1. Appearance quality requirements

1. Measuring tool method

2. Magnetic method

The magnetic method to measure the thickness of the coating layer is a non-destructive measurement of the non-magnetic coating layer on the magnetic substrate with a magnetic thickness gauge.

3. Microscopy

4. Timing sap flow method

3. Inspection of the adhesion strength of the screw coating

1. Friction and polishing test ; 2. File method test ; 3. Scratch method ; 4. Bend test ; 5. Thermal shock test ; 6. Extrusion method.

4. Inspection of corrosion resistance of screw coating

The coating corrosion test methods include : atmospheric exposure test ; neutral salt spray test (NSS test ); acetic acid salt spray test (ASS test ) , copper accelerated acetic acid salt spray test (CASS test ); and corrosion paste corrosion test (CORR test ) and solution spot corrosion test ; immersion test, inter-immersion corrosion test and so on.