Metal structure equipment for hydropower projects

Metal structure equipment for hydropower projects

Technical specification for corrosion prevention

Provisions that

1 around

This standard specifies the surface pretreatment, coating protection, thermal spraying metal protection, cathodic protection and corrosion protection standards and related technical requirements for metal structure equipment of hydropower and water conservancy projects.

This standard is applicable to the anti-corrosion design, construction, acceptance and management of metal structure equipment in hydropower projects.

2 Normative reference files

The following documents contain provisions which are referred to in this International Standard. All subsequent amendments (excluding errata) or revisions to dated referenced documents do not apply to this standard; however, parties to agreements under this Standard are encouraged to study the availability of the latest version of these documents. For undated references, the latest version applies to this standard.

GB/T 4948 aluminum - zinc - indium alloy sacrifice anode

GB/T 4950 zinc - aluminum - cadmium alloy sacrifice anode

GB/T 7387 Technical specifications for Marine reference electrodes

GB 8923 Steel surface rusting and derusting grades before coating

GB/T 9286 paint and varnish film marking test

GB 11375 Thermal spraying safety for metallic and other inorganic coatings

GB/T 13288 Evaluation of surface roughness grades of steel before coating (comparative sample method)

GB/T 17731 magnesium alloy sacrifice anode

GB/T 17848 Test method for electrochemical performance of sacrificedanodes

GB/T 17850 Technical requirements for non-metallic abrasive for spray cleaning of steel surfaces before coating

GB/T 18838 Technical requirements for metal abrasives for spray cleaning of steel surfaces before coating

3 Terms and Definitions

The following terms apply to this international Standard.

3.0.1

Surface preparation

In order to improve the adhesion between the coating and the matrix and the anti-corrosion effect, it is used before the coating

Mechanical or chemical treatment of the substrate surface to meet the requirements of coating

Shi.

3.0.2

Coating protection

A method of forming a solid coating on an object with a protective, decorative, or special function (e.g. insulation, corrosion protection, marking, etc.).

3.0.3

To protect the thermal spraying metal

The method of using heat source to melt, half-melt or soften metal material and spray it to the surface of matrix at a certain speed to form a coating.

3.0.4

2. cathodic protection

The technique of controlling the electrochemical corrosion of metals by cathodic polarization. Cathodic protection includes sacrificial anode method and forced current method.

3.0.5

Abrasive blast cleaning - abrasive

A solid material used for spray treatment of the substrate surface.

3.0.6

Clean the rust by air blast

Driven by compressed air, the process of purifying and coarsening the surface of the substrate by using the impact effect of high speed abrasive flow.

3.0.7

Cleaning the cleaning of handtools

The process of removing rust layer from the surface of matrix by hand tools.

3.0.8

Cleaning cleaning for power tools

The process of removing the rust layer from the surface of a substrate using a powered (pneumatic or electric) tool.

3.0.9

Adhesion adhesion

The strength of the bond between the film and the surface to be painted (through physical and chemical interactions).

3.0.10

Flame spraying

A thermal spraying method that uses the flame after mixing combustible gas and combustion supporting gas as the heat source.

3.0.11

Arc spraying arc spraying; electric spraying

The thermal spraying method uses the arc generated between two consumable electrode wires forming the coating material as the heat source, and the melting consumable electrode wires are added, and the compressed gas atomizes and ejects them onto the substrate to form the coating.

3.0.12

Coat sealer for thermal spraying

A material used to penetrate and seal pores in thermal sprayed metal coatings.

3.0.13

Minimum and partial thickness

The minimum of local thicknesses measured on the main surface of a work piece.

3.0.14

Bonding force

The strength of the bond between a thermal sprayed metal coating and the substrate.

3.0.15

-- The current is being forced

Also known as impressed current, the cathodic protection current is applied through an external power source.

3.0.16

Sacrificial anode

A metal or alloy that provides cathodic protection by increasing corrosion of its own.

3.0.17

The reference electrode is ejectrode

Self potential stable under the same measurement conditions, used to measure the electricity of other electrodes

The electrode of the position.

3.0.18

Maximum protection potential

The maximum absolute value of negative potential allowed under cathodic protection.

3.0.19

The IR drop IR drop

The voltage drop caused by resistance to a current flowing through a medium.

3.0.20

Stray current

To specify or design currents outside the loop.

3.0.21

Auxiliary anode is impressed current anode

The connection to the positive pole of a forced current source is limited to electricity for the purpose of providing current

Extremely.

3.0.22

Water connection resistance

Interface resistance of the anode in water in a cathodic protection system.

3.0.23

Natural potential

Corrosion potential of a metal in a medium without external current.

