How to Precisely Control the Hot-Dip Galvanizing Process to Improve Corrosion Resistance in the Manufacturing of Angle Steel Towers?
Publish Time: 2025-11-07
In the construction of infrastructure such as power, communication, and transportation, angle steel towers, as important metal support structures, are exposed to complex and changing natural environments for extended periods, making them highly susceptible to corrosion. To extend their service life and ensure structural safety, hot-dip galvanizing is currently one of the most commonly used and efficient anti-corrosion methods. However, if the hot-dip galvanizing process is not properly controlled, it will not only fail to effectively prevent corrosion but may also cause problems such as coating peeling, incomplete coating, and zinc nodules. Precisely controlling each key step of the hot-dip galvanizing process is crucial to improving the overall corrosion resistance of angle steel towers.
1. Pre-treatment Stage: Laying the Foundation for Coating Adhesion
70% of the quality of hot-dip galvanizing depends on the effectiveness of the pre-treatment. Before entering the zinc bath, angle steel tower components must be thoroughly cleaned of surface oil, scale, and rust. This typically involves a three-step process: degreasing, pickling, and fluxing. Degreasing requires selecting alkaline or solvent-based cleaning agents based on the type of grease, and strictly controlling temperature and time. Pickling typically uses hydrochloric acid or sulfuric acid, with appropriate concentration and immersion time to avoid excessive corrosion of the base metal due to over-acidification. The fluxing stage uses zinc ammonium chloride solution to form a protective film, preventing re-oxidation of components before galvanization. Each step requires thorough rinsing with water to prevent impurities from interfering with subsequent galvanizing reactions.
2. Hot-dip galvanizing process: Precise control of process parameters
The core of hot-dip galvanizing lies in the coordinated control of zinc bath temperature, immersion time, and pull-out speed. The zinc bath temperature is generally maintained between 440–460℃. Too high a temperature will result in an excessively thick and brittle iron-zinc alloy layer, while too low a temperature will result in poor fluidity and potential incomplete galvanizing. The immersion time of the component in the zinc bath should be adjusted according to its thickness, typically 3–5 minutes, to ensure sufficient reaction and the formation of a dense coating. The pull-out speed must be smooth and uniform; too fast a speed can easily form zinc nodules or runs, while too slow a speed will result in an excessively thick coating, increasing costs and increasing the risk of cracking. In addition, the composition of the zinc bath needs to be tested regularly, controlling the iron content to below 0.07%, and ensuring that the content of impurities such as lead and aluminum meets national standards to guarantee the purity and adhesion of the coating.
3. Post-treatment and Inspection: Ensuring a Closed-Loop Quality Process
After galvanizing, the components must be cooled immediately, usually by air or water. However, the water used for cooling should be clean to prevent chloride ions from corroding the new coating. Passivation treatment is then performed to further delay the formation of white rust. Finished products must be inspected for appearance, thickness, adhesion, and uniformity according to standards. Coating thickness generally requires hammer and bending tests to verify the bonding strength between the coating and the substrate. For large angle steel tower components, batch sampling and record traceability are also required to achieve full-process quality control.
4. Management and Technology Upgrades: Driving Continuous Process Optimization
In addition to process control, enterprises should establish comprehensive hot-dip galvanizing operation instructions and personnel training mechanisms to ensure standardized operations. Simultaneously, the introduction of intelligent equipment such as automated hoisting systems, online temperature measuring instruments, and zinc bath composition analyzers can significantly improve process stability. In recent years, the application of green technologies such as chromium-free passivation and environmentally friendly fluxing agents has reduced environmental impact while ensuring corrosion resistance.
In summary, the improved corrosion resistance of hot-dip galvanizing on angle steel towers relies on precise control throughout the entire process, from pretreatment to post-inspection. Only by organically combining materials, processes, equipment, and management can a durable, reliable, cost-effective corrosion protection system be created, providing a solid guarantee for the safe operation of major national infrastructure.
