Bridge anti-corrosion design: basic principles/service life/anti-corrosion coating/color

1. Basic principles

The corrosion factors experienced by bridges vary depending on the environment they are in. Therefore, the anti-corrosion coating matching for bridge painting must follow the design concept of "tailor-made". Considering various factors in bridge painting, it is usually summarized as the following four basic principles of painting design.

1. Fully consider the corrosion environment in which the bridge is located

As mentioned in the previous section, based on the differences in atmospheric and chemical corrosion environments in which the bridge is located, ISO 12944-2:2017 "Paints and Varnishes" can be referred to Corrosion Protection of Steel Structures by Protective Coating Systems - Part 2: Environmental Classification "Standard and GB/T 15957-1995 "Classification of Corrosivity in Atmospheric Environment" classifies the corrosion environment in which bridges are located.

2. Fully consider the differences in the structure and working conditions of the bridge, as well as the differences in bridge structure, shape, and working conditions

There are significant differences in the requirements for Surface Treatment and painting operations, which are important criteria for tailored painting design. These factors mainly include:

Steel structure or concrete structure;

Bridge structure types - steel box girder, steel plate girder, steel truss girder, steel pipe arch;

The special characteristics of cables and wind nozzles in suspension bridges, cable-stayed bridges, and arch bridges;

The working conditions and environmental characteristics of each part in the bridge structure;

Requirements for bridge appearance and color design;

The connection between bridge manufacturing process and painting operation.

3. Fully consider the level of construction technology

The protective functions of coatings include cathodic protection, corrosion inhibition, and shielding. The construction process directly affects the surface treatment of the substrate and the film-forming quality of the coating, thereby affecting the protective function of the coating. For example, Rich Zinc paint applied to the Surface The treatment cannot reach the Sa2.5 grade steel surface and cannot achieve satisfactory cathodic protection effect. Therefore, modern bridge painting places special emphasis on the surface of the substrate Treat, select high-quality heavy-duty anti-corrosion coatings, design the coating matching correctly, strictly control the construction quality on site, strengthen maintenance and upkeep during operation, thereby ensuring and extending the service life of the bridge.

4. Fully consider investment restrictive factors

Painting design, like any design, must adhere to the "Life Cycle Economic Analysis" (LCCA) design philosophy (as described in Section 2 of this chapter); Controlling investment within permissible limits is feasible.

2. Service life of anti-corrosion coating

Select high-quality heavy-duty anti-corrosion coating system based on the expected service life of bridge anti-corrosion. Generally speaking, under the premise of meeting the quality standards for painting construction and conducting normal maintenance and upkeep of the coating after the completion and opening of the bridge, At present, it is generally believed internationally that the effective service life of protective coating for large newly-built steel structure bridges can reach 25 years. In China, there are some designs for protective coating for large newly-built bridges with effective service life Life requires a lifespan of 25-30 years. In recent years, the newly released ISO12944-1:2017 has clearly stated that the maximum durability protection period of the anti-corrosion coating system for steel structures is more than 25 years, which has promoted the design protection period of the anti-corrosion coating system for new bridges to higher requirements from the source of the standard.

3. Content of anti-corrosion coating design

The anti-corrosion coating design document should mainly include the following contents:

1. Coating design lifespan

Determine the coating life of the designed object;

2. Corrosion environment analysis

Analyze the corrosion environment (C1~C5, CX, Im1, etc.) of the designed object according to the requirements of ISO 12944-2:2017 and GB/T 15957-1995 standards;

3. Reference standards

Including relevant standards such as ISO 12944-2017, Q/CR 749-2020, JT/T 722-2021, and HG/T 3668-2009;

4. Supporting system

According to Thoroughly spray rust removal to Sa2.5 level (ISO) 8501-1:2007), when observed without magnification, the surface should be free of visible oil, grease, and dirt, and there should be no oxide scale, rust, coating, or foreign impurities. Any residual traces of pollutants should only appear as slight color spots in the form of dots or stripes. Painting area, search for relevant standards to design the coating system;

5. Product Technical Specifications

Based on the designed coating system, search for relevant standards to determine the various technical performance indicators for coating application;

6. Coating process plan

Usually includes structural treatment, surface treatment, surface cleaning, environmental inspection, and painting operations. Suggestions for structural treatment of interior bridge structures Structural treatment of surface defects, including sharp edges, corners, and other structural treatments; Surface Treatment mainly includes methods such as shot blasting, sandblasting, mechanical or manual polishing, acid washing, etc., to treat the surface of bridge structures; Surface cleaning mainly includes dust removal, oil and grease removal, surface salt removal, etc; Environmental inspection refers to the examination of the painting construction environment, including factors such as steel plate temperature, ambient temperature, relative humidity, dew point, ventilation, lighting, safety, etc; Painting operation refers to the selection of painting methods and various painting conditions according to the requirements of the painting process plan;

7. Quality inspection and acceptance

According to the requirements of the anti-corrosion coating design document, conduct quality inspections before and after coating, including checking surface roughness and cleanliness before coating, as well as checking coating thickness and tensile strength after coating, to complete quality inspection and acceptance.

