Sacrifice anode cathodic protection

A method of protecting the protected metal by using the protected metal as the cathode and a specific material as the auxiliary anode. However, in terms of its protection effect and investment, it is recommended to protect the whole large tank farm and buried pipe network. Impressed current cathodic protection is a cathodic polarization of the protected metal by passing a cathodic current through an applied DC source.

(4) During operation, the maintenance work is simple. Cathodic protection is divided into sacrificial anode protection and forced current protection. The following two methods are introduced respectively. These metal structures are in direct or indirect contact with the soil through the coating.

Protection potential refers to the potential required by cathodic protection to make metal erosion rest (or negligible).

* Cathodic protection control system

Anodic ground beds are generally divided into shallow buried anodic ground beds and deep well anodic ground beds. Whether the site is suitable for deep well protection also needs to consider the local geology, stratigraphic structure and the distribution of nearby metal structures.

Deep well anode cathodic protection is a kind of cathodic protection method emerging in recent years. The anode used is basically the same as the shallow buried one, but the construction is much more complicated than the shallow buried one, and the one time investment is relatively high, and the debugging is more troublesome.

3. High current efficiency. Materials commonly used as sacrificial anodes include magnesium and magnesium alloys, zinc alloys, aluminum alloys, etc. It has been widely used in the protection of ships, steel pile wharfs, circulating pumps, condensers and seawater pipelines. In order to ensure the control and detection of the impressed current system, a seawater Ag/AgCl composite reference electrode with high purity zinc was developed. However, in terms of its protection effect and investment, it is recommended to protect the whole large tank farm and buried pipe network. Compared with conventional auxiliary anodes, flexible anodes have superior performance in the following fields:

Flexible anode, also known as cable anode, is a new type of anode. In the early stage, it was mainly developed to solve the problem of cathodic protection of aging pipelines with aging cover layer. Now, it has been widely used in the protection of new and existing pipelines and storage tanks. Magnesium anode is used in fresh water and soil with high resistivity, zinc anode is mostly used in soil with low resistivity and sea water, aluminum anode is mainly used in sea water, sea mud and crude oil storage tank sewage media.

4) There is no need for insulation between the storage tank and the pipeline, and no need to make any transformation to the electrical and lightning protection grounding system.

6. Cheap price and easy source.

A method of polarizing the protected body to reduce the rate by connecting the protected metal to a metal and alloy (i.e., a sacrificial anode) that can provide cathodic protection current. In general, soil erosion reduces the service life of metal structures to varying degrees.

(3) When construction together with pipeline installation, the amount of work is small

(2) The anode output current is small, and the possibility of cathode stripping is small

(1) A wide range of use, especially for medium and short intervals and complex pipe networks

The main features of sacrificial anode protection are:

In the earth battery formed by the protected metal and the sacrificial anode, the protected metal body is the cathode, and the potential of the sacrificial anode is often negative than that of the protected metal body. In the protective battery, it is the anode, which is eroded and consumed, so it is called the "sacrificial" anode.

The role of the auxiliary anode is to transfer the DC current output from the DC power supply from the medium to the metal structure to be protected. In engineering, the commonly used reference electrodes are copper/saturated copper sulfate, silver/silver halide and zinc reference electrodes, etc., these reference electrodes have their own characteristics, combined for different occasions.

3. High current efficiency.

Impressed current cathodic protection is to provide the required protection current by an applied power source. This method is mainly used to protect large or metal structures in high soil resistivity soils.

Cathodic protection of pipes in casing

In order to ensure that the cathodic protection current does not leak to the unprotected metal section, insulation joints are arranged at both ends of the long distance transmission pipeline.

* Anodic ground bed

3. Composition of forced current cathodic protection system

(5) Easy to achieve remote automatic monitoring

(4) Maintenance by professional staff is required during operation

(3) The installation work is small, and cathodic protection can be added to the old pipeline

(2) The output current is large, and the one-time investment is relatively small

(1) It is used for the protection of long distance transmission pipelines and regional pipe networks

The main features of forced current protection are:

A method of connecting a protected metal to a negative impressed current and providing a protective current from an external source to reduce the rate of erosion.