3.0.24

Working potential

When there is a protective current outflow, the potential of the anode is sacrificed.

3.0.25

Driving voltage

The difference between the working potential of the sacrificial anode and the polarized potential of the structure.

3.0.26

Practical current capability

The actual measured amount of electricity per unit mass consumed by the anode.

4. General regulation

4.0.1 Anti-corrosion measures shall be taken for metal structure equipment of hydropower projects (including steel gate, sewage barrier, hoist, pressure steel pipe and sewage cleaner, etc.).

4.0.2 The anti-corrosion design of metal structure equipment of hydropower and water conservancy shall be proposed simultaneously in the design of engineering structure. Anti-corrosion measures should be selected from the overall structure of the service life, maintenance difficulty, corrosion environment, the amount of investment and other factors. Anti-corrosion measures should be reasonable, advanced and economical.

4.0.3 Most of the metal structure equipment of hydropower and water conservancy projects are in the atmosphere, water level variation area and underwater area. Atmospheric area and water level variation area should be protected by coating or thermal spraying metal protection. Underwater areas can be protected by coating protection, thermal spraying metal protection, cathodic protection and coating (coating coating or thermal spraying metal layer) combined protection. The metal structure equipment in seawater and polluted media should be protected by cathodic protection and coating (coating or thermal spraying metal layer).

4.0.4 The structural form of metal structure equipment shall be as simple as possible, and the corrosion factors caused by design shall be avoided.

4.0.5 The anti-corrosion construction shall be completed by the contractor with the corresponding anti-corrosion construction qualification. Operators should be trained and have certificates.

4.0.6 The materials and equipment used in anti-corrosion engineering shall have product quality certificate or quality inspection report, which can be reinspected.

4.0.7 Process control should be strengthened in the construction of anti-corrosion engineering. Quality acceptance should be carried out before delivery and it can be put into use only after qualified quality.

4.0.8 The equipment and instruments used for quality inspection and testing shall be metrological verification according to the cycle, and shall be used within the specified validity period of verification.

4.0.9 At the time of completion and acceptance of anti-corrosion works, the following technical data shall be submitted: design documents and design change documents, factory certificates of materials and equipment, relevant inspection and testing reports, construction records, accident records, testing and inspection records, etc.

4.0.10 Anti-corrosion design, construction, acceptance and maintenance management shall not only comply with this standard, but also comply with the current relevant national standards or industry norms.

5 Surface pre processing

5.1 Generally

5.1.1 Surface pretreatment of metal structure equipment shall be carried out before coating and thermal spraying metal. Quality requirements for surface pretreatment shall be specified in the design documentation.

5.1.2 Surface pretreatment mainly includes degreasing purification and rust removal. Derusting is divided into jet derusting, hand tool derusting and power tool derusting.

5.1.3 Derusting quality inspection includes two indexes: surface cleanliness and surface roughness.

5.2 Surface pretreatment method

5.2.1 Degreasing purification

Before rust removal of metal structure equipment, welding slag, splash and other attachments should be carefully removed, and grease and other dirt visible on the surface should be cleaned according to one of the following methods.

1 solvent method. Use the solvent such as gasoline to scrub the surface, solvent and dishcloth to change often.

Alkaline cleaning agent method. With sodium hydroxide, sodium phosphate, sodium carbonate and sodium silicate solution scrub or spray cleaning, cleaning with clean fresh water fully rinse.

3 Emulsion cleaning method. Use emulsifying cleaning solution made of organic solution mixed with strong emulsion and wetting agent to clean, and rinse with clean fresh water after cleaning.

5.2.2 Spray derusting

Spray derusting is suitable for coating protection of metal structure equipment and surface pretreatment of thermal spraying metal protection.

1 requirements.

1) The surface cleanliness level after spray derusting shall not be lower than GB 8923

Fixed Sa2 grade, using thermal spray aluminum and aluminum alloy protection when the surface

The cleanliness level should reach Sa3.

2) The surface roughness value after spraying derusted should be selected according to the coating system, generally not more than one-third of the total thickness of the coating, and should be in the range of 40μm ~ lOOμm. The surface roughness values of different coating systems can be selected according to Table 5.2.2.

Table 5.2.2 Surface roughness requirements of different coating systems μm

Coating systems Conventional anticorrosive coatings heavy anticorrosive coatings thermal spray metal

Roughness Rz40 ~ 7060 ~ 100

60 ~ 100

Note: Rz refers to the height of the sum of the maximum profile peak height and maximum profile valley depth within the sampling length.

2 abrasive selection.

