【Daily Question No. 315】November 17, 2018

Hydrogen sulfide reacts with iron in the system to form iron sulfide; the reaction equation is: Fe + H2S → FeS + H2↑. This forms a brittle, flaky scale that provides no protective effect, and it poses a serious threat to equipment and pipelines.

In the system, hydrogen sulfide reacts with iron to form iron sulfide; when its concentration is below 200–250, it causes no corrosion or only minimal corrosion to steel； When the temperature is above 260, corrosion accelerates, increasing steadily as the temperature rises; especially between 315 and 480, for every increase of 55, the corrosion rate doubles. The higher the H2S concentration and partial pressure, the more severe the corrosion; the corrosion rate reaches its maximum when the volume concentration of hydrogen sulfide exceeds 1%. The corrosion caused by wet hydrogen sulfide is mainly due to electrochemical corrosion and the diffusion of hydrogen atoms generated by reactions into the steel.

Stress corrosion also occurs alongside corrosion.

Hydrogen sulfide reacts with iron in the system to form iron sulfide. The reaction is as follows: Fe + H2S = FeS + H2. This is a type of rust that is brittle, prone to flaking off, and provides no protective layer; it poses a serious threat to reactors, heat exchangers, and high-pressure pipelines. The main factors affecting the corrosion rate of hydrogen sulfide are temperature and H2S concentration; when the temperature is below 200–250°C, hydrogen sulfide does not cause corrosion or only causes minimal corrosion to steel ； When the temperature is above 260°C, corrosion accelerates, increasing steadily as the temperature rises; especially in the range of 315–480°C, the corrosion rate doubles for every 55°C increase. The higher the H2S concentration and partial pressure, the more severe the corrosion; the corrosion rate reaches its maximum when the volume concentration of hydrogen sulfide exceeds 1%. In addition, substances such as water and acidic compounds also affect the corrosion caused by hydrogen sulfide; for example, in the presence of HCl, the reaction FeS + 2HCl → FeCl2 + H2S occurs. Among them, the impact of water is particularly severe. **The \"Regulations on Safety Inspection of Pressure Vessels\" issued by the Quality and Technical Supervision Bureau in 1999 provide the following definition for a wet hydrogen sulfide stress corrosion environment: ① Temperature ≤ (60 + 2P)°C, where P is the pressure in MPa (gauge pressure) ； ②The hydrogen sulfide partial pressure is ≥0.00035 MPa, which is equivalent to a solubility in room temperature water of ≥10 mg/L ； ③The medium contains liquid water or is below the dew point of water ； ④pH

It reacts with the wall of the vessel to produce iron oxide and ferrous oxide

Hydrogen sulfide reacts with iron in the system to form iron sulfide; the reaction equation is: Fe + H2S → FeS + H2↑. This forms a brittle, flaky layer of rust that provides no protective effect and poses a serious threat to equipment and pipelines.

Hydrogen sulfide corrosion refers to the corrosion that occurs in oil and gas pipelines due to the presence of a certain concentration of hydrogen sulfide (H2S) along with water. There are mainly two types: electrochemical corrosion and hydrogen-induced damage. When hydrogen sulfide (H2S) dissolves in water, it ionizes to become acidic, causing electrochemical corrosion of the pipes, which leads to thinning of the pipe walls or localized pitting and perforation. The hydrogen atoms generated during the corrosion process are absorbed by the steel and accumulate in the areas with metallurgical defects in the pipes, which can lead to the embrittlement of the steel, the initiation of cracks, and ultimately cracking.

Hydrogen sulfide reacts with iron in the system to form iron sulfide. The reaction is as follows: Fe + H2S = FeS + H2. This is a type of rust that is brittle, prone to flaking off, and provides no protective layer; it poses a serious threat to reactors, heat exchangers, and high-pressure pipelines. The main factors affecting the corrosion rate of hydrogen sulfide are temperature and H2S concentration; when the temperature is below 200–250°C, hydrogen sulfide does not cause corrosion or only causes minimal corrosion to steel ； When the temperature is above 260°C, corrosion accelerates, increasing steadily as the temperature rises; especially in the range of 315–480°C, the corrosion rate doubles for every 55°C increase. The higher the H2S concentration and partial pressure, the more severe the corrosion; the corrosion rate reaches its maximum when the volume concentration of hydrogen sulfide exceeds 1%. In addition, substances such as water and acidic compounds also affect the corrosion caused by hydrogen sulfide; for example, in the presence of HCl, the reaction FeS + 2HCl → FeCl2 + H2S occurs.

Hydrogen sulfide is an inevitable gas component in the hydrogenation process; in addition to H2S being generated from the sulfides present in the feedstock through hydrogenation, DMDS also needs to be added during pre-sulfurization. Part of this sulfur reacts with the catalyst, while the excess forms H2S. To maintain the catalyst’s activity, it is also necessary to keep a certain concentration of H2S in the recycle gas; therefore, hydrogen sulfide corrosion is an issue that cannot be ignored, as hydrogen sulfide reacts with iron in the system to form iron sulfide. The reaction is as follows: Fe + H2S = FeS + H2. This is a type of rust that is brittle, prone to flaking off, and provides no protective layer; it poses a serious threat to reactors, heat exchangers, and high-pressure pipelines. The main factors affecting the corrosion rate of hydrogen sulfide are temperature and H2S concentration; when the temperature is below 200–250°C, hydrogen sulfide does not cause corrosion or only causes minimal corrosion to steel ； When the temperature is above 260°C, corrosion accelerates, increasing steadily as the temperature rises; especially in the range of 315–480°C, the corrosion rate doubles for every 55°C increase. The higher the H2S concentration and partial pressure, the more severe the corrosion; the corrosion rate reaches its maximum when the volume concentration of hydrogen sulfide exceeds 1%. In addition, substances such as water and acidic compounds also affect the corrosion caused by hydrogen sulfide; for example, in the presence of HCl, the reaction FeS + 2HCl → FeCl2 + H2S occurs. Among them, the impact of water is particularly severe. **The \"Regulations on Safety Inspection of Pressure Vessels\" issued by the Quality and Technical Supervision Bureau in 1999 provide the following definition for a wet hydrogen sulfide stress corrosion environment: ① Temperature ≤ (60 + 2P)°C, where P is the pressure in MPa (gauge pressure) ； ②The hydrogen sulfide partial pressure is ≥0.00035 MPa, which is equivalent to a solubility in room temperature water of ≥10 mg/L ； ③The medium contains liquid water or is below the dew point of water ； ④pH

Hydrogen sulfide reacts with iron in the system