Deep well anode cathodic protection is a kind of cathodic protection method emerging in recent years. The anode used is basically the same as the shallow buried one, but the construction is much more complicated than the shallow buried one, and the one time investment is relatively high, and the debugging is more troublesome. In practice, the protective potential of steel is usually -0.85V(CSE), that is, when the metal is at a more negative potential than -0.85V(CSE), the metal is protected and erosion can be ignored. The mesh anode is an auxiliary anode for impressed current cathodic protection which is composed of a mixed metal oxide strip anode and a titanium metal joint.

6. Cheap price and easy source. In order to ensure the control and detection of the impressed current system, a seawater Ag/AgCl composite reference electrode with high purity zinc was developed. Forced current protection of the main equipment, potentiostat, auxiliary anode, reference electrode.

Corrosion prevention technology of buried steel structure

⑤ High resistivity environment. In addition, unequal erosion of metal structures will occur under different conditions, which will cause local perforation for pipelines, and greatly affect the service life of the entire pipeline.

3) No packing, simple installation, easy quality assurance. In order to protect the rolling structure of the ship's shaft and propeller well, the shaft grounding device should be installed. The discharge anode group must be set according to the influence of stray current in the parallel section between long distance pipeline and high voltage transmission line or the parallel section crossing with electrified railway. Generally, when the working condition of the structure to be protected (such as the immersed area, water quality, etc.) is basically unchanged or changes very little, you can use the manually controlled rectifier; But when the working condition of the structure is often changing, the potentiostat should be used automatically to make the potential of the structure always in the best protection range.

2) Basically no stray current is generated, which will not cause erosion interference to other structures. At present, there are two widely used rectifier and potentiostat.

Reference electrode

I have done a lot of work in the research and development of auxiliary anode materials. The developed platinum-niobium anode has the advantages of small volume, large discharge, long service life, reliable work and so on.

5) not easy to be damaged by future construction, long service life.

* Anodic ground bed

3. Composition of forced current cathodic protection system

(5) Easy to achieve remote automatic monitoring

(4) Maintenance by professional staff is required during operation

(3) The installation work is small, and cathodic protection can be added to the old pipeline

(2) The output current is large, and the one-time investment is relatively small

(1) It is used for the protection of long distance transmission pipelines and regional pipe networks

The main features of forced current protection are:

A method of connecting a protected metal to a negative impressed current and providing a protective current from an external source to reduce the rate of erosion. The anode mesh is pre-laid in the tank foundation to provide a protective current for the tank bottom plate. In engineering, the commonly used reference electrodes are copper/saturated copper sulfate, silver/silver halide and zinc reference electrodes, etc., these reference electrodes have their own characteristics, combined for different occasions. Transistor potentiostat output is stable, no noise, high control accuracy, but the circuit is more complex. It has been widely used in the protection of ships, steel pile wharfs, circulating pumps, condensers and seawater pipelines.

Dc power supply

Impressed current cathodic protection system consists of the following parts: (1) DC power supply, (2) auxiliary anode, (3) reference electrode.

5) not easy to be damaged by future construction, long service life. These materials have their own characteristics and are used in different situations.

* Cathodic protection insulation and electrical connection system

In accordance with the cathodic protection design code, if the construction period of the pipeline exceeds 6 months, the pipeline shall be equipped with a temporary cathodic protection system to avoid soil erosion before the applied current cathodic protection system is put into use.

In the corrosive medium, when the sacrificial anode forms an electrical connection with the protective body, the cathodic protection current is provided by the dissolution of the anode itself. The materials used as sacrificial anode generally have the following prerequisites:

Sacrificial anode

When the pipeline crosses the road or railway, steel casing is needed. Two cathode cables and two long-life solid copper sulfate reference electrodes for potential control are provided at the cathode galvanization point.

