info@pdmindustry.comMetal screw fasteners, electroplating to master the quality2018-06-19
Electroplating is a common way hardware fastener products surface treatment such as screws, under normal circumstances, the quality of the plating to its corrosion resistance ability as the main measure, the second is the appearance. Corrosion resistant ability is imitation products work environment, is set to the test conditions, corrosion test them. Screw hardware plating quality control from the following aspects:
1, appearance: hardware screws products surface are not allowed to have a local without coating, burning, rough, dark, peeling, the condition of crust and stripes obviously, there is no pinhole pitting, black plated slag, passivation membrane loose, crack, fall off and the serious passivation.
2, hydrogen embrittlement: hardware screw fasteners in the process of machining and processing, especially in the acid and alkaline cleaning before plating and subsequent electroplating process, the surface absorbed hydrogen, deposition of metal coating and then capture hydrogen. When the fastener tighten, hydrogen turn towards the part of the most concentrated stress enough, cause the pressure increased to more than the strength of the matrix metal and generate small surface rupture. Hydrogen special events and quickly penetrate into the newly formed fractures.
3, coating distribution: using different methods of deposit and the coating on the surface of fasteners on the way is different also. When screw fasteners hardware plating coating metal is not evenly deposit weeks out on the edge, corner to get thicker coating. In fasteners, threaded portion, the thickest deposit is located in the top thread, along the thread profile gradually thinning, the thinnest the sedimentation of the tooth to ascend, and the opposite of hot dip galvanized, thicker coating deposition, corner and the bottom of the thread, the mechanical plating coating metal deposition tendency of the same as the hot dip plating, but more smooth and thickness is much more evenly across the surface.
4, coating thickness: hardware screw fasteners in the operation life of corrosive atmosphere and its coating thickness is proportional to the. General recommendation economy plating coating thickness is 0.00015 ~ 0.0005 in (4 ~ 12 um) in hot dip galvanizing: standard of the average thickness of 54 um (43 um call diameter 3/8 or less), the minimum thickness of 43 um (37 um call diameter 3/8 or less).
