Four inspections of stainless steel screws after treatment

In order to meet customer requirements, many manufacturers process stainless steel screws, which can not only meet customer requirements, but also improve the performance of stainless steel screws, so that customers can use them with confidence. And for the processed stainless steel screws, in order to verify whether the stainless steel screws are suitable, which aspects should be tested? The tests are mainly conducted from four aspects.

1. Appearance quality requirements

The inspection of the appearance of stainless steel screws is carried out from the appearance, plating layer and other aspects.

Second, the inspection of the thickness of the screw coating

1. Measuring tool method: The amount used includes micrometer, vernier caliper, plug gauge, etc.

2. Magnetic method: The magnetic method measures the thickness of the coating layer, which is a non-destructive measurement of the non-magnetic coating layer on the magnetic substrate with a magnetic thickness gauge.

3. Microscopy: the microscopy method is called metallographic method, which is to magnify the etched fasteners on a metallographic microscope with a micrometer eyepiece to measure the thickness of the coating on the section.

4. Timing flow method (Guide: Knowledge of stainless steel fastener material)

The chronograph flow method is to use a solution that can dissolve the coating on the partial surface of the coating, and calculate the thickness of the coating according to the time required for the partial coating to dissolve. There are also plating spot method, anode dissolution coulometric method and so on.

3. Inspection of the adhesion strength of the screw coating

There are many methods to evaluate the adhesion of the coating to the base metal, usually the following.

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

IV. Inspection of corrosion resistance of stainless steel screw coating

The corrosion resistance test methods of the coating 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, etc.

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