1) The abrasive used for spray derusting should be clean and dry. The abrasive type and particle size should be selected according to the original rust degree of the substrate surface, the rust removal method and the surface roughness required by the coating.

2) Metal abrasive shall comply with the provisions of GB/T18838.

3) Non-metallic abrasive shall comply with the provisions of GB/T 17850.

5.2.3 Manual and power tool derusting

Manual and power tool derusting is suitable for small or short service life metal structure equipment, as well as the local repair of coating defects and cannot be spray derusting, the surface cleanliness level shall be St3 specified in GB 8923.

5.3 Spray derusting construction

5.3.1 Jet derusting methods include dry and wet compressed air jet derusting.

5.3.2 Compressed air used for jet derusting shall pass through cooling device and oil-water separator

To deal with. The oil-water separator should be cleaned regularly.

5.3.3 The Angle between the spray direction and the normal line of the matrix metal surface should be 15° ~ 30°, and the distance between the nozzle and the matrix surface should be kept in the range of 100mm ~ 300mm. The nozzle hole

When the diameter increases by 25% due to wear, it should be replaced.

5.3.4 After rust removal, a vacuum cleaner or dry, oil-free compressed air should be used to remove dust and debris, and the cleaned surface should avoid re-pollution.

5.3.5 The surface that has been sprayed and derusted before coating should be kept dry. If rust returns, it should be treated again to meet the requirements of surface cleanliness.

5.3.6 spray derusting should be in the air relative humidity is less than 8596, substrate surface temperature is higher than the dew point at least 3 ℃ under the environmental conditions of work (except otherwise provided by the paint manufacturer), otherwise, effective measures should be taken, such as indoor homework or to heating surface, etc., in order to satisfy the requirement of the work environment, in the case of can't meet the above conditions should stop work. See Appendix A for the calculation method of dew point.

5.4 Quality Inspection

5.4.1 Surface cleanliness and surface roughness shall be checked after surface pretreatment, and the inspection shall be recorded.

5.4.2 The inspection of surface cleanliness and surface roughness shall be carried out under moderate lighting conditions.

5.4.3 When assessing the level of surface cleanliness, the surface under inspection shall be consistent with GB

For visual comparison evaluation of the corresponding standard sample or photograph in 8923. See Appendix B for surface cleanliness requirements.

5.4.4 The surface roughness can be evaluated visually according to the standard samples used in GB/T 13288

The roughness value of the standard comparison sample is shown in Appendix Co, or the roughness value is directly measured with a surface roughness meter. 5 points are measured within the length range of 40mm, and the arithmetic mean value is taken to evaluate the surface roughness value of the points.

6. Coating material protection

6.1 General demand

6.1.1 Coating protection Coating system design should be based on the use of metal structure equipment, service life, environmental conditions and economic factors such as comprehensive consideration.

6.1.2 The design of coating system shall include the selection of coating varieties, coating matching, coating thickness, surface pretreatment before coating and coating process, etc.

6.1.3 The design service life of the coating system shall be determined according to the service life, value and maintenance difficulty of the protected object. It is generally divided into short term of less than 5 years, medium term of 5 ~ 10 years and long term of 10 ~ 20 years.

6.1.4 The coating with excellent performance proved by engineering practice shall be selected, or the new coating with performance meeting the design requirements confirmed by test comparison or demonstration shall be selected.

6.2 Coating fitting and selection

6.2.1 Matching coatings

The coating (bottom layer, middle layer, surface layer) should have good matching and adhesion between layers. There should be no bottom biting phenomenon between the back coating and the front coating, and the thermal expansion coefficient of each coating should be the same or similar. See Table D.1 in Appendix D for coating adaptability between coatings.

6.2.2 Selection of coating system

L The metal structure equipment in the atmosphere should choose the coating system with good light aging resistance, salt fog erosion resistance, acid rain resistance and wet heat aging resistance according to the requirements of durability. Refer to Table E.1 to Table E.2 in Appendix E for selection.

2. The metal structure equipment in the water level variation area should choose the coating system with good performance of salt spray erosion resistance, light aging resistance, water erosion resistance, wet and heat aging resistance and dry and wet alternation according to the durability requirements. Refer to table F.l in Appendix F for selection.

3 metal structure equipment in the underwater area should be selected with good water resistance and biological erosion resistance coating system. Refer to Table F.2 in Appendix F for selection.

4 metal structure equipment with wear-resistant requirements, such as pressure steel pipe, sluice gate of spillway tunnel, etc., should choose heavy anticorrosion coating system with good abrasion resistance and water resistance, which can be selected according to table G.l in Appendix G.

For drinking water conveyance equipment, the coating system which is harmless to water quality and has good water resistance should be selected according to table H.1 in Appendix H.