1) The current distribution is average and the output is adjustable to ensure the full protection of the storage tank. Soil acid and alkali, bacteria type and content, inorganic salt ion type and content, stray current size and direction are important factors affecting its erosion function, sometimes the soil erosion is very severe. Two cathode cables and two long-life solid copper sulfate reference electrodes for potential control are provided at the cathode galvanization point. As the anode material is consumed, the current released supplies the protected metal structure and polarizes the cathode, thus achieving protection. In addition, in order to make the anode output protection current more average, to avoid the structure around the anode produced over protection, sometimes near the anode also must be coated with anode shielding layer. At present, there are two widely used rectifier and potentiostat.

In an impressed current cathodic protection system, an uninterrupted DC power supply is required to provide the protection current.

The role of the auxiliary anode is to transfer the DC current output from the DC power supply from the medium to the metal structure to be protected.

3) No packing, simple installation, easy quality assurance. SCR potentiostat has large power and small volume, but its overload capacity is not strong.

1. Sacrificial anode method

There are various kinds of buried metal structures, including metal pipes and pipe networks for conveying various fluids, metal storage tanks, and lightning protection grounding devices (nets), etc. Therefore, it is very necessary to effectively protect the buried metal structures. The existing solution is generally the combination of external coating and cathodic protection.

1) The current distribution is average and the output is adjustable to ensure the full protection of the storage tank.

In the corrosive medium, when the sacrificial anode forms an electrical connection with the protective body, the cathodic protection current is provided by the dissolution of the anode itself. The materials used as sacrificial anode generally have the following prerequisites:

Sacrificial anode

When the pipeline crosses the road or railway, steel casing is needed. In order to protect the rolling structure of the ship's shaft and propeller well, the shaft grounding device should be installed.

Cathodic protection

.

1. It has enough negative potential and is not messy.

Cathodic protection of pipes in casing

In order to ensure that the cathodic protection current does not leak to the unprotected metal section, insulation joints are arranged at both ends of the long distance transmission pipeline.

5. Erosion products are non-toxic and do not pollute the environment.

Protection potential refers to the potential required by cathodic protection to make metal erosion rest (or negligible). Many materials can be used as auxiliary anodes, such as scrap steel, graphite, lead-silver alloy, high-silicon cast iron, platinum-coated titanium, platinum-coated niobium, and mixed metal oxide electrodes.

* Cathodic protection control system

Anodic ground beds are generally divided into shallow buried anodic ground beds and deep well anodic ground beds.

(4) long interval, small spacing parallel pipeline;

③ The outer wall of the tank bottom;

(2) the complex pipe network;

① The old pipe with aging cage cover;

The basic structure of the anode is copper core wrapped conductive polymer and acid and alkali resistant braiding layer, and then through the special process processing, so that it has the function of heat resistance, anti-aging, in the scope of working current, its working life is expected to reach more than 40 years. Compared with conventional auxiliary anodes, flexible anodes have superior performance in the following fields:

Flexible anode, also known as cable anode, is a new type of anode. In the early stage, it was mainly developed to solve the problem of cathodic protection of aging pipelines with aging cover layer. Now, it has been widely used in the protection of new and existing pipelines and storage tanks. Deep well anodes can also be used to protect long distance pipelines, but they are rarely used because of complex field construction.

2) Basically no stray current is generated, which will not cause erosion interference to other structures.

Cathodic protection is a kind of erosion prevention method based on electrochemical erosion principle. In this structure, the copper core ensures low longitudinal resistance and can carry current far; Moreover, the conductive polymer ensures that there is a high resistance ground across the copper core, so that the current in the copper core can only slowly "drip" into the ground.

Reference electrode

I have done a lot of work in the research and development of auxiliary anode materials. The developed platinum-niobium anode has the advantages of small volume, large discharge, long service life, reliable work and so on. The American Society of Erosion Engineers (NACE) defines cathodic protection as reducing the erosion rate by applying an applied electromotive force to shift the erosion current of the electrode towards a lower oxidizing potential. Magnesium anode is used in fresh water and soil with high resistivity, zinc anode is mostly used in soil with low resistivity and sea water, aluminum anode is mainly used in sea water, sea mud and crude oil storage tank sewage media. Therefore, it is very necessary to effectively protect the buried metal structures. The existing solution is generally the combination of external coating and cathodic protection.

