Q:How to choose the coating type in different environments?
A:Highly corrosive environment (C5-M): zinc-aluminum-magnesium coating (30μm+) is preferred, and its corrosion resistance is 5~10 times that of pure zinc.
Medium corrosive environment (C3-C4): hot-dip galvanizing (25~80μm) + chromium-free passivation + primer, the service life can reach 15~30 years.
Q:How to extend the service life of galvanized steel?
A:Surface treatment enhancement
Passivation process: Chromium-free passivation increases service life by 10%~30%, which requires compensation for coating thickness.
Coating superposition: Applying fluorocarbon topcoat on zinc-aluminum-magnesium coating can extend service life to more than 25 years in C5-M environment.
Processing and maintenance
Damage repair: The cut edge is repaired with zinc-rich paint (zinc content ≥ 90%), which can restore more than 90% of the protective performance.
Regular inspection: Use a coating thickness gauge to monitor the remaining thickness of the coating, and re-coat it in time when it is below the critical value.
Q:Can the thickness of the galvanized layer directly affect the service life?
A:The thickness of the galvanized layer is one of the key factors that directly affect the service life. Its working principle is closely related to the intensity of environmental corrosion. The core function of the galvanized layer is to act as a physical barrier to prevent corrosive media (such as water, oxygen, salt, acid, etc.) from directly contacting the steel substrate. The greater the thickness, the longer it takes for the corrosive media to penetrate the coating and reach the substrate, and the longer the service life.
Q:What post-treatment processes can improve the corrosion resistance of the zinc coating without increasing its thickness?
A:1. Passivation treatment: a protective film is formed by chromate (or chromium-free passivation agent) to inhibit electrochemical corrosion.
2. Sealing treatment: an organic coating (such as resin) or silane is applied to fill the pores of the coating and enhance isolation.
3. Thermal diffusion treatment: such as aluminum infiltration and silicon infiltration to form a corrosion-resistant alloy layer to improve the ability to resist high temperature and chemical corrosion.
4. Coating alloying: zinc-nickel, zinc-iron and other alloy coatings are used, and the corrosion resistance is better than that of pure zinc layer. 5. Organic coating coverage: electrophoretic paint, epoxy coating and other physical isolation of corrosive media.
6. Nano coating technology: spraying nano materials such as graphene and silicon dioxide to form an ultra-thin high protective layer.
Q:What impact does galvanizing thickness measurement have on costs?
A:The thickness of galvanized steel is nonlinearly positively correlated with the cost, and a balance needs to be found between the corrosion resistance requirements and economic efficiency. Priority should be given to optimizing the coating material (alloying), process (hot-dip coating instead of electroplating) and post-processing technology to control the thickness while meeting the performance requirements, rather than simply relying on thickening the coating to reduce costs.