Q:How to measure the thickness of the zinc coating?
A:1. Magnetic thickness measurement method (most commonly used)
Principle: Using the principle of magnetic induction or eddy current, the thickness difference between the non-magnetic zinc layer and the magnetic steel substrate is measured by a probe.
Advantages: Fast, non-destructive, suitable for on-site detection.
2. Metallographic microscope method (high precision)
Steps: Cut the sample → Inlay and polish → Observe the cross section with a microscope → Measure the thickness of the zinc layer with software.
Advantages: Accurate results, suitable for laboratory arbitration detection.
3. Dissolution weighing method
Steps: Dissolve the zinc layer with hydrochloric acid → Weigh the weight difference before and after dissolution → Calculate the thickness (based on zinc density and area).
Applicable scenarios: Simple measurement when there is no equipment, but the sample is destroyed.
Q:How to judge the uniformity of the galvanized layer?
A：1. Visual inspection: Observe whether there are obvious defects such as color difference, missing plating or zinc nodules on the surface.
2. Multi-point measurement with magnetic thickness gauge: Select different positions of the plate (such as four corners plus the center) to detect the thickness, and the deviation is ≤15% to be considered qualified.
3. Copper sulfate test (quick verification): No red copper plating is precipitated after immersion, indicating that the zinc layer is evenly covered.
Q：What should I do if the zinc layer cracks after the galvanized sheet is bent?
A：1.Appropriately increase the bending temperature or reduce the bending speed to reduce the stress of the zinc layer.
2.After cleaning the cracks, spray zinc-rich paint or cold galvanize to repair.
Q：Is the appearance of white rust on the surface of the galvanized layer considered unqualified?
A：1.Slight white rust (local, not penetrating the zinc layer): usually a temporary phenomenon, no substrate corrosion after wiping is acceptable;
2. Severe white rust (large area, accompanied by zinc layer shedding): indicates that the anti-corrosion performance has decreased and needs to be scrapped or repaired (such as paint protection).
Q：How to repair the zinc coating leakage or nodules?
A：Repair of missed plating: Grind the missed plating area → Spray cold galvanizing (containing zinc ≥ 96%) or hot spray zinc → Test thickness/adhesion.
Nodule treatment: Grind light nodules flat; Heat and scrape off heavy nodules → Repair with zinc.