4. Bridge coating color design

Nowadays, bridges are no longer just a tool for convenient transportation in the traditional sense. Many times, bridges represent the image and reflect the characteristics of a city. The steel box girder of Runyang Yangtze River Highway Bridge is made of metallic aluminum color, spanning thousands of miles of the Yangtze River, like a galaxy falling into the human world; The diagonal cables of Shantou Qishi Bridge are ingeniously selected in orange yellow, which looks like thousands of rays of rosy clouds pouring on the green waves from afar; The Xiaowan Bridge in Yunnan adopts an ice gray color that harmonizes with the natural colors of the surrounding green mountains and rivers, adding to the tourism and viewing experience. So bridges have become beautiful scenery lines in cities or regions. Therefore, while demanding the anti-corrosion performance of bridges, owners are increasingly concerned about the appearance of bridges, especially the color selection of anti-corrosion coatings.

However, designing colors is not an easy task either. Firstly, human perception of color is very complex. Some colors can make people feel peaceful and comfortable; On the contrary, some colors can make people restless and nervous. For people driving on bridges, color is also related to safety. Secondly, Color also has a significant impact on the cost and durability of the product. Some colors, such as bright red or bright yellow, if single azo pigments are used, the cost is not high but the weather resistance is poor, which cannot achieve the goal of long-term protection; If other pigments are used, the cost may increase significantly. Therefore, color design has become an essential part of bridge protective coating design. Designers should not only consider the requirements of the owners, but also take into account issues related to safety, cost, and weather resistance.

In short, color design should follow the principles of coordination and harmony among various aspects such as process aesthetics, coating performance, technical economy, and surrounding environment.

Design basis：ISO 12944/Railway industry/chemical industry/transportation industry

1. Basic standards

The painting design of bridges should fully consider the impact of atmospheric corrosion environment. ISO 12944-2:2017 "Paints and Varnishes - Protective Coating Systems for Corrosion Protection of Steel Structures - Part 2: Environmental Classification" and GB/T 15957-1995 Classification of Corrosivity in Atmospheric Environment It is currently the most widely used and practical standard in painting design. The specific classification method can refer to the relevant content of "Classification of Atmospheric Corrosion Environment" in the first section of this chapter.

2. Industry standards for anti-corrosion coating of bridges

(1) Railway industry standards

In the early days, China's railway industry formulated four industry standards for anti-corrosion protection of steel bridges. The standard TB/T 2486-1994 "Evaluation of Coating Degradation of Railway Steel Beams" specifies the types, grades, and evaluation methods of coating degradation of railway steel beams, and is applicable to evaluating the status and quality of steel beam coatings Classification of degraded coating coatings for railway steel beams and other steel structures for bridges; The standard TB/T 1527-2004 "Railway Steel Beam Protective Coating" specifies the technical requirements, test methods, and inspection rules for the protective coating of railway steel bridges. It is applicable to the initial coating of steel bridges and the re coating after the deterioration of the steel bridge coating Installation and maintenance coating; Standard TB/T2772-1997 "Technical Conditions for Supply of Anti rust Primer for Railway Steel Bridges" and TB/T 2773-1997 "Railway The "Technical Conditions for Supply of Topcoat and Intermediate Paint for Steel Bridges" respectively stipulate the classification, technical requirements, test methods, inspection rules, packaging, marking, transportation, and storage of rust proof primer, intermediate paint, and topcoat for various painting systems of railway steel bridges. It is applicable to the painting of newly built steel beams and the re painting of steel beams in operation Rust proof primer, intermediate coat, and topcoat used for installation and maintenance painting and other steel structure painting. In 2011, TB/T 2772-1997 and TB/T 2773-1997 were abolished and merged into TB/T 1527-2011 Technical Conditions for Protection Coating and Coating Supply of Railway Steel Bridges.

In 2020, the original standard TB/T 1527-2011 of the Ministry of Railways has also been abolished and replaced by the newly formulated enterprise standard Q/CR 749-2020 "Coating and Coating for Protection of Railway Bridge Steel Structures and Components" of China Railway Corporation. This standard is divided into Part 1 Steel bridge; Part 2 Support; Part 3: The three sub standards of pedestrian steel beams and ancillary steel structures sequentially specify railway steel beams; Support; The protective coating system, technical requirements, inspection methods, inspection rules, as well as coating packaging, labeling, transportation, and storage for sidewalk steel beams and ancillary steel structures, Suitable for initial coating, recoating after film degradation, and maintenance coating of these three types of structures, as well as rust proof primer, intermediate coat, and topcoat used for coating.

(2) Chemical industry standards

According to the standard HG/T 3656-1999 "Steel Structure Bridge Paint", steel bridge coating products are divided into two categories based on their service life: ordinary and long-lasting. Provide technical requirements, testing methods, inspection rules, packaging, labeling, transportation, and storage for the anti rust primer, intermediate paint, and topcoat of these two types of products Regulations have been established. At the same time, the appendix lists the commonly used varieties of two types of products and introduces several practical application supporting systems.