6.3 Painting construction and quality control

6.3.1 Metal structure equipment should be coated with bottom coating in time after surface pretreatment.

6.3.2 The coating method shall be selected according to the physical properties of the coating, the construction conditions and the shape of the coated structure, and shall be carried out according to the requirements of the coating instructions. When brush coating, roll coating and spraying are feasible, the spraying method shall be given priority.

6.3.3 When both factory painting and site painting are feasible, factory painting should be preferred.

6.3.4 The coating shall not be carried out when the relative humidity is greater than 85% and the surface temperature of the coated substrate is lower than 3℃ dew point. If the paint manual has other provisions, should be in accordance with the requirements of the construction.

6.3.5 The surrounding environment shall be kept clean during the coating operation, so as to avoid the undried coating being polluted by dust and other pollutants.

6.3.6 Before coating, it is necessary to check the appearance quality of the coating and check whether there is crusty and irreversible precipitation on the coating surface.

6.3.7 Before coating, the surface pretreatment quality of the substrate shall be checked, and the coating can be carried out only after it is qualified.

6.3.8 The appearance of the preceding coating shall be inspected. If coating defects such as leakage, hanging and wrinkles are found, they shall be treated before the coating of the latter coating.

6.3.9 In the process of coating, wet film thickness measurement instrument should be used to measure the wet film thickness in time to control the dry film thickness of the coating.

6.3.10 Pay attention to the maintenance of the coating after coating. Before curing should avoid rain, exposure,

Trample, damaged coating should be timely use of the original coating coating repair.

6.3.11 Any changes in coating sites, methods and requirements shall be reported to the Owner and

The supervision engineer shall approve and record it.

6.3.12 The appearance of the coating shall be checked after the coating is finished. The surface of the coating should be uniform

Therefore, no flow, wrinkles, bubbles, pinholes, cracks and other defects.

6.4 Quality inspection

6.4.1 The following checks shall be carried out before painting:

Product specification, product batch number, qualification certificate and inspection data, physical performance index, process parameters, production date and storage period of the coating.

2. Requirements of coating on the pretreatment level of substrate surface, coating construction environment and coating method, etc.

3 the mixed ratio of multi-component coatings and the application time of the mixed coating instructions, additional instructions for special functional coatings, etc.

6.4.2 After the coating is cured and dried, use a non-destructive coating thickness tester to determine the thickness of the dry film. The thickness of more than 85% of the measuring points should meet the design requirements, and the minimum thickness should not be less than 85% of the design thickness. For coatings with maximum dry film thickness requirements, the relevant requirements shall be met.

6.4.3 Inspection of adhesion

Inspection of coating adhesion for field application should be carried out after the coating is completely cured. Delimiting method and pulling method adhesion inspection for damage inspection, such as on the workpiece, should be selected for non-important parts, repair as soon as possible after testing.

L Grid method.

1) The grid method is not applicable to the coating thickness of more than 250μm, also is not suitable

Used for textured coatings. See Appendix I for specific testing procedures.

2) Using 25mm width, adhesive force (10±1)N/25mm(or agreed)

The transparent pressure sensitive adhesive tape was used for adhesion inspection. Sampling, cutting tool and testing

For the requirements on boards, see GB/T 9286.

3) Result inspection should be carried out in a well-lit environment with normal or calibration

For passing vision, or by mutual agreement, magnification of 2 times is used

Or 3x visual magnifying glass carefully inspect the cut area of the test coating. in

During observation, turn the plate or change the direction of observation so that the test surface

Observation and illumination are not limited to one direction. Check the glue in a similar manner

Adhesive tape is also effective.

4) classify the test surface compared with the figure in table I.l in appendix I. right

The first three levels are valid for general purposes and may be used if assessed pass/fail.

5) If the test results are different, each test result shall be reported. In multichannel coating

In case of layer shedding, the site (between coatings or between coatings) should be reported

Between matrix surfaces).

2 the pull method.

1) Pull method is a quantitative test method of adhesion, suitable for different thickness

Coating, see Appendix J for specific operation steps.

2) The adhesion between the coating and the substrate surface shall be carried out as agreed by both parties.

6.4.4 Thick paste coating should use pinhole tester for pinhole inspection. If there is pinhole, it should be repaired after grinding.

7 Thermal spraying metal protection

7.1 General demand

7.1.1 Service life design of thermal spraying metal coating shall consider the service life and maintenance difficulty of metal structure equipment, which can be divided into long-term 10 ~ 20 years and super long-term 20 years or more.

