Corrosion Coupon Holder Assembly

Corrosion Coupon Holder Assembly

For example, CC-P221-SR-6″-3″×1/2″×1/8″-MS1018-0-2

CC: Corrosion Coupons

P221: Solid Plug Body in 316LSS Viton O-Ring and PTFE Primary Packing

SR-6″: for assembling rectangular coupons and for 6″pipe

3″×1/2″×1/8″: Coupon Size

MS1018: Coupon Material

0: Finishing of Coupon is Mill

2: Material of Isolation Gasket is PTFE

Internal corrosion analysis of oil and gas pipelines

In recent years, due to the rapid economic development, oil and gas resources have been widely used, and the consumption of oil and gas resources is also increasing. Therefore, the pipeline required for oil and gas transportation has also increased sharply. At present, the internal corrosion of oil and gas gathering and transmission pipelines. Which are responsible for transportation and transportation, still exists in large quantities. Which seriously affects the transportation of oil and gas energy and the safe application in specific production and life. Therefore, it is necessary to strengthen the research on the internal corrosion of the gathering and transmission pipeline. To provide more possibilities for the realization of internal corrosion prevention. And to ensure the normal transportation and application of oil and gas energy.

1. Internal corrosion classification of oil and gas gathering and transportation pipeline

Crevice corrosion

Crevice corrosion is due to the contact between non-metallic materials and metallic materials. Because different metal materials or the same metal materials are in contact with each other. It is a common form of corrosion. So it is easy to appear under the rust layer on the inner wall of the pipeline and the weld porosity. In addition, the nut tightening surface and flange connection surface are prone to crevice corrosion. Crevice corrosion occurs mainly due to the accumulation of certain ions in the crevice, the change of acidity in the crevice, and the lack of oxygen molecules

Stress corrosion

Stress corrosion may be the residual stress in the metal of oil and gas gathering and transmission pipelines. Or the external stress of the gathering and transmission pipeline. It is a kind of corrosion fracture that occurs during the coexistence of a specific corrosion medium and tensile stress. The occurrence of residual stress is mainly caused by the following possible reasons:

• Firstly, it is caused by the volume change of pipe metal material.
• Secondly, it is caused by uneven cooling and cooling of pipe metal materials after heating.
• And then caused by deformation during processing and manufacturing.
• At last, it is caused by cold shrink fit, bolt tightening, and riveting.

Intergranular corrosion

Most oil and gas gathering and transmission pipelines are made of alloy materials. Intergranular corrosion often occurs at the grain boundaries of alloys. Once intergranular corrosion occurs, the elongation and strength of the pipeline will be greatly reduced. The mechanical strength also changed rapidly.

Pitting

Pitting is easy occurs in the local area of the inner wall of the oil and gas gathering and transmission pipeline. These pitting will make pits or caves expand to the inside. There may even be perforation here. Oil and gas gathering and transmission pipelines are prone to pit and pitting corrosion in soils with high chloride ion content. Generally, the maximum pitting depth, average pitting depth, and pitting density. And other indicators are used in the comprehensive evaluation of pitting.

Concentration difference battery corrosion

This is because the soil mass concentration near the inner wall metal surface of the oil and gas gathering and transmission pipeline is different. And this makes the electrode potential different, thereby forming concentration cell corrosion.

2. Causes of internal corrosion of oil and gas gathering and transmission pipeline

Corrosion caused by H2S

H2S dissociates HS – and S2 – and adsorbs on the metal surface. This forms an accelerated adsorption complex ion Fe (HS & # x2212;). The adsorbed HS -, S2 – causes the point displacement of the metal to a negative value. This thus promotes the acceleration of the cathode hydrogen evolution. The hydrogen atom is a strong depolarizer. So it is easy to obtain electrons at the cathode. At the same time, the strength of the metal bond between iron atoms is greatly weakened. Therefore, this further promotes the anodic dissolution reaction and makes the steel corrode

Corrosion caused by CO2

CO2 reacts with water to produce a certain amount of carbonic acid. Hydrogen ions ionized from carbonic acid can be directly reduced to precipitate hydrogen. At the same time, when the concentration of HCO3 ions on the metal surface is extremely low. H2O can also be reduced to precipitate hydrogen.

3. Specific measures for internal corrosion protection of oil and gas gathering and transmission pipeline

Coating technology

Coating anti-corrosion technology. Although, it is a common technical process in the anti-corrosion work of the outer wall of the pipeline. But it is also applicable to the anti-corrosion treatment of the inner wall of the pipeline. One of the key steps of coating is surface treatment. Before painting, we first use a grinder to polish the edges. At the same time, we will remove the potential oxide scale and delamination of welding. Special attention shall be paid to grinding or rounding welds, corners, sharp edges, etc. The welding slag in the gap shall be removed. If the relative humidity of the air is greater than 80% or the surface temperature is lower than the dew point by 3 ℃. The surface treatment shall be suspended.

Add corrosion inhibitor

Corrosion inhibitor is a kind of material that can effectively reduce the corrosion degree of the inner wall of the gathering and transmission pipeline. Based on the detailed study of the structure and trend of the pipeline system. According to the close relationship between corrosion inhibition effect and injection process, injection volume and cycle. Then we fill it into the pipeline reasonably. It can produce a corrosion inhibitor film in the corrosion area of the pipeline. This film isolates the inner wall of the pipeline from the corrosive gas. So that the occurrence of corrosion can be effectively reduced.

Crevice corrosion

Cathodic protection methods can be divided into the sacrificial anode method and the forced current method. When this method is adopted, due to the sealing characteristics of the gathering and transmission pipeline. Therefore, at the beginning of the design, we need to consider various factors in the implementation process. Such as the safety factors of oxygen and hydrogen generated during cathodic protection. The influence of temperature on the consumption rate of magnesium anode and the polarity reversal of zinc anode. The layout of the test system. Electrical insulation of the inner wall, etc.

4. Strengthening the prediction method of internal corrosion of oil and gas pipelines

Evaluation of pipeline internal corrosion based on Grey System Theory

Firstly, the advantage of the grey system in dealing with the problem of “small sample, poor information, and uncertainty” is used. Then for the limited pipeline internal corrosion database. Through the sequence generation, the corrosion influence law and the correlation degree of each factor are explored. So as to sort and analyze according to the correlation degree of each factor. Finally, the conclusion is drawn and the foundation is laid.

Prediction of pipeline internal corrosion based on flow field analysis

Because the calculation of corrosion rate has a great relationship with flow pattern division and relevant fluid parameters. Therefore, it is necessary to establish the flow field analysis model correctly. Then the flow field parameters are studied. Finally, the corrosion rate in the pipeline can be better predicted.

Evaluation of pipeline internal corrosion based on Fuzzy Mathematics

Fuzzy mathematics studies the problem of “cognitive uncertainty”. Its research object has the characteristics of “clear connotation and unclear extension”. According to the research status and progress of pipeline internal corrosion protection. Although the existing research has revealed the relevant mechanism to a certain extent. Moreover, she described the relationship between corrosion development and various factors of the medium. But there is still uncertainty between them. So based on this, we use the principle of fuzzy mathematics.

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