(3) Transportation industry standards

JT/T 722-2008 Technical Conditions for Coating of Steel Structures of Highway Bridges

JT/T 694-2007 Technical Conditions for Anti corrosion Coating of Main Cables of Suspension Bridges

JT/T 695-2007 Concrete Bridge Surface Coating Anti corrosion Technical Conditions

JT/T 722-2008 will be revised in 2020. The newly revised standard reflects the progressiveness and forward-looking nature of coatings and coatings in the field of transportation and bridges. While promoting advanced and mature technologies and successful experience, it provides methods and basis for the introduction of new products, new technologies and new processes According to. The revision of the standard focuses on the full life cycle economy and environmental protection of bridge durability. It not only attaches importance to drawing on the development achievements and lessons learned from domestic anti-corrosion coating practices in recent years, but also draws on advanced international experience, especially the new version of IS012944 and foreign bridges Specification for anti-corrosion coating; The JT/T 694-2007 standard is applicable to the anti-corrosion coating of the main cable system of suspension bridges. In addition to specifying relevant terms and definitions, it focuses on designing and specifying the matching system of coating materials for the main cable system, construction technology, performance indicators of related materials, as well as acceptance, safety, hygiene, and environmental protection Security, etc; JT/T 695-2007 standard, based on the analysis of corrosion environment and corrosion factors for concrete bridges, specifies the design of concrete

The surface coating system and its performance indicators of bridges under various corrosion environment conditions, and specific regulations are made for coating construction, acceptance, safety, hygiene, and environmental protection. JT/T 694-2007 and JT/T The two standards 695-2007 will also be revised in the coming years.

Anti corrosion scheme for concrete bridge renovation

1. Renovation of concrete bridges

Due to the strong alkaline nature of concrete as a building material, it is required that concrete anti-corrosion coatings have good alkali resistance, adhesion, and impermeability. In addition, the coating itself should also have good weather resistance and long-term durability. For concrete structures of seaside bridges, the surface coating should have excellent weather resistance, resistance to sunlight and ultraviolet degradation, resistance to salt spray and marine atmospheric corrosion, and should not exhibit serious powdering, discoloration, peeling, cracking, and other phenomena during the effective protection period.

According to relevant regulations and standards such as JTJ275-2001 "Technical Specification for Anti corrosion of Concrete Structures in Port Engineering", GB50046-95 "Code for Anti corrosion Design of Industrial Buildings", and GB50212-2002 "Code for Construction and Acceptance of Building Anti corrosion", epoxy resin coatings, polyurethane coatings, chlorinated rubber coatings, vinyl resin coatings, acrylic coatings, etc Acid resin coatings, etc. Considered as a suitable coating variety. Based on the experience of anti-corrosion coatings for bridge concrete at home and abroad, the following coatings can be used to achieve good coating effects.

A1: Mengneng Coatings recommends anti-corrosion paint solutions for bridge surfaces, pier caps, piers, baffles, guardrails, and pavement renovation in the Atmospheric zone

A2: Mengneng Coatings recommends renovating paint anti-corrosion schemes for underwater areas and wet dry alternating areas of bridge piers

New construction plan for concrete bridge

1. Corrosion threat faced by concrete bridges

Due to the strong alkaline nature of concrete as a building material, experts in Dreaming Coatings believe that concrete anti-corrosion coatings are required to have good alkali resistance, adhesion, and impermeability. In addition, the coating itself should also have good weather resistance and long-term durability. For concrete structures of seaside bridges, the surface coating should have excellent weather resistance, resistance to sunlight and ultraviolet degradation, resistance to salt spray and marine atmospheric corrosion, and should not exhibit serious powdering, discoloration, peeling, cracking, and other phenomena during the effective protection period.

Corrosion of steel bars

Chloride ion erosion: Chloride ions in environments such as seawater, saline soil, and de icing salts can penetrate into concrete, damaging the passive film on the surface of steel bars and causing them to rust

Carbonization: Carbon dioxide (CO2) in the atmosphere reacts with calcium hydroxide (Ca (OH) 2) in concrete to produce calcium carbonate (CaCO2), which lowers the pH value of the concrete and reduces its protective effect on steel reinforcement

Moisture and oxygen: Steel bars exposed to moisture and oxygen environments are prone to electrochemical corrosion

Concrete deterioration

Carbonization: Carbonization of concrete not only reduces the pH value of concrete and reduces the protection of steel bars, but also leads to a decrease in the structural performance of concrete

Freeze thaw cycle: In cold regions, the moisture in concrete freezes and expands, and repeated freeze-thaw cycles can cause microcracks on the interior surface of concrete, ultimately leading to concrete spalling

Sulfate erosion: When concrete comes into contact with groundwater or soil containing sulfates, sulfate ions react with calcium ions in the concrete to produce expansive products, causing the concrete to expand and eventually rupture

Physical damage

Physical impact: External surface physical factors such as vehicle impact and rockfall may cause concrete damage

Vibration: Long term traffic loads and vibrations may also cause fatigue damage to concrete

Chemical erosion

Acidic environment: In certain industrial areas or acid rain environments, concrete may be subject to erosion by acidic substances

Other chemical substances, such as certain solvents, oils, etc., may also cause damage to concrete

Microbial corrosion

Microbial induced corrosion: Microbial activity in specific environments may promote the corrosion process of concrete and steel bars

These corrosion threats can affect the safety and durability of concrete bridges, so appropriate protective measures need to be taken to extend the service life of the bridge, such as using high-quality concrete, implementing cathodic protection, regular inspections and maintenance, etc