4. High electrochemical equivalent. According to the data provided by a cathodic protection engineering company in The United States, cathodic protection is one of the most economical means to prevent corrosion of steel storage tanks from economic consideration. In order to ensure that the pipe in the casing is not corroded during the designed life, it is necessary to use bracelet type zinc anode or zinc band pole for cathodic protection. The American Society of Erosion Engineers (NACE) defines cathodic protection as reducing the erosion rate by applying an applied electromotive force to shift the erosion current of the electrode towards a lower oxidizing potential. Cathodic protection is divided into sacrificial anode protection and forced current protection. The following two methods are introduced respectively.

In an impressed current cathodic protection system, an uninterrupted DC power supply is required to provide the protection current.

The reference electrode has two functions: on the one hand, it is used to measure the potential of the protected structure and monitor the protection effect; On the other hand, the control signal is provided for the automatically controlled potentiostat to adjust the output current, so that the structure is always in a good state of protection. Impressed current cathodic protection is a cathodic polarization of the protected metal by passing a cathodic current through an applied DC source. Sacrificial anode Cathodic protection is the bonding or welding of a metal with a negative potential, such as aluminum, zinc, or magnesium, on a metal structure.

7) High cost performance, the cost is only one times of the current magnesium band sacrificial anode; Although the current is provided by the potentiostat for a long time, its reliability, life and comprehensive economic benefit are far higher than that of the sacrificial anode.

6) The buried depth is shallow, especially suitable for the storage tank built on the rock with thin backfill layer.

* Temporary protection system

Drain protection should be adopted for pipes in areas with strong stray current interference.

Impressed current cathodic protection products

At present, the sacrificial anodes of zinc base, aluminum base and magnesium base alloy are commonly used. Their material composition and electrochemical function are different, and the application environment is also different.

* Cathodic protection drainage system

The cathodic protection testing system is composed of potentiostat and pipeline testing pile. The potentiostat can automatically measure the potential of the energized point, the working potential and output current of the potentiostat. The pipeline test pile can detect the protection potential of the pipeline and the working potential, output current and open circuit potential of the sacrificial anode.

Cathodic protection is an effective method to control the erosion of steel storage tanks and pipelines. It can effectively compensate for the erosion caused by coating defects and greatly prolong the service life of the storage tanks and pipelines. In general, soil erosion reduces the service life of metal structures to varying degrees.

2. Forced current protection

(5) the anode output current can not be adjusted, and the controllability is small. The long life copper/copper sulfate reference electrode for cathodic protection of buried pipelines developed by us has been widely used because of its advantages such as reliable function and long service life. The external power supply will introduce the protection current into the ground through the buried auxiliary anode, and provide the protected metal through the soil. The protected metal is still the cathode in the earth battery, and only the reduction reaction occurs on its surface, and the oxidation reaction of metal ions will not occur again, so that the erosion is inhibited. Magnetic saturation potentiostat fastening durable, overload capacity is strong, but the volume is relatively large, processing technology is more complex.

The 2007-01-12 10:25:13 | classification: electrochemical | tags: cathodic protection | size medium subscription

Cathodic protection

The reference electrode has two functions: on the one hand, it is used to measure the potential of the protected structure and monitor the protection effect; On the other hand, the control signal is provided for the automatically controlled potentiostat to adjust the output current, so that the structure is always in a good state of protection. Many materials can be used as auxiliary anodes, such as scrap steel, graphite, lead-silver alloy, high-silicon cast iron, platinum-coated titanium, platinum-coated niobium, and mixed metal oxide electrodes. In order to ensure that the pipe in the casing is not corroded during the designed life, it is necessary to use bracelet type zinc anode or zinc band pole for cathodic protection.

5. Erosion products are non-toxic and do not pollute the environment. In addition, unequal erosion of metal structures will occur under different conditions, which will cause local perforation for pipelines, and greatly affect the service life of the entire pipeline.

