Corrosion Resistance Technology of Fishplates and Adaptation Solutions for Different Track Lines
What are the anti-salt spray corrosion technologies for fishplates on coastal highways?
Corrosion of fishplates on coastal highways is mainly caused by salt spray erosion. The core of salt spray corrosion prevention is to construct a multi-layer protective system, preferentially employing a composite process of hot-dip galvanizing + sealing coating. The thickness of the hot-dip galvanized layer is controlled at 120-150μm, effectively isolating the steel from salt spray. After galvanizing, passivation treatment is performed, with a passivation film thickness of 1-2μm, which improves the corrosion resistance of the zinc layer and prevents white rust formation. The sealing coating uses fluorocarbon paint, with a coating thickness of 30-40μm. This coating has a salt spray resistance of ≥2000 hours, further blocking salt spray erosion. During production, the surface of the fishplate needs to be shot-blasted, with the surface roughness Ra controlled at 50-80μm to enhance the adhesion of the zinc layer and the coating. In addition, rubber sealing rings made of fluororubber are installed at the bolt holes of the fishplate to prevent salt spray from seeping in, forming all-around protection and ensuring that the fishplate can be used in coastal environments for more than 8 years without significant corrosion.
What is the chemical corrosion prevention solution for fishplates in saline-alkali areas?
Corrosion of fishplates in saline-alkali areas is mainly caused by acid and alkaline media. The core of chemical corrosion prevention is to improve the corrosion resistance and surface protection capabilities of the material. Weathering steel is selected, which contains corrosion-resistant elements such as copper and chromium. The corrosion rate in saline-alkali environments is ≤0.05mm/year. Surface protection uses a two-layer coating system of epoxy zinc-rich primer + polyurethane topcoat. The primer thickness is 50-60μm, and the zinc powder content is ≥80%, which can play a sacrificial anodic protection role; the topcoat thickness is 40-50μm, with excellent acid and alkali resistance. During construction, special treatment is required for the welded parts of the fishplate. After welding, the weld seam is ground smooth before the coating is applied to avoid the weld seam becoming a weak point for corrosion. Simultaneously, the surface flatness of the fishplate is controlled, with a flatness deviation ≤0.5mm/m, to prevent coating cracking due to stress concentration. Furthermore, the coating of the fishplate is inspected every six months, and any damage is repaired promptly to ensure continuous and stable protective effects.
What are the anti-corrosion strengthening measures for fishplates on heavy-load lines?
Heavy-load line fishplates not only face corrosion problems but also bear huge joint loads. Anti-corrosion strengthening must balance corrosion resistance and mechanical properties. The material selected is 40CrNiMoA high-strength corrosion-resistant steel, with a tensile strength ≥1080MPa after tempering, exhibiting superior corrosion resistance compared to ordinary carbon steel. The surface undergoes zinc diffusion treatment, with a zinc diffusion layer thickness of 50-80μm. The zinc diffusion layer forms a metallurgical bond with the steel, with a bonding strength ≥300MPa, making it difficult to peel off and providing excellent corrosion resistance. At the same time, stress concentration areas of the fishplate are rounded with a radius of 8mm to reduce stress concentration and prevent stress corrosion cracking. During production, the sulfur and phosphorus content of the steel must be strictly controlled, with sulfur content ≤0.025% and phosphorus content ≤0.025% to reduce the material's corrosion sensitivity. Furthermore, anti-corrosion gaskets made of polytetrafluoroethylene (PTFE) are installed at the contact points between the fishplate and the rail to isolate electrochemical corrosion and further enhance corrosion resistance.
What are the testing indicators and methods for the corrosion resistance of fishplates?
The main testing indicators for the corrosion resistance of fishplates include salt spray resistance, acid and alkali resistance, electrochemical corrosion rate, and coating adhesion. Salt spray resistance is tested using a neutral salt spray chamber at a salt spray concentration of 5% and a temperature of 35℃. After 1000 hours of continuous spraying, a corrosion area of ≤5% on the fishplate surface is considered合格 (qualified). Acid and alkali resistance is tested by immersing fishplate samples in 5% hydrochloric acid and 5% sodium hydroxide solutions, respectively. After immersion for 100 hours, a weight loss rate of ≤1% is considered qualified. Electrochemical corrosion rate testing was conducted using an electrochemical workstation, measuring the corrosion current density. A corrosion current density ≤10μA/cm² was considered合格 (qualified). Coating adhesion testing employed the cross-cut test method, with a 1mm spacing between the cuts. After cutting, the coating was peeled off with tape; a coating peel area ≤5% was considered qualified. Five samples were randomly selected from each batch for testing, and the average result was taken to ensure data accuracy.
What is the integrated corrosion and antifreeze technology for fishplates in high-altitude and cold regions?
Corrosion of fishplates in high-altitude and cold regions is mainly caused by de-icing agents and freeze-thaw cycles. Integrated corrosion and antifreeze technology requires addressing both material and protective aspects. Q355D low-temperature corrosion-resistant steel was selected, which has an impact energy ≥34J at -40℃, possessing both low-temperature toughness and corrosion resistance. The surface protection employs a composite process of hot-dip galvanizing and low-temperature protective wax. The zinc layer thickness is ≥100μm, and the protective wax thickness is 20-30μm. The freezing point of the protective wax is ≤-50℃, preventing ice and snow from freezing onto the fishplate surface and isolating it from the corrosion of de-icing agents. During production, the bolt holes of the fishplate are chamfered with a radius of 5mm to prevent frost heave damage caused by ice and snow accumulation in the holes. Simultaneously, the machining accuracy of the fishplate is controlled, with the bolt hole position deviation ≤±0.3mm, ensuring a tight fit with the bolts after installation and reducing the penetration of corrosive media. Furthermore, the protective wax is reapplied to the fishplate annually before winter to ensure protective effectiveness and extend the service life of the fishplate.