2. Graphene coating anti-corrosion scheme is adopted for concrete bridges

Reference standards: JT/T 695-2007 Technical Conditions for Surface Coating Anti corrosion of Concrete Bridge Structures

The classification of concrete bridges is mainly based on their structure and components. Concrete bridges typically consist of the following basic components:

Bridge deck: A bridge deck is a platform on top of a bridge, used to support the movement of vehicles and pedestrians. Bridge decks are usually made of materials such as asphalt, concrete, or steel plates to ensure their strength and durability

Support: A support is the connection point between a bridge and its foundation, designed to bear the weight of the bridge and the loads applied to it, and transmit these forces to the foundation. Bearings are usually made of rubber or steel to provide good load-bearing capacity and shock absorption effect

Main beam: The main beam is the main structural element of a bridge, responsible for carrying the load on the bridge and transferring it to the supports. The main beam is usually made of concrete, steel, or prestressed concrete, which has high strength and durability

Pier column: A pier column is a vertical support structure of a bridge, used to support the main beam and the load on the bridge. Pier columns are usually made of concrete or steel and have good load-bearing capacity and structural stability

Foundation: The foundation of a bridge is a structure that supports the bridge on the ground. The foundation is usually made of concrete or steel, with sufficient strength and stability to support the loads on the bridge

In addition, the bridge also includes other components such as tie beams, abutments, columns, cover beams, bearing pads, etc. These components work together to ensure the structural safety and stability of the bridge

B1. Mengneng Coatings recommends anti-corrosion solutions for bridges, pier caps, bridge decks, piers, barriers, guardrails, and paving in the Atmospheric zone

B2. Mengneng Coatings recommends anti-corrosion solutions for underwater and wet dry alternating parts of bridge piers

New construction plan for steel structure bridge

1. Steel structure bridges are facing corrosion

Steel structure bridges stand outdoors all day long, exposed to sunlight and rain, and are easily corroded by the medium. Without effective anti-corrosion methods to protect the steel structure, the service life of the steel bridge will significantly decrease or even be scrapped prematurely

1. Uniform corrosion

Uniform corrosion is the most common form of corrosion, characterized by corrosion distributed throughout the entire metal surface and causing the overall thickness of the metal to decrease at the same rate. Although uniform corrosion causes significant metal loss, it is not scary. Due to the uniform corrosion rate, it can be easily predicted and protected, As long as strict engineering design is carried out and reasonable anti-corrosion measures are taken, steel bridges generally do not experience sudden corrosion accidents

2. Pitting corrosion

In a suitable environmental medium, most of the surface of steel is not corroded after a certain period of time, but in individual points or micro areas, corrosion holes or pitting appear due to selective corrosion of the metal. With the increase of time, the corrosion holes develop in the depth direction, and this corrosion form is called pitting corrosion. The occurrence of pitting corrosion is generally due to Cl -It is caused by some defects in the facial mask of the metal surface. For example, a cable stayed bridge in Guangdong was built in December 1988, and the upper section of one cable suddenly broke in 1995. Through analysis, its corrosion product was found to contain 0 1% Cl - and 0 1 %SO42 - , The main cause of its fracture is due to Cl - pitting corrosion

3. Gap corrosion

Gap corrosion is a localized form of corrosion that occurs when there are gaps on the surface of metal to metal or metal to non-metal connections in the presence of corrosive media. It mainly occurs in metal riveting, bolt connections, screw joints, flange washers of non-metallic materials, and between metal materials

2. Anti corrosion coating for bridge steel structures

The commonly used anti-corrosion measures for steel structures are mainly divided into two categories: one is mechanical isolation measures, which use inert materials to cover the surface of the steel structure and isolate corrosive media such as water and oxygen to achieve the purpose of anti-corrosion; Another type is to artificially increase the potential of steel structures based on the principle of electrochemical corrosion, Place it at the higher potential pole to achieve the purpose of protection. Based on the above principles, commonly used anti-corrosion methods for steel structures include flame spraying, hot-dip coating, paint coating, arc spraying composite coating, etc

The use of coatings for anti-corrosion protection of steel bridges has been over 100 years, and through continuous development and extensive application, a series of specialized bridge coatings have now been formed. Due to the fact that no coating can guarantee simultaneous isolation, UV resistance, and cathodic protection for steel, Therefore, the coating of steel bridge beams is usually a comprehensive anti-corrosion system composed of primer, intermediate paint, and topcoat with good corrosion resistance, weather resistance, and construction performance. The main corrosion principle is the combined effect of mechanical shielding, passivation and corrosion inhibition, and cathodic protection

A1. Inner surface of air nozzle and structural support

Wind Mouth (Wind) Faring is a special structure of the steel box girder section of a bridge, consisting of upstream and downstream top, bottom, and web plates forming a specific shape to improve the aerodynamic performance of the section and enhance the wind resistance stability of the bridge section. Bridge wind nozzles are design measures taken to reduce the resonance caused by strong winds on the bridge deck structure

*The above solution adopts the fourth generation graphene coating solution. If you need other solutions, please contact us

A2. External surface of ancillary facilities

Bridge ancillary facilities include bridge deck systems, expansion joints, bridge approach slabs, cone slopes, drainage facilities, etc.