Corrosion prevention technology of buried steel structure

⑤ High resistivity environment. Magnetic saturation potentiostat fastening durable, overload capacity is strong, but the volume is relatively large, processing technology is more complex. According to the data provided by a cathodic protection engineering company in The United States, cathodic protection is one of the most economical means to prevent corrosion of steel storage tanks from economic consideration.

Cathodic protection is a kind of erosion prevention method based on electrochemical erosion principle.

1. It has enough negative potential and is not messy. Generally, when the working condition of the structure to be protected (such as the immersed area, water quality, etc.) is basically unchanged or changes very little, you can use the manually controlled rectifier; But when the working condition of the structure is often changing, the potentiostat should be used automatically to make the potential of the structure always in the best protection range.

Impressed current cathodic protection products

At present, the sacrificial anodes of zinc base, aluminum base and magnesium base alloy are commonly used. Their material composition and electrochemical function are different, and the application environment is also different.

(3) When construction together with pipeline installation, the amount of work is small

(2) The anode output current is small, and the possibility of cathode stripping is small

(1) A wide range of use, especially for medium and short intervals and complex pipe networks

The main features of sacrificial anode protection are:

In the earth battery formed by the protected metal and the sacrificial anode, the protected metal body is the cathode, and the potential of the sacrificial anode is often negative than that of the protected metal body. In the protective battery, it is the anode, which is eroded and consumed, so it is called the "sacrificial" anode. Soil is a complex mixed system composed of three phases of solid, liquid and gas. The interaction of its structure, composition and other environmental factors makes soil erosion more complicated than other media.

2. The anode polarization rate is small, the solution is average, and the product can fall off automatically.

(4) long interval, small spacing parallel pipeline;

③ The outer wall of the tank bottom;

(2) the complex pipe network;

① The old pipe with aging cage cover;

The basic structure of the anode is copper core wrapped conductive polymer and acid and alkali resistant braiding layer, and then through the special process processing, so that it has the function of heat resistance, anti-aging, in the scope of working current, its working life is expected to reach more than 40 years. In addition, in order to make the anode output protection current more average, to avoid the structure around the anode produced over protection, sometimes near the anode also must be coated with anode shielding layer.

4) There is no need for insulation between the storage tank and the pipeline, and no need to make any transformation to the electrical and lightning protection grounding system. A method of protecting the protected metal by using the protected metal as the cathode and a specific material as the auxiliary anode.

Impressed current cathodic protection is to provide the required protection current by an applied power source.

1. Sacrificial anode method

There are various kinds of buried metal structures, including metal pipes and pipe networks for conveying various fluids, metal storage tanks, and lightning protection grounding devices (nets), etc. As the anode material is consumed, the current released supplies the protected metal structure and polarizes the cathode, thus achieving protection. This method is mainly used to protect large or metal structures in high soil resistivity soils.

* Cathodic protection detection system

The control system of cathodic protection is composed of potentiostat, control box, anode ground bed and cathode galvanic point. The anode ground bed is connected to the anode contact of the potentiostat through a bus-current cable. Deep well anodes can also be used to protect long distance pipelines, but they are rarely used because of complex field construction. Forced current protection of the main equipment, potentiostat, auxiliary anode, reference electrode. Sacrificial anode Cathodic protection is the bonding or welding of a metal with a negative potential, such as aluminum, zinc, or magnesium, on a metal structure.

* Temporary protection system

Drain protection should be adopted for pipes in areas with strong stray current interference.

Auxiliary anode

There are three kinds of potentiostat widely used in engineering: SCR potentiostat, magnetic saturation potentiostat and transistor potentiostat. The mesh anode is an auxiliary anode for impressed current cathodic protection which is composed of a mixed metal oxide strip anode and a titanium metal joint.

