1. Coating thickness
The service life of a screw fastener is closely related to its coating thickness. Plating thickness is the primary indicator to measure plating quality, the general recommendation of economic plating coating thickness is 4 ~ 12μm. For hot-dip galvanizing, the standard average thickness is 54μm (43μm when the nominal diameter is ≤3/8) and the minimum thickness is 43μm (37μm when the nominal diameter is ≤3/8).
2. Appearance quality
The appearance of the electroplated product is equally important. The surface of screw products should have no local no coating, burnt, rough, gray, peeling, crust and obvious stripes. At the same time, it is also necessary to avoid pinhole pitting, black plating slag, passivation film loose, cracking, falling off and serious passivation marks, these defects will directly affect the beauty of the product and the use of performance.
Third, hydrogen embrittlement control
Hydrogen embrittlement is a problem that needs strict control during electroplating. During the pre-plating treatment and electroplating process, the surface of the fastener will absorb hydrogen atoms, resulting in small surface cracks when tightened. Therefore, effective measures must be taken to reduce the risk of hydrogen embrittlement and ensure the safety of fasteners.
Fourth, coating distribution uniformity
The distribution of coating is also a key factor affecting the quality of electroplating. During plating, the distribution of the coated metal on the surface of the fastener may be uneven, and the thickness of the coating at the corner and the thread part will be different. Hot dip galvanizing and mechanical plating have different coating distribution characteristics, and it is necessary to choose the appropriate plating method according to the specific needs, and ensure that the coating is as uniform as possible on the entire surface.