*The above solution adopts the fourth generation graphene coating solution. If you need other solutions, please contact us

A3. Steel box girder, steel anchor box, and structural support bolt connection parts

Steel Box Girder: A steel box girder is a type of bridge structure with a cross-sectional shape similar to a box, welded from steel plates. It is mainly used in the construction of large-span bridges due to its good structural rigidity, strong bearing capacity, light weight, and superior seismic performance

Steel Anchor Box: A steel anchor box is a structure used to secure the main or diagonal cables in suspension or cable-stayed bridges. It is mainly used to bear the tension transmitted by the main cable or inclined cable, and evenly distribute these forces to the bridge tower or pier

Node connector: Node connector refers to a connector used at steel structure nodes to connect components in multiple directions, such as members in truss structures. It is a high-strength connection method that can withstand large axial and shear forces

*The above solution adopts the third-generation Cold spray zinc coating solution. If you need other solutions, please contact us

A4. Outer surface of box girder and structural support

Box girder: It is a closed section beam structure commonly used in the design of large-span bridges, such as continuous beam bridges or cantilever beam bridges. A box girder consists of a top plate, a bottom plate, and web plates on both sides, forming a closed box structure

Structural brace: refers to a connecting element used at steel structure nodes to connect components in multiple directions, such as members in truss structures. It is a high-strength connection method that can withstand large axial and shear forces

*The above solution adopts the third-generation Cold spray zinc coating solution. If you need other solutions, please contact us

A5. Inner surface of box girder

The anti-corrosion treatment of the inner surface of the box girder is also very important, because the interior surface of the box girder is prone to moisture accumulation and difficult to ventilate, making it a particularly susceptible environment to corrosion

*The above solution adopts the third-generation Cold spray zinc coating solution. If you need other solutions, please contact us

Fire prevention of suspension bridges

1. The impact of bridge main cable on fire

With the increasing number of vehicles and traffic, cable system bridge fire accidents caused by traffic accidents occur from time to time. As an important load-bearing component of cable supported bridge systems, cables have relatively good mechanical properties and weather resistance. However, the fire resistance of their constituent materials, such as high-strength steel wire, polyester fiber tape, PE sheath, and anti-corrosion coating, is poor. When a fire accident occurs on the bridge deck (especially in an oil tanker fire accident), the PE sheath is easily burned, the steel wire temperature continues to rise, the anti-corrosion layer falls off, and the steel wire performance deteriorates, posing a serious threat to the safe operation of the bridge. See Table 1 and Figure 1. At present, there is no relevant specification for fire protection design of load-bearing steel structures in the industry, so there is a lack of corresponding guidance standards on how to protect important steel components such as cables in fire scenarios.

Suspension bridges have become an important component of modern bridge engineering due to their unique structural design. However, this structure will face serious safety challenges in the event of a fire. As the core component of a suspension bridge, the fire resistance performance of the main cable is crucial for ensuring the overall safety of the bridge. This article aims to explore and propose a comprehensive coating fire prevention scheme to enhance the protection capability of the main cables of suspension bridges in case of fire.

1. Challenge of Main Cable Fire in Suspension Bridges

The challenges faced by suspension bridges in fires mainly include the following aspects:

Main cable damaged by heat: High temperature may cause a decrease in the strength of the main cable, or even fracture.

Structural stability: The high temperature generated by a fire can affect the overall structural stability of the bridge.

Rescue difficulty: The height and span of suspension bridges make firefighting and rescue more complex.

Table 1 List of Fire Damage Accidents in Cable System Bridges

Serial number	Accident time	Bridge name	Cause of fire
one	April 2009	A cable-stayed bridge in Wuhu	Bus caught fire
two	October 2011	A cable-stayed bridge in Nanjing	Truck spontaneous combustion
three	November 2011	A bridge in Harbin	Multiple vehicles caught fire and burned
four	October 2014	Guangdong Panyu Bridge	Truck spontaneous combustion
five	January 2014	A bridge on the Zhengshao Expressway	Gasoline tanker truck catches fire
six	June 2017	A bridge on the Guangkun Expressway	Truck spontaneous combustion
seven	March 2018	A cable-stayed bridge in Hubei Province	Truck spontaneous combustion
eight	July 2020	A cable-stayed bridge in Wuhan	Truck spontaneous combustion
nine	July 2021	A suspension bridge in Nanjing	A white oil tanker truck caught fire
ten	September 2022	An elevated bridge in Anhui province	Silicon oil tanker truck catches fire

2. Problems with traditional fire-resistant materials

The fire-resistant materials for bridge cables need to balance the two major functional requirements of fire resistance and thermal insulation. At the same time, in order to meet the needs of cable wrapping construction, the materials also need to have a certain degree of flexibility. In addition, as a semi permanent protective measure for bridges, the bridge cable fire protection system also needs to consider the requirements of environmental aging resistance, such as UV aging resistance, waterproofing, acid rain corrosion resistance, and adaptability to bridge structural vibration.

After a lot of research and comparison, the materials with potential application of cable fire and heat insulation are mainly felt fire retardant materials, such as basalt fiber needled felt, ceramic fiber needled felt or aerogel thermal insulation felt. Further differentiation is needed for felt products based on different performance parameters such as mechanical strength, temperature resistance level, and thermal conductivity. The advantages and disadvantages of the main fire-resistant materials are shown in Table 2.

