I. WATER CONSERVANCY MECHANICAL CORROSION BACKGROUND

Water conservancy machinery's common metal structures work in harsh environments, including exposure to sunlight, damp and dark conditions, alternating dry and wet periods, frequent immersion in water, high-speed water flow erosion, biological corrosion, sediment, ice, and other floating debris. These factors make the structures highly prone to rusting. Therefore, ensuring corrosion protection for water conservancy machinery's metal structures is critically important for safety, prolonging service life, and conserving metal materials.

Metal corrosion occurs in two forms: chemical corrosion and electrochemical corrosion. Chemical corrosion happens without the presence of electrical current, while electrochemical corrosion occurs when metal comes into contact with an electrolyte solution, creating countless small corrosion cells that result in corrosion. The corrosion of water conservancy machinery's metal structures primarily falls under electrochemical corrosion, which can severely damage the structure, posing significant risks. This corrosion process is similar to the discharging mechanism of dry cells used in daily life, where one of the metals inside the battery corrodes to release energy.

I. Reference Standards

Current national standards, relevant regulations, and mandatory standard provisions;

"Code for Construction and Acceptance of Building Anti-corrosion Engineering" (GB50212-2002)

"Standard for Corrosion and Rust Removal Levels of Steel Surface Before Coating" (GB8923-1988)

"Safety Regulations for Coating Operations and Safety Management Rules" (GB6514-1995)

"Quality Requirements for Anti-corrosion Coatings" (GB6514-1991)

"Safety Regulations for Coating Operations, Paint Process Safety, and Ventilation Purification" (DJ/T6931-1999)

"Code for Construction and Acceptance of Industrial Equipment and Pipeline Anti-corrosion Engineering" (HGJ229-91)

"Safety Regulations for Coating Operations and Safety of Surface Preparation Process" (GB7692-87)

"Noise Limits at Construction Sites" (GB12523-90)

ISO9001 Quality Management System Documents

ISO14001 Environmental Management System Documents

GB/T28001 Occupational Health and Safety Management System Documents

I. Design Basis

Environmental Conditions: The corrosion level of atmospheric environments on steel structures can be determined according to Table 1.

I. Gate Anti-Corrosion Plan

Corrosion not only affects the safe operation of the structure but also consumes a large amount of manpower, materials, and financial resources for anti-corrosion work. According to statistics from some sluice gate projects, the annual budget for gate anti-corrosion accounts for about half of the total annual maintenance costs. Moreover, a large workforce is required for tasks such as rust removal, painting, or spraying. Therefore, in order to effectively control the corrosion of steel and extend the service life of steel sluice gates, ensuring the integrity and safety of water conservancy and hydropower projects, the long-term anti-corrosion of steel sluice gates has attracted widespread attention.

In water conservancy and hydropower projects, steel sluice gates and steel structures are sometimes submerged in various water qualities (seawater, freshwater, industrial wastewater, etc.); sometimes due to water level changes or frequent opening and closing, they are exposed to a dry-wet alternating environment; some may also be subjected to the impact of high-speed water flow, abrasion by sand, floating objects, and ice; parts of the structure above the water surface may be affected by the humid atmosphere and splashing water mist; structures working in the atmosphere are exposed to sunlight and air. Given the harsh working environment and multiple influencing factors, it is necessary to analyze the corrosion factors.

The factors contributing to the corrosion of sluice gates are:

1) Climate factors: The upper part of the sluice gate above the water is easily affected by sunlight, rain, and humid atmosphere, leading to corrosion.

2) Surface condition of steel structures: Rough surfaces, mechanical damage, holes, welding defects, and gaps have a significant impact on corrosion.

3) Stress and deformation: The greater the stress and deformation, the more severe the corrosion.

4) Water quality: Freshwater has a low salt content, and the corrosion of the gate depends on its chemical composition and pollution. Seawater has a high salt content, good conductivity, and contains large amounts of chloride ions, which greatly increase the corrosion of steel. Gates in seawater experience more serious corrosion.

5) Water flow speed: The gate is subjected to high-speed impact from water flow and sand particles, causing erosive wear on the metal surface. Meanwhile, the flow of water enhances polarization, which easily washes away corrosion products from the structure surface, accelerating the corrosion process. Therefore, gates that are frequently opened to discharge water corrode more than those that remain closed for long periods.

