Q:How to choose coating thickness for galvanized steel?
A:1. Determine the corrosion level of the application scenario.
2. Check industry standards to clarify the minimum thickness requirements.
3. Evaluate the substrate thickness, shape and processing technology (such as welding, stamping).
4. Combined with the service life requirements, select the galvanizing process (electrogalvanizing/hot-dip galvanizing/alloy coating).
5. Ensure that the coating thickness uniformity and adhesion meet the standards through testing.
Q:What are the methods for testing coatings?
A:Magnetic thickness gauge: non-destructive testing, suitable for rapid on-site measurement.
Weighing method: convert thickness by unit area mass of coating (g/m²) (1μm zinc ≈ 7.14g/m²).
Microscope method: destructive testing, used for arbitration or precision testing.
Q:What are the coating selection requirements for automotive parts?
A:Body frame (indoor environment): electrogalvanizing or hot-dip galvanizing, thickness 5~12μm.
Chassis parts (outdoor, salt spray environment): hot-dip galvanizing or alloy plating (such as zinc-nickel), thickness 15~25μm, passivation process (such as chromium-free passivation) is required to improve salt spray resistance (≥500 hours).
Q:What are the requirements for galvanized steel coating on fasteners such as bolts and nuts?
A:General use (indoor): electrogalvanizing 6~12μm, passivation required (such as blue-white zinc, yellow zinc). Outdoor or high-strength bolts: hot-dip galvanizing 25~35μm, or Dacromet coating (chromium-free zinc-chromium coating, thickness 8~12μm, salt spray resistance ≥1000 hours).
Q:What effect does the substrate have on galvanized steel coatings?
A:Substrate thickness: Thick steel plate (e.g. ≥6mm): The hot-dip galvanized layer can be slightly thicker (e.g. ≥85μm) to ensure the bonding strength between the coating and the substrate.
Thin steel plate (e.g. ≤2mm): The coating thickness needs to be controlled (e.g. ≤20μm) to avoid excessive thickening that affects assembly accuracy (e.g. stamping parts, bending parts).
Parts with complex shapes: holes, grooves and other parts are prone to thinning of the coating, and the average thickness needs to be increased (such as 30%~50% thicker than flat parts), or hot-dip galvanizing is used (the uniformity of the coating is better than electro-galvanizing).