Material category	texture of material	performance	cable Applicability
Cotton category	asbestos	Carcinogens, explicitly prohibited	Not applicable
	Ultra fine glass wool	Poor heat resistance, average insulation effect	Not applicable
	Rock wool	Cheap, low-end, low strength, poor insulation	Not applicable
Board type	Calcium silicate board	High rigidity, poor flexibility	Not applicable
	Basalt slab	High rigidity, poor flexibility	Not applicable
	Aluminum silicate	High rigidity, poor flexibility	Not applicable
Paint category	Fireproof coating	PE has poor adhesion, low strength, and is prone to cracking	Not applicable
Felt type	Basalt fiber felt	In terms of thermal conductivity, it has high strength and average heat resistance	Potential applications
	Ceramic fiber needle punched felt	In terms of thermal conductivity, Moderate strength, excellent heat resistance	Potential applications
	Ordinary aerogel Thermal insulation felt	Low thermal conductivity,average strength, average heat resistance	Potential applications

A1. Main cable fireproof coating

Mengneng aerogel fireproof coating is a new type of coating made of aerogel materials, which has the following characteristics:

1. Low thermal conductivity: The pore size of aerogels is usually between 2nm and 50nm, and this nano scale pore structure can greatly reduce the heat conduction. The extremely low thermal conductivity means that it can effectively isolate heat and reduce the transfer of thermal energy from high temperature areas to low temperature areas. Under normal temperature and pressure, it can reach 0.013w/m · k

2. Efficient insulation: The pore structure of aerogel can prevent the flow of air molecules between pores, thus reducing the thermal convection. This structure can also reduce thermal radiation and further improve insulation performance.

3. High temperature resistance: Aerogel itself is a kind of high temperature resistant material, which can maintain structural stability even under high temperature conditions. Therefore, the aerogel fireproof coating can maintain its thermal insulation performance for a long time under high temperature environment.

4. Improve material strength and adhesion: By adjusting the formula, the mechanical strength of the coating and its adhesion to the substrate can be further improved, ensuring the integrity and long-term performance of the coating.

5. Waterproof and corrosion-resistant: The aerogel fireproof coating has good waterproof performance and can prevent moisture penetration. The water increase rate is greater than 99%. At the same time, it also has corrosion resistance, which can protect the substrate from chemical erosion.

6. Fire resistance performance: Aerogel itself is a non combustible material, which can improve the overall fire resistance of the coating. When the coating is formed, it can effectively isolate the contact between the flame and the substrate, preventing the flame from spreading. Fire rating A1, smoke rating AQ1

7. Environmental Protection: Air gel fire retardant coating usually contains no volatile organic compounds (VOCs) and is friendly to human body and environment.

8. Easy construction: Air gel fireproof coating can be applied by conventional spraying, brushing and other methods, which is convenient and fast. However, it should be noted that during the construction process, it is necessary to ensure the compactness of the coating to achieve the best insulation effect.

9. Strong adaptability: It can be applied to various substrates such as metal, concrete, etc., and is suitable for various occasions such as buildings and equipment.

10. Extend Service Life: Due to its excellent thermal insulation and fire resistance, it can effectively protect the substrate and extend the service life of the structure.

In conclusion, aerogel fire retardant coating has been widely used in industrial and civil buildings due to its excellent heat insulation and fire resistance. During the construction process, it is necessary to pay attention to the correct application and maintenance of coatings to ensure their long-term effectiveness.

Design basis	ISO12944-5：2017 Corrosion Protection of Steel Structures by Paint and Varnish Protective Paint Systems
Current environment	C5 High；outer surface：Industrial areas with high humidity and severe weather, and coastal areas with high salinity
Design Life	VH ultra long term
Surface Treatment	ISO 8501-1 St2：Thoroughly removing rust by hand and power tools, the steel surface should be free of visible grease and dirt, and there should be no loosely attached oxide scales, rust, paint layers, or other attachments.
Thoroughly spray rust removal to Sa2.5 level (ISO) 8501-1:2007), when observed without magnification, the surface should be free of visible oil, grease, and dirt, and there should be no oxide scale, rust, coating, or foreign impurities. Any residual traces of pollutants should only appear as slight color spots in the form of dots or stripes. Painting area	Main cable, sling and diagonal cable

Cable anti icing solution

1. The hazards of bridge cable icing

The lower part of the suspension cables of cable-stayed bridges and suspension bridges is the bridge deck. In winter, when the temperature is low, the wind speed is high, and the humidity is high, the bridge cables are prone to icing. Freezing of the bridge cables can bring a series of safety hazards and potential hazards, including the following aspects:

1. Increase cable load: The weight of ice will bring additional load to the cable, especially in the case of thick ice accumulation, which may cause an imbalance in cable tension and affect the stability and safety of the entire bridge structure.

2. Reduce cable strength: Freezing may cause changes in the physical properties of cable materials, such as some materials becoming brittle under extreme cold conditions, thereby reducing the tensile strength of the cable.

3. Ice formation: Water droplets formed at the bottom of the ice melting cable during the day will freeze again at the bottom to form ice when the temperature drops at night. When the ice grows to a certain extent or the temperature of the cable rises, the root of the ice breaks and falls, posing a danger to pedestrians and vehicles on the bridge deck.

