Hot-dip galvanizing coating quality defects
1. Dark coating
It is in patchy or reticular shape. The coating in the gray and dark areas is all Zn-Fe alloy. The steel alloy layer containing about 0.1% and more than 0.3% silicon grows very fast. Before water cooling, the alloy layer has grown to the surface of the zinc layer and loses its metallic luster. The appearance of the gray coating is ugly, but it has no impact on the coating's resistance to atmospheric corrosion.
2. Missing plating
Residual paint, grease, oxide scale, welding slag and rust spots that cannot be removed by normal pickling, or interlayers, non-metallic inclusions, etc., when the diameter is less than 2mm, will not affect the corrosion resistance. The size of the area allowed for repair, the proportion of the total area and the repair method are in accordance with product-related standards.
3. Dust is stuck on the surface
The particulate zinc protrusions contain particles of zinc-coated zinc slag FeZn13 (containing 6% Fe), which does not affect the corrosion resistance.
4. Oxide film marks
Phenomenon: Slight oxide film marks on the surface of the plated parts.
Causes: lack of aluminum; pause during lifting of plated parts or improper method of removing zinc dust.
Treatment measures: No treatment is required, but it should be avoided by adjusting the zinc solution and removing dust correctly.
5. white rust
Phenomenon: Plated parts produce a large amount of white corrosion products due to incorrect stacking or storage conditions.
Cause: In a humid environment with poor air circulation, new plated parts are packed before being dried.
Yifa products: plates, angle steel, pipe fittings, etc.
Treatment measures: The surface of the plated parts should be clean and free of moisture and other residues, and should be stored in a dry and ventilated environment. The packaged parts should avoid contact with the ground, and leave appropriate gaps between parts.
6. Hang zinc
Phenomenon: Zinc or zinc tumors hang on the tail of the workpiece.
Reasons: The lifting angle of the plated parts is not enough, the lifting speed is too fast, the defects are not scraped in time when the plated parts are out of the pot, or the three-dimensional structure is difficult to eliminate.
Treatment measures: file, grind and trim.
