What are the inspection methods for precision hardware parts screws?

What are the inspection methods for precision hardware parts screws? There are two types of surface inspection for screws: one is the inspection before electroplating after the screws are produced, and the other is the inspection after electroplating, which means the inspection after the screws are hardened and the screw surface is treated. After the screws are produced and before electroplating, we conduct inspections on dimensions, tolerances, and other aspects of the screws.

Check if it meets national standards or customer requirements. After the surface treatment of the screws, we inspect the electroplated screws, mainly for the color of the plating and whether there are any damaged screws. This way, when we send the screws to the customer, they can smoothly pass the customs when they receive the goods. Inspection after screw treatment:

1、 Appearance quality requirements
The inspection of screw appearance is carried out from various aspects such as appearance, electroplating layer, etc.

2、 Inspection of screw coating thickness

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. Timing liquid flow method: The timing liquid flow method uses a solution that can dissolve the coating to flow onto the 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 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 screw coating
The inspection methods for corrosion resistance of coatings include: atmospheric explosion test; Neutral salt spray test (NSS test); Acetate spray test (ASS test), copper accelerated acetate spray test (CASS test); And corrosion paste corrosion test (CORR test) and solution droplet corrosion test; Immersion test, inter immersion corrosion test, etc.