4. Increase friction: Freezing will increase the friction between cables, affecting the normal movement of cables and the dynamic characteristics of bridges, especially when cables need to be moved or tension adjusted.

5. Structural stability is affected: Cable icing can lead to a decrease in the overall structural stability of the bridge, especially in adverse weather conditions such as strong winds, which may cause increased vibration or oscillation of the bridge.

6. Increase maintenance costs: Freezing can cause damage to the cable surface, increasing maintenance frequency and costs. In addition, the presence of ice also increases the difficulty of maintenance work.

7. Safety hazards: The falling of ice not only poses a direct threat to pedestrians and vehicles on the bridge deck, but may also cause harm to ships and other vehicles below the bridge.

8. Impact on aesthetics: Freezing can damage the overall appearance of the bridge, especially when ice columns form on the cables. Although it may appear spectacular, it is also a safety hazard.

9. Impact on traffic: If the icing is severe enough to affect the safety of the bridge, it may cause traffic interruption or restrictions, affecting people's travel. To avoid these hazards, Mengneng Coatings has developed some anti icing and de icing technologies, using carbon nanotube materials applied to cables and coated with superhydrophobic coatings, or using heating cables, vibration devices, and other methods to prevent icing. In addition, measures such as hydrophobic coating and chemical anti icing agents can be used to reduce the formation of ice layers. These dream coating technologies and measures help improve the reliability and safety of bridge cables in winter.

2. Using Dreamenergy carbon nanotube coating to solve cable anti icing

Coating carbon nanotube materials on bridge cables, combined with superhydrophobic coating, can prevent cable icing by heating at low temperatures. Mengneng carbon nanotube coating technology has very high conductivity and a certain resistance. When current passes through carbon nanotubes, heat is generated due to the resistance effect. This heating method is very efficient and controllable, which can quickly increase the temperature of the cable, thereby melting the ice layer or preventing the formation of ice layer.

2.1 Advantages of carbon nanotube coating technology

Knka Technology mixes carbon nanotubes with coatings to prepare composite materials. This composite material can be directly wrapped around the cable or embedded in the interior surface of the cable to form a heating system.

1. Efficient and energy-saving: Carbon nanotubes have fast heating speed and high energy conversion efficiency.

2. Uniform heating: Carbon nanotubes can provide uniform heating distribution, avoiding local overheating.

3. Lightweight: Carbon nanotube heating elements are lightweight and do not increase the burden on cables.

4. Flexibility: The shape and size of the heating element can be customized according to the specific needs of the cable.

2.2 Knka Anti icing Coating Solution

Knka anti icing paint two-component packaging, the paint material is composed of fluorocarbon resin, pigments, solvents, additives, etc; The other component is aliphatic isocyanate curing agent, which aims to prevent the surface of objects from freezing or reduce the formation of ice layers. This type of coating usually has the following characteristics:

1. Low surface energy: Knka anti icing paint has low surface energy and can make it difficult for water or ice to adhere to the coating.

2. Superhydrophobicity: Knka anti icing paint has superhydrophobic properties, which can significantly reduce the contact area between water droplets and the surface.

3. Large contact angle: Anti icing coating can reduce the adhesion of ice, making it easier for ice to slide off the surface.

4. Low friction coefficient: The surface of Knka anti icing paint usually has a low friction coefficient, making it difficult for the ice layer to firmly adhere to the surface.

5. Self cleaning function: As anti icing paint can reduce the formation of ice layers, it also reduces the workload of cleaning ice layers.

6. Weather resistance: Anti icing paints usually have good weather resistance and can maintain their performance for a long time in outdoor environments.

7. Easy to apply: Knka anti icing paint can usually be applied using common painting methods such as spraying, brushing, etc.

Knka anti icing paint is widely used on aircraft surfaces to prevent icing from affecting flight safety; Wire and cable, to prevent line faults caused by icing; Reduce safety hazards caused by icing on bridges, road signs, etc; Wind turbine blades prevent icing from affecting power generation efficiency.

Other special substrates

1.Hot dip zinc substrate

Hot dip galvanizing is a commonly used method for metal surface anti-corrosion treatment, which provides protection by forming a layer of zinc iron alloy on the surface of steel products

2.Stainless steel substrate

Stainless steel itself has excellent corrosion resistance, but in some cases, additional anti-corrosion measures are still needed to increase its durability and aesthetics.

Bridge Maintenance: Failure Analysis/Basis/Coating Selection/Construction

1、 Failure analysis of anti-corrosion coating

The failure of anti-corrosion coating refers to the long-term exposure of the coating to a corrosion environment, which causes the deterioration of various physical and chemical properties, resulting in the loss of its original performance and partial or complete loss of its protective effect on the bridge substrate.

The failure of anti-corrosion coating on bridges is mainly divided into two categories: organic coating failure and metal coating failure.

1. Failure analysis of organic coating

The main reasons for the damage to the coating are the erosion of chemical substances, or the long-term effects of external environments such as ultraviolet radiation, hot and cold rainwater, as well as the swelling and diffusion of corrosive media on the coating.

