The surface treatment process of electrogalvanized steel strips significantly impacts adhesion throughout the entire production process. From cleanliness control in the pretreatment stage to precise matching of electroplating process parameters, and stability maintenance in the post-treatment stage, each step directly determines the bonding strength between the plating layer and the substrate. Incomplete pretreatment will fundamentally weaken the adhesion. In the production of electrogalvanized steel strips, residual oil, scale, or rust on the substrate surface will form a physical isolation layer, hindering the uniform deposition of zinc ions on the substrate surface. For example, on a steel strip surface that has not been thoroughly degreased, the zinc layer may only adhere to the oil film, resulting in locally weak adhesion. Removing oil through alkaline chemical cleaning, solvent cleaning, or ultrasonic cleaning, followed by acid pickling to activate the surface, exposes a clean metal lattice, providing active sites for zinc ion deposition, thereby significantly improving adhesion.
The synergistic effect of the electroplating solution composition and process parameters is a core factor affecting adhesion. The plating baths used for electrogalvanized steel strip typically contain zinc ion sources, conductive salts, buffers, and additives. Excessive use of additives such as brighteners and leveling agents can increase internal stress in the coating, leading to decreased adhesion. For example, in zincate plating, excessive brightener can increase coating brittleness, making edges prone to peeling. Furthermore, the control of current density, temperature, and pH directly affects the zinc ion deposition rate and crystal morphology. Excessively high current density can cause the coating to burn, temperature fluctuations can degrade the plating bath's performance, and a pH deviation from the process range (typically 12-14 for alkaline zinc plating and 4-6 for acidic zinc plating) can disrupt the stability of the deposition reaction, ultimately leading to weakened adhesion.
Post-treatment processes have a crucial impact on the stability of adhesion. After electroplating, electrogalvanized steel strips require passivation treatment to form a dense conversion film on the zinc layer surface to enhance corrosion resistance and adhesion. Colored passivation (such as blue-white or multicolored) can form a hexavalent or trivalent chromium conversion film, whose dense structure reduces the damage to adhesion caused by environmental corrosion. While black passivation or chromium-free passivation (such as molybdate systems) is more environmentally friendly, process optimization is required to maintain adhesion levels. Furthermore, sealing treatment, through filling micropores with special solutions, can further improve corrosion resistance and fingerprint resistance, indirectly strengthening adhesion. If post-treatment is incomplete or improper, the coating is prone to adhesion degradation due to environmental corrosion.
Impurity contamination is a potential risk leading to decreased adhesion. During electroplating, metal oxides, insoluble suspended matter, and organic impurities may mix into the plating bath, disrupting the uniformity of zinc ion deposition. For example, oil stains or brightener decomposition products in the plating bath can form a contaminant layer, creating a "layer" between the coating and the substrate, leading to loss of adhesion. Regularly changing the plating bath, installing a filtration system, and strengthening operator training can effectively control impurity concentration, maintain the purity of the plating bath, and thus ensure stable adhesion. Production pace and process execution intensity also indirectly affect adhesion. In the production of electrogalvanized steel strips, delays in earlier processes may lead to rushed electroplating, potentially shortening plating time or neglecting quality checks, resulting in insufficient plating thickness or adhesion defects. During nighttime operations, insufficient lighting may mask early problems such as plating peeling and blistering, allowing quality issues to spill over into later stages. Optimizing production planning, improving the efficiency of earlier processes, and strengthening quality awareness can prevent adhesion degradation caused by schedule pressure.
Product design rationality is a prerequisite for adhesion. If the design of electrogalvanized steel strip parts does not consider electroplating process requirements, such as complex shapes leading to uneven electroplating solution flow or difficulty in covering internal areas, differences in plating adhesion will occur. The design phase must closely coordinate with the electroplating process to ensure that the part structure meets the requirements of electroplating solution flow and deposition, thereby ensuring uniform adhesion.
Environmental control and equipment maintenance are the foundation for stable adhesion. Temperature, humidity, and cleanliness in the electroplating workshop must be strictly controlled to avoid fluctuations in plating solution performance or secondary contamination of the substrate surface caused by environmental factors. Meanwhile, regular maintenance of electroplating equipment to prevent impurities from seeping in due to poor sealing can ensure the continuous stability of process parameters, thereby maintaining the long-term reliable adhesion of the plating layer.
