Electroplating is one of the most common fastener processing processes. It uses electrolysis to attach a metal film to the surface of the fastener, thereby improving the wear resistance, anti-corrosion, and aesthetics of the fastener. It can also be used according to the different plating layers. Improve conductivity, lubricity, heat resistance, hardness, etc.
Whether fastener electroplating is qualified or not depends on four aspects: appearance, coating thickness, coating distribution, and whether there is hydrogen embrittlement.
Appearance after electroplating
The appearance of the fasteners after electroplating must meet the following requirements: no partial plating, burnt, rough, gray, peeling, crusting conditions and obvious streaks. At the same time, there should be no pinhole pitting, black plating slag, or cracks. , falling off, loose passivation and severe passivation marks.
Coating thickness
The coating thickness of fastener electroplating is directly proportional to its anti-corrosion property. Considering economics, the coating thickness is mostly 4-12 μm. The average thickness of hot-dip galvanizing is 54 μm, and the minimum thickness is 43 μm.
Coating distribution
The plating distribution of fasteners is different, and their deposition methods and accumulation methods are also different. During electroplating, the coating is not uniformly deposited on the peripheral edge, and the coating will be thicker at the corners; in the threaded part, the thickest coating is on the top of the thread, and will gradually become thinner along the side of the thread, and the coating will be thicker at the bottom of the thread. The thinnest. If it is a hot-dip galvanized coating, its distribution is opposite to that of electroplated coating.
Whether there is hydrogen embrittlement
Qualified electroplating processing will not cause hydrogen embrittlement. In order to prevent hydrogen embrittlement, threaded fasteners should be heated and baked as quickly as possible after electroplating to allow hydrogen to seep out of the coating, so that the fasteners will not become hydrogen embrittled and break.
