For those who are purchasing, inspecting the quality of products is very important, and for purchasing stainless steel screws, it is also necessary to know how to detect the quality issues of stainless steel screws. So, what specific methods have everyone learned about how to detect them? Today, the editor will share with you a few points. There are four main inspection methods for stainless steel screw fasteners:

1、 Appearance quality requirements

The inspection of the appearance of stainless steel screws is carried out from various aspects such as appearance, electroplating layer, etc.

2、 Inspection of coating thickness for stainless steel screws

1. Measuring tool method: The amount used includes micrometers, vernier calipers, plug gauges, 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 a magnetic substrate using a magnetic thickness gauge.

3. Microscopic method: Microscopic method, also known as metallographic method, involves magnifying corroded fasteners on a metallographic microscope with a micrometer eyepiece to measure the thickness of the coating on the cross-section.

4. Chronometric flow method

The timed liquid flow method uses a solution that can dissolve the coating to flow onto a local surface of the coating, and calculates the thickness of the coating based on the time required for the local coating to dissolve. There are also coating droplet method, anodic dissolution Coulomb method, and so on.

3、 Inspection of adhesion strength of stainless steel screw coating

There are many methods for evaluating the adhesion between the coating and the substrate metal, usually including the following.

1. Friction polishing test;

2. File method test;

3. Scratch method;

4. Bending test;

5. Thermal shock test;

6. Squeeze method.

4、 Inspection of corrosion resistance of stainless steel screw coating

The inspection methods for corrosion resistance of coatings include:

1. Air explosion and sun exposure test;

2. Salt spray test (NSS test);

3. Acid salt spray test (ASS test);

4. Accelerated acetate spray test (CASS test);

5. Corrosive paste corrosion test (CORR test);

6. Liquid droplet corrosion test;

7. Water immersion test, immersion corrosion test, etc.