7.1.2 The surface of thermal spraying metal coating shall be sealed with pore sealing agent, and coating shall be applied after sealing treatment.

7.1.3 The operation safety of thermal spraying shall meet the requirements of GB 11375.

7.2 Selection and requirements of metallic materials for thermal spraying

7. 2.1 Metal materials available for thermal spraying: zinc, aluminum, zinc alloy, aluminum alloy, etc.

7.2.2 Thermal spraying zinc, aluminum, zinc alloy, aluminum alloy should be selected for metal structure equipment in rural atmosphere and fresh water; thermal spraying aluminum, zinc alloy (zinc aluminum alloy) and aluminum alloy should be selected in Marine atmosphere, industrial atmosphere and seawater, as well as polluted fresh water.

7.2.3 Metal materials for thermal spraying shall meet the following requirements:

The zinc content in the zinc wire shall be greater than or equal to 99,99%;

Aluminum content of aluminum wire should be greater than or equal to 99.50%;

The content of zinc in zn-al alloy wire is generally between 84% and 86%, and the content of aluminum is 14%

~ l6%;

The allowable deviation of the metal content in the alloy is ±1% of the specified value unless otherwise specified.

Thermal spraying wire surface should be smooth, without corrosion products, burr, cracking, shrinkage,

There should be no foreign matter that will affect the properties of thermal spraying materials or coatings.

7.3 Selection of closing treatment and coating

7.3.1 Attention should be paid to metal coating when selecting sealing agent and coating for closed treatment

Compatibility between.

7.3.2 Epoxy can be used when the surface of thermal spraying metal coating is coated with epoxy coating

Zinc chromium yellow or zinc phosphate epoxy can be used as pore-sealing agent when polyurethane coatings are used. You can also choose diluted epoxy, polyurethane varnish or paint as a sealing agent. The seal f "should have small viscosity and easy penetration, and the dry film thickness should not be greater than 30μm.

7.3.3 The coating on the surface of the thermal spraying metal coating shall be selected according to the environment of the metal structure equipment and refer to 6.2 of this standard. The thickness of coating coating should be 60μm ~ 180μm, wear resistance requirements should be determined according to the grinding environment coating thickness.

7.4 Minimum local thickness of thermal spraying metal coating is recommended

The recommended minimum local thickness of thermal spraying zinc and aluminum coating in rural atmosphere, Marine atmosphere (industrial atmosphere), fresh water and seawater environment is shown in Table 7.4, and the minimum local thickness of thermal spraying zinc alloy and aluminum alloy coating can be selected by referring to Table 7.4.

Table 7.4 Recommended minimum local thickness of thermal spraying metal coating

environment

First maintenance life

Coating types

Minimum local thickness μm

Rural atmosphere

Ultra long Term (more than 20 years)

Thermal spray zinc 160

The thermal spraying anchor

160

Long term (10 ~ 20 years)

The thermal spraying zinc

120

The thermal spraying aluminum

120

Oceanic and atmospheric

(Industrial atmosphere)

Ultra long Term (more than 20 years)

Thermal spray zinc 200

The thermal spraying aluminum

160

Long term (10 ~ 20 years)

Thermal spray zinc 160

The thermal spraying anchor

120

Fresh water

Ultra long Term (more than 20 years)

Thermal spray zinc 200

The thermal spraying aluminum

160

Table 7.4 (continue)

environment

First maintenance life

Coating types

Minimum local thickness

Mu m

Fresh water

Long term (10 ~ 20 years)

Thermal spray zinc 160

The thermal spraying aluminum

120

The sea

Ultra long term (plus years)

Thermal spraying zinc 300

The thermal spraying aluminum

200

Long term (10 ~ 20 years)

The thermal spraying zinc

200

The thermal spraying aluminum

160

7.5 Requirements for thermal spraying

7.5.1 The ambient temperature of thermal spraying should be higher than 5 ° C or the surface temperature of the substrate should be at least 3 ° C higher than the dew point.

7.5.2 Thermal spraying should be carried out as soon as possible after pretreatment of the substrate surface. The maximum should not exceed 8h in general environment, and the maximum should not exceed 2H in wet and salt spray environment.

7. 5.3 The thickness of thermal spraying coating shall be uniform. Two or more layers of coating shall be constructed by vertical and cross method, and the thickness of a single layer shall not exceed 100μm.

7.5.4 Flame or arc spraying can be used for thermal spraying of zinc and zinc alloy, while arc spraying should be used for thermal spraying of aluminum and aluminum alloy.

7.5.5 After thermal spraying metal, sealing agent should be used for sealing treatment in time.

7.5.6 The construction requirements of coating shall be carried out in accordance with 6.3 of this standard.