4. High electrochemical equivalent.

Cathodic protection is an effective method to control the erosion of steel storage tanks and pipelines. It can effectively compensate for the erosion caused by coating defects and greatly prolong the service life of the storage tanks and pipelines. In this structure, the copper core ensures low longitudinal resistance and can carry current far; Moreover, the conductive polymer ensures that there is a high resistance ground across the copper core, so that the current in the copper core can only slowly "drip" into the ground. The external power supply will introduce the protection current into the ground through the buried auxiliary anode, and provide the protected metal through the soil. The protected metal is still the cathode in the earth battery, and only the reduction reaction occurs on its surface, and the oxidation reaction of metal ions will not occur again, so that the erosion is inhibited.

A method of polarizing the protected body to reduce the rate by connecting the protected metal to a metal and alloy (i.e., a sacrificial anode) that can provide cathodic protection current.

The network anode protection system has the following advantages over other cathodic protection methods:

The network anode cathodic protection method is a popular and mature new cathodic protection method for the outer wall of the bottom of newly-built storage tank. It has been widely used both at home and abroad.

Dc power supply

Impressed current cathodic protection system consists of the following parts: (1) DC power supply, (2) auxiliary anode, (3) reference electrode.

7) High cost performance, the cost is only one times of the current magnesium band sacrificial anode; Although the current is provided by the potentiostat for a long time, its reliability, life and comprehensive economic benefit are far higher than that of the sacrificial anode.

6) The buried depth is shallow, especially suitable for the storage tank built on the rock with thin backfill layer. The anode mesh is pre-laid in the tank foundation to provide a protective current for the tank bottom plate. The discharge anode group must be set according to the influence of stray current in the parallel section between long distance pipeline and high voltage transmission line or the parallel section crossing with electrified railway. Materials commonly used as sacrificial anodes include magnesium and magnesium alloys, zinc alloys, aluminum alloys, etc.

2. Forced current protection

(5) the anode output current can not be adjusted, and the controllability is small. The long life copper/copper sulfate reference electrode for cathodic protection of buried pipelines developed by us has been widely used because of its advantages such as reliable function and long service life. These metal structures are in direct or indirect contact with the soil through the coating.

2. The anode polarization rate is small, the solution is average, and the product can fall off automatically.

The network anode protection system has the following advantages over other cathodic protection methods:

The network anode cathodic protection method is a popular and mature new cathodic protection method for the outer wall of the bottom of newly-built storage tank. It has been widely used both at home and abroad.

* Cathodic protection insulation and electrical connection system

In accordance with the cathodic protection design code, if the construction period of the pipeline exceeds 6 months, the pipeline shall be equipped with a temporary cathodic protection system to avoid soil erosion before the applied current cathodic protection system is put into use. SCR potentiostat has large power and small volume, but its overload capacity is not strong. Soil acid and alkali, bacteria type and content, inorganic salt ion type and content, stray current size and direction are important factors affecting its erosion function, sometimes the soil erosion is very severe.

* Cathodic protection drainage system

The cathodic protection testing system is composed of potentiostat and pipeline testing pile. The potentiostat can automatically measure the potential of the energized point, the working potential and output current of the potentiostat. The pipeline test pile can detect the protection potential of the pipeline and the working potential, output current and open circuit potential of the sacrificial anode.

Auxiliary anode

There are three kinds of potentiostat widely used in engineering: SCR potentiostat, magnetic saturation potentiostat and transistor potentiostat.

* Cathodic protection detection system

The control system of cathodic protection is composed of potentiostat, control box, anode ground bed and cathode galvanic point. The anode ground bed is connected to the anode contact of the potentiostat through a bus-current cable. Soil is a complex mixed system composed of three phases of solid, liquid and gas. The interaction of its structure, composition and other environmental factors makes soil erosion more complicated than other media. Whether the site is suitable for deep well protection also needs to consider the local geology, stratigraphic structure and the distribution of nearby metal structures. Transistor potentiostat output is stable, no noise, high control accuracy, but the circuit is more complex. In practice, the protective potential of steel is usually -0.85V(CSE), that is, when the metal is at a more negative potential than -0.85V(CSE), the metal is protected and erosion can be ignored.

(4) During operation, the maintenance work is simple. These materials have their own characteristics and are used in different situations.