Ask for the corrosion mechanism and solution of steel corrosion, especially hydrogen sulfide and car

1.Definition of wet hydrogen sulfide environment.

1) International definition of wet hydrogen sulfide environment.

American Society of Corrosion Engineers (NACE) MR0175-97 "Sulfide Stress Cracking Resistant Metallic Materials for Oilfield Equipment" standard:

Sour gas system: total gas pressure, and H2S partial pressure;

Acidic multiphase system: when there are two-phase or three-phase media (oil, water, gas) in the ** process, the conditions can be relaxed as: total pressure of gas phase and partial pressure of H2S; When the gas phase pressure and H2S partial pressure ; or the gas phase H2S content exceeds 15%.

2) Definition of the domestic wet hydrogen sulfide environment.

In an environment where water and hydrogen sulfide are present at the same time, when the partial pressure of hydrogen sulfide is greater than or equal to MPa, or in liquefied petroleum gas where water and hydrogen sulfide are present at the same time, when the hydrogen sulfide content of the liquid phase is greater than or equal to 10 10-6, it is called a wet hydrogen sulfide environment".

3) Ionization of hydrogen sulfide.

In a wet hydrogen sulfide environment, hydrogen sulfide ionizes to make water acidic, and the dissociation reaction formula of hydrogen sulfide in water is:

h2s ＝ h+ ＋hs－ （1）

hs－ ＝h+ ＋s2－ （2）

2.Hydrogen sulfide electrochemical corrosion process.

Anode: Fe-2e Fe2+

Cathode: 2h+ +2e had + had 2h h2

h] diffusion in steel.

Where: HAD - Hydrogen atoms adsorbed on the surface of the steel [H] - Diffused hydrogen in the steel.

Anode reaction product: Fe2 S2 Fes

Note: The final product of the anode after the steel is corroded by hydrogen sulfide is ferrous sulfide, which is usually a defective structure, which has poor adhesion to the surface of steel, easy to fall off, easy to oxidize, and has a positive potential, so as the cathode and the steel matrix constitute an active microbattery, and the steel matrix continues to corrode.

1 Why can't oxygen oxidize iron to ferric ions in electrochemical corrosion of steel? Can iron only be oxidized to bivalent in galvanic cell reactions? The oxidizing capacity of oxygen is not enough to oxidize iron to trivalent, but if it is not a corrosion reaction, but another galvanic cell reaction, the iron can be oxidized to trivalent 2 with a suitable oxidant

In the galvanic corrosion of steel, there should be a layer of ferrous hydroxide attached to the surface of the iron, will this layer of ferrous hydroxide affect the continuation of the galvanic cell reaction? Ferrous hydroxide is unstable and reacts with water and oxygen in the air to form iron hydroxide, which then decomposes into iron oxide and water. The iron oxide produced by such a corrosion reaction will be relatively loose, so it will not affect the continuation of the reaction.

Hello! The most annoying thing about hydrogen sulfide in biogas is that it smells and corrodes the cooktop. If you don't call these two points, you can also use them.

Hydrogen sulfide ionizes in aqueous solution to form H+, which accelerates the hydrogen release of hydrogen ions due to the presence of H1, S2- and FeS, and accelerates the adsorption of H+ on the metal surface and then enters the metal lattice, encountering inclusions in the metal. When intergranular voids or other defects, atomic hydrogen accumulates and combines into molecular hydrogen in some parts, and the volume increases many times (more than 20 times), which produces great stress inside the metal, resulting in hydrogen bubbling or stepped cracks in low-strength low-alloy steel without being subjected to external stress, and causing high-strength or hardness steel to produce lattice deformation, making the lattice brittle and producing micro-cracks, that is, hydrogen embrittlement. This situation often leads to engineering accidents in the course of operations. Destroying our underground equipment, the hydrogen embrittlement effect is weakened above 80 degrees Celsius, so the hydrogen sulfide prevention of underground equipment during the construction process is generally above 2500 meters.

If desulfurization is not done, sulfur in the equipment will produce oxidation, hydrogen embrittlement, and internal stresses that can quickly damage the power generation equipment.

The most annoying thing about hydrogen sulfide in biogas is that it smells and corrodes the cooktop. If you don't call these two points, you can also use them.

Under the medium of hydrogen sulfide, a "dark film" (Cu2O oxide film) is formed on the surface of copper and copper alloys, which is brittle and cracks under tensile stress. The dark film on pure copper breaks on the grain, and the dark film on brass breaks at the grain boundary.

The hydrogen sulfide gas corrosion test chamber is used to test the corrosive effect of corrosive gas on materials.

Test Principle:Several gases such as SO2, H2S, NO2, Cl2, and O3 are used to accelerate the corrosion of materials or products in an environment of a certain temperature and relative humidity, and reproduce the degree of damage suffered by materials or products within a certain time range.

Test Criteria:gb/t

gb/t