Stainless steel screws are widely used. When buying stainless steel screws, pay attention to the detection. There are many aspects of stainless steel screw detection. For example, the head of the stainless steel screw is tested to see if the stainless steel screw is headshot. There is also the detection of various sizes of stainless steel screws. See if it meets the national standard or the size required by the customer. Then Yaqing will introduce the main detection methods for stainless steel screws:

 

 

   1. Inspection of screw plating thickness

 

   1. Gage method: the amount used is 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. Microscope method: The microscope method is called the metallographic method, which is to enlarge the etched fasteners on a metallographic microscope with a micrometer eyepiece to measure the thickness of the coating on the cross section.

 

   4. Chronoflow method: Chronoflow method is to use a solution that can dissolve the plating layer to flow on the local surface of the plating layer, and calculate the thickness of the plating layer according to the time required for the local plating layer to dissolve. There are also plating drip method, anode dissolution coulomb method and so on.

 

 

   Second, the appearance quality requirements

 

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

 

 

   3. Inspection of corrosion resistance of stainless steel screw plating

 

   The test methods for corrosion resistance of the coating are: atmospheric explosion test; neutral salt spray test (NSS test); acetate salt spray test (ASS test), copper accelerated acetate salt spray test (CASS test); and corrosion paste corrosion test (CORR test) and solution drip corrosion test; dipping test, interdip corrosion test, etc.

 

 

   4. Inspection of the adhesion strength of the screw plating

 

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

 

   1. Friction polishing test;

 

   2. File method test;

 

   3. Scratch method;

 

   4. Bending test;

 

   5. Thermal shock test;

 

   6. Extrusion method.