About Electroplating Of Cold Heading Riveting Studs

A cold-headed standoff, a class of pointed, nail-ended, threaded parts on small cylindrical or conical metal rods, having a grooved or dimpled head, used alone. Next, Hongrui will tell you about the electroplating of cold heading and riveting studs. Electroplating is the process of plating a thin layer of metal or alloy on the surface of certain metals by using the principle of electrolysis. It is a technology that uses electrolysis to attach a layer of metal film to the surface of metal or other material parts and then It can prevent corrosion, improve wear resistance, conductivity, reflectiveness and enhance beauty. The quality of electroplating of pressure riveting fasteners is mainly measured by its corrosion resistance, followed by appearance. Corrosion resistance is to imitate the working environment of the product, set it as the test condition, and conduct a corrosion test on it.

     The quality of electroplating products is controlled from the following aspects:

1. Appearance: The surface of pressure riveting fastener products is not allowed to have some uncoated, burnt, rough, dull, peeling, crusting and obvious stripes, and pinhole pitting, black slag, and passivation film are not allowed Porosity, cracks, drops and severe passivation marks.

2. Coating thickness: The working life of pressure riveting fasteners in a corrosive atmosphere is directly proportional to its coating thickness. The thickness of the economical electroplating coating usually recommended is 0.00015in～0.0005in (4～12um).

        Hot-dip galvanizing: the standard average thickness is 54 um (43 um for appellation diameter ≤ 3/8), and the minimum thickness is 43 um (37 um for appellation diameter ≤ 3/8).

3. Coating distribution: different accumulation methods are used, and the collection methods of the coating on the surface of the fastener are also different. During electroplating, the plated metal is not evenly deposited on the outer periphery, and a thicker plated layer is obtained at the corner. On the thread part of the fastener, the thickest coating is located on the crest of the thread, gradually thins along the circumference of the thread, and accumulates the thinnest at the bottom of the tooth, while hot-dip galvanizing is just the opposite, and the thicker coating is deposited on the inner corner As with thread bottoms, mechanical plating has the same tendency to deposit metal as hot-dip plating, but is smoother and much more uniform in thickness over the entire surface. Pressure riveting stud

4. Hydrogen embrittlement: During the processing and treatment of pressure riveting fasteners, especially during the pickling and alkali cleaning before plating and the subsequent electroplating process, the surface absorbs hydrogen atoms, and the accumulated metal coating then captures hydrogen. As the fastener is tightened, the hydrogen moves toward the point where the stress Z is concentrated, causing the pressure to increase beyond the strength of the base metal and cause microscopic surface fractures. Hydrogen is extraordinarily mobile and quickly enters newly formed fissures. This stress-crack-entry cycle continues until the fastener cracks. Onset usually occurs within a few hours of initial stress application.