1.How to optimize welding process?
The key to reducing burn-in loss at the source is to select appropriate welding methods and parameters to reduce the damage to the zinc layer caused by heat input.
Optimize welding parameters.
Reducing heat input: Reduce welding current and shorten welding time (for example, reducing the resistance spot welding current from 10kA to 8kA reduces welding time from 20ms to 15ms).
Controlling the arc/laser focus: Avoid directly burning the zinc layer, slightly shifting the focus toward the base material (steel) to minimize zinc evaporation.
Using zinc-based filler material: For MIG welding, use zinc-containing wire (such as Zn-Al alloy wire) to replenish zinc during welding and minimize zinc loss in the burned area.
2.How to protect before welding?
Applying a high-temperature protective agent
Material selection: Use a high-temperature resistant coating (temperature resistance ≥ 300°C) containing aluminum powder and ceramic particles, or a specialized zinc protective adhesive (such as silicone).
Application: Before welding, apply the agent evenly within a 5-10mm radius on both sides of the weld to form a thin film. This can be left on or removed after welding (depending on subsequent processing requirements) to effectively protect the zinc layer from oxygen.
Local shielding protection
Inert gas shielding: For laser welding, TIG welding, and other processes, introduce argon or nitrogen around the weld to create a localized inert atmosphere and reduce zinc oxidation.
Physical shielding: Use copper or ceramic sheets to cover the zinc layer in the non-welding area near the weld to block high-temperature radiation (suitable for manual welding).
3.How to repair the burned zinc layer?
Zinc Repair Coating (Cold Spray Zinc)
Principle: Composed of high-purity zinc powder (content ≥95%), resin, and solvent, it forms a zinc layer upon application, which synergistically protects against corrosion with the original zinc layer.
Steps:
Cleaning the weld area: Use sandpaper or a wire brush to remove weld slag and scale to expose a clean metal surface.
Applying cold spray zinc: Maintain a dry film thickness of 60-80μm, ensuring coverage of the burned area and the surrounding 2-3mm of original zinc layer to create a continuous protective barrier.
Curing: Allow to dry at room temperature for 24 hours, or heat (60°C) for accelerated curing.
Thermal Spraying of Zinc/Zinc-Aluminum Alloy
Applications: For outdoor components with high corrosion protection requirements (such as photovoltaic racks and bridge connectors) and large burnt areas.
Process: Using arc spraying or flame spraying, a zinc wire (99.9% purity) is melted and sprayed onto the weld area at high speed, forming a zinc layer 80-150μm thick. This layer bonds tightly to the original zinc layer, providing an anti-corrosion lifespan comparable to that of the original galvanized layer.
Zinc-Chromium Coating (Dacromet Treatment)
Features: A water-based coating containing zinc flakes and chromates, curing at low temperatures (below 200°C), making it suitable for applications where high-temperature treatment is not feasible.
Advantages: Uniform coating and excellent salt spray resistance (over 500 hours). However, the cost is relatively high, making it suitable for high-end equipment.
4.What other auxiliary measures are there?
Rapid cooling after welding: Use compressed air or cold water spray to cool the weld area, shortening the zinc layer's exposure to high temperatures and reducing oxidation.
Design optimization: Place welds on non-exterior surfaces or in high-maintenance areas to facilitate subsequent repairs. Use sealants (such as silicone) for secondary protection in key areas to isolate them from moisture.
5.How to combine "prevention + repair" for zinc layer protection in galvanized sheet welding area?
Prioritize low-heat welding to minimize burnout, using heat-resistant coatings or inert gas shielding. Repair zinc defects promptly after welding using cold or hot zinc spraying, supplemented by sealing measures if necessary. Choosing the appropriate solution based on the application scenario (e.g., indoor appliances vs. outdoor photovoltaics) can significantly extend the corrosion life of the weld area.