Table 1: Anti-Corrosion Plan for Steel Sluice Gates Using Hot-Dip Galvanizing + Paint

The hot-dip galvanizing process is an anti-corrosion construction technology for sluice gates. It involves spraying zinc that is melted at high temperatures into particles and spraying it onto the surface of the sluice gate to form a zinc-iron alloy layer, achieving corrosion resistance and rust prevention. Specifically, the hot-dip galvanizing process includes surface preparation (such as sandblasting for rust removal), hot-dip coating (using a flame wire spray gun to apply zinc, with a coating thickness of approximately 160 μm), and post-treatment (combining brush coating and spray painting, with specific requirements for the thickness of primer and topcoat). This process not only improves the corrosion resistance of the gate but also extends its service life.

Table 2: Anti-Corrosion Plan for Steel Sluice Gates Using Cold Spray Zinc

The advantages of using cold spray zinc instead of hot-dip galvanizing are mainly reflected in the following aspects: First, cold spray zinc is simpler and more efficient in application, as it can be applied using brushing, rolling, or spraying methods, making it more flexible and easier to operate compared to the complex hot-dip galvanizing process. Second, cold spray zinc is more environmentally friendly, as it generates fewer pollutants and has a lower impact on the environment and human health, in line with national environmental policies. Furthermore, cold spray zinc consumes less energy, as it does not require maintaining a high-temperature environment like hot-dip galvanizing. Additionally, cold spray zinc coatings have better durability, longer maintenance cycles, and reduced long-term maintenance costs. Lastly, when cold spray zinc coatings suffer local damage, they are easier to repair by directly coating the damaged area, whereas hot-dip galvanized coatings often require a complex pre-treatment process for repair.

Table 3: Graphene Coating Anti-corrosion Solution for Steel Sluice Gates

The application of graphene coatings to sluice gates offers significant advantages: its high specific surface area and conductivity improve anti-corrosion performance, enhance substrate adhesion, reduce coating thickness while increasing wear resistance. The mechanical properties of graphene improve the coating's impact resistance and flexibility, adapting to environmental changes and reducing cracking. It is environmentally friendly and non-toxic, improving sluice gate efficiency, reducing maintenance costs, and making it an ideal choice that combines both environmental and performance benefits.

I. New Corrosion Protection Scheme for the Hoist

Hoists have been widely used in hydraulic machinery. They are highly efficient, reliable in performance, and safe in operation. However, hoists primarily control the important components for water level regulation in hydraulic machinery. Being submerged underwater for long periods, the hoists are subjected to frequent dry and wet cycles during operation, as well as erosion from high-speed water currents. In particular, the waterline area is affected by water, sunlight, and aquatic organisms. Additionally, it is exposed to erosion from waves, silt, ice, and other floating objects. Steel materials are highly susceptible to corrosion. If corrosion issues are not properly or promptly addressed, the failure rate will increase significantly, and the reliability and safety will be reduced, potentially even leading to accidents in the operation of hydraulic machinery.

Table 1: Graphene Paint Corrosion Protection Scheme for the Hoist

1. New Corrosion Protection Plan for Trash Screens

Trash screens are generally installed in water intake tunnels or at the inlet of pressure and suction pipelines to block debris such as branches and weeds carried by the water, ensuring the safe operation of hydraulic machinery. The trash screen consists of a frame, cross plates, and bars, supported by concrete piers, and is typically made of steel. Since trash screens are exposed to humid environments for extended periods, they are prone to corrosion due to the effects of water, air, and sediments.

The main factors contributing to the corrosion of trash screens:

1) Climatic factors: The upper parts of the gate are easily affected by sunlight, rain, and humid conditions, leading to corrosion;

2) Condition of the metal structure surface: Roughness, mechanical damage, voids, welding defects, gaps, etc., have a significant impact on corrosion;

3) Stress and deformation: The greater the stress and deformation, the more severe the corrosion.

4) Water quality: Freshwater has a low salt content, and the corrosion of gates depends on its chemical composition and pollution level; seawater has a high salt content, good electrical conductivity, and contains large amounts of chloride ions, which significantly accelerate the corrosion of steel. Therefore, gates in seawater suffer from severe corrosion.

Table 1: Paint Corrosion Protection Plan for Trash Screens (Renovation/New Construction)

1. New Corrosion Protection Plan for Winches

A winch is a small lifting device that uses a drum to wind a steel wire rope or chain for lifting or towing heavy objects, also known as a capstan. Winches can lift loads vertically, tow them horizontally, or pull them at an incline. They are mainly used for material lifting or dragging in construction, hydraulic engineering, forestry, mining, ports, and other industries.

Table 1: Corrosion Protection Plan for Winches Using Graphene Coating