Detecting the zinc coating thickness of galvanized coils requires a combination of non-destructive and destructive methods. The appropriate technology should be selected based on the testing objective (e.g., production quality control, arbitration, or R&D analysis). The following is a systematic summary of mainstream testing methods:
Non-destructive Testing Methods (Suitable for Rapid On-Site Testing)
1. Magnetic Thickness Measurement: Suitable for ferrous-based galvanized materials. It uses a magnetic probe to measure the difference in magnetic permeability between the zinc coating and the steel substrate, quickly obtaining the thickness value.
- Advantages: Simple operation, non-destructive, real-time readings, suitable for online production line testing.
- Precautions: Calibration with a standard sheet is required before measurement; avoid measuring on edges, welds, or rough areas; take at least 5 points on each measurement surface and calculate the average value to improve accuracy.
2. Eddy Current Thickness Measurement: Based on the principle of high-frequency electromagnetic induction, suitable for measuring non-conductive or weakly conductive coatings on conductive substrates.
- Applicable Scenarios: Can be used to detect galvanized coatings on non-ferrous metal substrates such as copper and aluminum, but is also effective on steel substrates.
- Advantages: Can measure minute areas and curved surfaces, suitable for edge inspection of complex-shaped galvanized coils.
3. X-ray Fluorescence (XRF) : This method generates characteristic X-rays by exciting zinc, and the thickness is estimated based on the fluorescence intensity.
- Advantages: Non-destructive, capable of measuring multilayer structures (such as passivation film + zinc layer), and can simultaneously analyze the composition of the zinc layer.
