hydrogen-induced cracking **: When hydrogen accumulates in the metal to a certain extent, the internal stress of the metal increases greatly. In addition to the stress of the material itself, the two are superimposed, causing the metal to crack along the grain boundary or through the crystal. The cracks gradually expand and eventually cause the metal to crack, which is very harmful.
3. ** Sulfide stress corrosion cracking **: In the coexistence of tensile stress, hydrogen atoms generated by hydrogen sulfide penetrate into the metal, cooperate with stress, and accelerate the emergence and expansion of cracks. This corrosion cracking, often sudden and without warning, is a great risk in the chemical industry, oil and gas and other industries.
Influencing factors
1. ** Hydrogen sulfide concentration **: The higher the concentration, the more hydrogen ions and hydrogen sulfide ions are dissociated, and the faster the corrosion rate. However, when the concentration reaches a certain value, the increase in corrosion rate gradually slows down.
2. ** Temperature **: Moderate temperature rise, the reaction rate is accelerated, and the molecular motion intensifies. But if the temperature is too high, hydrogen sulfide escapes, and the corrosion rate may decrease.
3. ** Solution pH value **: When the pH value rises, the concentration of hydrogen ions decreases, the cathodic hydrogen evolution reaction is suppressed, and the corrosion rate also decreases.
Knowing the mechanism of hydrogen sulfide corrosion can be the basis for anti-corrosion, so as to ensure the safety of the workpiece and the smooth operation of the industry.
Hydrogen sulfide corrosion is the most important thing in the world for a long time due to the damage of various things. The study of its reasons is related to the safety of the work and the life of the utensils.
Properties of Hydrogen Sulfide
Hydrogen sulfide is also gas, which is colorless and smelly like rotten eggs, toxic and flammable. In water, it can gradually dissociate, generating hydrogen ions and hydrogen sulfide ions. This dissociation state is the foundation of corrosion.
The principle of electrochemical corrosion
1. ** Anodic reaction **: When the metal encounters hydrogen sulfide, the metal atom is prone to lose electrons, forming metal ions and dissolving into the medium. Taking iron as an example, the iron atom (Fe) loses two electrons and forms ferrous ions (Fe ² ²). This process is the oxidation reaction of the anode. The reaction formula is: Fe-2e → Fe ².
2. ** Cathodic reaction **: Hydrogen ions generated by hydrogen sulfide in water gain electrons at the cathode and turn into hydrogen atoms. Hydrogen atoms or two pairs combine to form hydrogen molecules to escape, or penetrate into the metal lattice. If hydrogen ions (H 🥰) gain electrons, the reaction formula is: 2H 🥰 + 2e → H 🥰; if it penetrates into the metal lattice, the state of this hydrogen atom is active, which is a hidden danger for subsequent corrosion.
Shape of hydrogen damage
1. Hydrogen Bubbling: Hydrogen atoms that penetrate into the metal are easily combined into hydrogen molecules in lattice defects, inclusions, etc. Hydrogen molecules accumulate in one place, generating huge internal pressure, causing bubbling on the metal surface. The rise of this bubbling damages the surface of the metal and weakens the strength of its structure.
2. ** Hydrogen-induced cracking **: When hydrogen accumulates in the metal to a certain extent, the internal stress of the metal increases greatly. In addition to the stress of the material itself, the two are superimposed, causing the metal to crack along the grain boundary or through the crystal. The cracks gradually expand and eventually cause the metal to crack, which is very harmful.
3. ** Sulfide stress corrosion cracking **: In the coexistence of tensile stress, hydrogen atoms generated by hydrogen sulfide penetrate into the metal, cooperate with stress, and accelerate the emergence and expansion of cracks. This corrosion cracking, often sudden and without warning, is a great risk in the chemical industry, oil and gas and other industries.
Influencing factors
1. ** Hydrogen sulfide concentration **: The higher the concentration, the more hydrogen ions and hydrogen sulfide ions are dissociated, and the faster the corrosion rate. However, when the concentration reaches a certain value, the increase in corrosion rate gradually slows down.
2. ** Temperature **: Moderate temperature rise, the reaction rate is accelerated, and the molecular motion intensifies. But if the temperature is too high, hydrogen sulfide escapes, and the corrosion rate may decrease.
3. ** Solution pH value **: When the pH value rises, the concentration of hydrogen ions decreases, the cathodic hydrogen evolution reaction is suppressed, and the corrosion rate also decreases.
Knowing the mechanism of hydrogen sulfide corrosion can be the basis for anti-corrosion, so as to ensure the safety of the workpiece and the smooth operation of the industry.
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