A few days ago, we divided the analysis of the surface defects of hot-dip galvanized punching nets. Today we will share with you the analysis of the defects of electro-galvanized punching nets.
Similar to the production process of hot-dip galvanized sheet, the production process of electro-galvanized sheet is also divided into two steps: pre-treatment (cleaning section) and post-plating treatment. The quality of electrogalvanized sheets depends to a large extent on the quality of the wash before plating. The main purpose of electro-galvanizing post-treatment is to improve the surface coating performance and corrosion resistance of galvanized sheets to extend the service life of galvanized sheets. Post-plating treatment mainly includes phosphating and chromizing. In addition to the original board defects, any one of the procedures is not properly operated, which will cause quality problems. Typical surface defects are:
1. Pitting point: refers to the irregular cavity hole on the surface of the coating, which is characterized by different shapes, sizes and shades. Pitting is generally a defect due to substrate defects or foreign matter sticking during plating.
2. Glitch: A foreign object with a raised surface and a stinging sensation, which is usually characterized by electroplating upward or high current density. The thickness of the zinc layer of electrogalvanized is controlled by controlling the current density and the strip speed, that is, increasing the current density and lowering the strip speed can increase the thickness of the zinc layer. However, there is a limit. When the strip speed is low and the current density is high, the surface of the coating will become rough, which will affect the quality of the coating.
3. Pinhole: The pores on the surface of the coating are similar to those of the needle tip. The density and distribution are not the same, but when viewed under a magnifying glass, the size and shape are generally similar. Pinholes are typically defects caused by hydrogen bubble adsorption during electroplating. In the electroplating reaction, a large number of bubbles are generated. If these bubbles are not removed in time, they are retained between the surface of the strip and the anode. The surface of the anode and the strip are covered by the gas layer to affect the conduction, causing partial plating on the surface of the strip.
4. Spot: defects such as spots and dark spots on the surface of the coating. It is caused by poor deposition of metal ions in the plating process, adhesion of foreign matter or passivation of the passivation solution after passivation treatment.
5. Yin and Yang surface: the defects of partial brightness or uneven color on the surface of the coating. In most cases, it shows certain regularity in similar products.
6. Partially uncoated: defects in the surface area of the coating, such as leakage plating, iron spot or point defects (except for process regulations).
7. Peeling: Cracked or non-cracked defects in the plating and punching stencil peeling. Usually caused by poor pre-plating treatment.