2. Failure analysis of metal coating

For metal coatings such as hot spray zinc, hot spray aluminum, hot-dip zinc, as well as zinc rich coatings with metal coating characteristics, they all utilize the cathodic protection effect of zinc or aluminum during use, sacrificing themselves to protect steel substrates. The failure mode of metal coating is uniform chemical or electrochemical corrosion, and its corrosion life can be calculated based on the corrosion rate of the coating obtained from experiments, given the known thickness of the metal coating. The corrosion failure of rich zinc coating combines the characteristics of organic coating and metal coating. On the one hand, rich zinc coating has a cathodic protection effect on steel; On the other hand, the failure of organic coating can lead to weak adhesion or detachment of metal zinc powder, rendering it ineffective. Therefore, for rich zinc coating, the service life of the coating depends on which of the above two factors is more dominant.

3. Failure of composite coating

The heavy anti-corrosion system of modern bridges is a protective coating that combines metal coating and organic coating. The organic coating on the outer layer can effectively block the corrosion factors from corroding the metal coating and steel. The first failure of composite coating is the failure of the outer organic coating, which is mostly caused by powdering, peeling, etc. Due to the damage of organic coating, corrosion factors have the opportunity to penetrate the bottom surface, causing corrosion failure of metal coating. The generation and accumulation of corrosion products can also lead to a decrease in the adhesion of organic coating.

2、 Basis for repairing and painting

Due to the corrosion failure of anti-corrosion coating, it is necessary to update and maintain the original anti-corrosion coating for a certain period of time in order to protect the safety and durability of the bridge. But what is the basis for updating and maintaining? Simply put, how to determine the degree of failure of the original coating on a bridge - whether it is partial or complete? When is it necessary to update and maintain bridges while ensuring greater economy and rationality?

GB/T 1766-1995 "Rating Methods for Aging of Coatings and Varnishes" (Referring to ISO) 4628/1-5-1982) provided a detailed evaluation method, grading the degree of corrosion failure of organic coatings based on factors such as foaming, rusting, cracking, and peeling, providing a simple and clear basis for relevant management and maintenance departments to develop maintenance plans.

According to the above criteria, it is generally considered that when the comprehensive level of organic coating failure reaches 3 (S3) or 4 (S4), the coating should be updated and repaired as soon as possible.

It is necessary to explain the corrosion listed in the above standards. The occurrence of rust is caused by improper surface treatment of the substrate, low coating thickness, or improper coating application, resulting in the presence of through holes. The appearance of rust indicates that the coating has completely lost its effectiveness in certain areas, which also affects the overall anti-corrosion performance of the organic coating. At the same time, the accumulation of corrosion products at the rust spots will also accelerate the failure of the surrounding coating, such as foaming, peeling, and aging. According to anti-corrosion technology, the corrosion area grade of the coating has reached level 3 (equivalent to ISO) Ri 3 in 4628/3 or Re according to European standards 3) The coating should be repaired and painted. So for bridge structures, when the topcoat has a powdering level of 3 or above, and the thickness of the powdering thinning is greater than 50% of the initial thickness, or due to landscape requirements, after thoroughly cleaning the topcoat, apply 1-2 coats of matching topcoat compatible with the original coating; When the coating is cracked at level (2-3), peeled off at level (2-3), or blistered at level (2-3), but the base coating is intact, choose the corresponding intermediate paint or topcoat for repair coating; When Ri2~Ri3 corrosion occurs on the coating, thoroughly clean the surface and apply the corresponding primer, intermediate coat, and topcoat.

3、 Maintenance coating design and construction

Developing a maintenance and painting plan for a bridge is much more complex than developing a painting procedure for a newly constructed bridge. There must be a systematic approach and specific testing to determine the status of the original coating and the integrity of the overall structure; At the same time, it is necessary to carefully study and consider the conditions of the construction site, as well as relevant environmental and safety laws and regulations, in order to develop a targeted maintenance plan.

4、 Selection of Coatings for Maintenance Coating

Before selecting a repair coating, a comprehensive analysis of the original coating should be conducted first. These tasks include analyzing the adhesion status of the original coating and the matching system of the original coating. By conducting some simple on-site tests, one can roughly understand the condition of the original coating. For example, the grid method test (GB/T 9286-1988) can easily and quickly understand the adhesion status of coatings (between coatings, between coating interior surfaces, or between coatings and substrates); The solvent MEK (methyl ethyl ketone) wiping method can roughly analyze the type of coating applied based on its condition after wiping (dissolution, biting or wrinkling, minimal impact), including physical drying, oxidation curing, or chemical curing. Of course, the results of these tests are rough and can only be used as a reference basis. To obtain accurate results, additional methods or laboratory tests are needed.

Secondly, it is necessary to consider the requirements of the selected coating for the Surface Treatment, the working conditions at the maintenance site, and the corresponding painting equipment and techniques.

Only by conducting the above tests and analysis, taking into account the compatibility factors between coatings, and designing the service life of coatings, can suitable maintenance coatings be selected.

5、 Construction of maintenance coating

According to the degree of aging of the original coating, repair coating can choose between partial repair or overall refurbishment. Partial repairs can be carried out using simple manual power tools to perform Surface Treatment on the parts that need to be repaired, using methods such as roller coating, brush coating, or spray coating. The overall renovation requires the original coating to be completely removed and a suitable Surface Treatment method (usually sandblasting for rust removal) to be used. According to the painting construction requirements of the new bridge structure, a new anti-corrosion coating should be applied.