Requirements For Uniformity Of Coating

For galvanized steel wire, the requirement for coating uniformity is that the coating is uniform on the transverse (radial) section, and the coating on each cross-section of the steel wire is almost the same in the longitudinal (axial) direction. Local zinc layer accumulation (commonly known as zinc nodules) on the surface of steel wires caused by wire shaking, fluctuation of zinc liquid level, and surface scum in the plating pot should be eliminated through correction of tooling and standardized operation. Without considering these random and irregular zinc layer accumulations, with the determination of tooling, stable process, and the same operating standard, there will not be significant differences in the zinc layers of each section along the entire length of the steel wire. Therefore, a cross-section perpendicular to the steel wire without zinc layer accumulation can be selected for the evaluation of coating uniformity [3].
Measures to improve the uniformity of the galvanized layer on steel wires: The reasons for the uneven coating during the hot-dip coating process of steel wires are: (1) the steel wire is not perpendicular to the zinc liquid surface, so the plating solution brought out during the steel wire introduction cannot flow uniformly along the circumference of the steel wire under its gravity, causing the coating to deviate from the geometric center of the steel wire after solidification; (2) The differences in wiping conditions (such as the size of charcoal particles, the tightness of the contact between charcoal and steel wire, the flow rate and pressure of air friction, etc.) in various directions around the circumference of the steel wire; (3) Fluctuations in the zinc liquid level and wire shaking, as well as floating slag on the surface of the wire; (4) Zinc scraping and uneven deformation of the zinc layer caused by various reasons during the pre plating and post drawing of steel wires. In severe cases, it may even result in the complete loss of the local pure zinc layer.
Measures to be taken: Improve the design and adjust the tooling to ensure that the steel wire positioned by the wire rollers of the pressure shaft and lead out frame is perpendicular to the zinc liquid level. When the pressure shaft wears out, the position of the wire rollers must be adjusted in a timely manner or the pressure shaft must be rotated to ensure that the steel wire is perpendicular to the liquid level. The charcoal particles to be wiped should be uniform and compacted. Zinc addition should be kept away from the outlet and slowly pushed in. The pressure shaft should not be too close to the operating surface of the zinc pot. It is best to have a tension control device on the production line to prevent fluctuations in the zinc liquid level