The quality judgment of fastener electroplating layer - Hydrogen embrittlement
Hydrogen embrittlement
Fasteners in the processing and treatment process, especially in the plating before the pickling and alkaline cleaning and subsequent plating process, the surface absorbed hydrogen atoms deposited in the process of hydrogen generation. When the fastener is tightened, hydrogen towards the most concentrated part of the stress transfer, causing the pressure to increase to more than its strength and produce a small surface rupture, hydrogen infiltration into the newly formed fissures. This cycle of stress-rupture-infiltration continues until the fastener breaks. This usually occurs within a few hours of the first stress application. To eliminate the threat of hydrogen embrittlement, fasteners are heated and baked within 3 hours of plating to allow hydrogen to seep out of the plating, usually at a temperature of about 200°C, with the duration of treatment determined by their required tensile strength.
Because mechanical galvanizing is non-electrolytic, which virtually eliminates the threat of hydrogen embrittlement, hydrogen embrittlement rarely occurs with hot-dip galvanized fasteners.