1.What are the core principles?
The goal is to remove zinc oxide particles while protecting the intact paint coating to the greatest extent possible. Absolutely avoid using harsh methods that could scratch or dissolve the paint film.
2.What measures can be taken before welding?
Pre-grinding of the welding area: Lightly grind the area approximately 20-30mm on both sides of the weld seam using a scouring pad or very fine sandpaper (e.g., 400# or higher) to remove the color coating and part of the zinc layer, exposing the metal substrate. This is the most effective and recommended method.
Applying welding anti-spatter agent: Spray a special anti-spatter agent onto the coating on both sides of the weld seam to form a protective film, preventing zinc mist from adhering and making it easy to wipe off after completion.
Using specialized welding materials and processes:
Selecting low-soot welding rods/wires: Such as flux-cored wire, which reduces zinc evaporation.
Controlling welding parameters: Using a lower current and a faster welding speed reduces heat input.
Improving welding technique: Tilting the welding torch backward (dragging method) allows the arc force to push the slag and zinc vapor towards the exposed area behind.
3.How can zinc fog with a noticeable grainy texture be physically scraped off?
Tools: Use a plastic scraper, wooden scraper, or a dedicated brass scraper. These metals are softer than the pre-coated steel sheet and will not scratch the intact coating.
Method: Gently scrape away the raised zinc oxide particles at a small angle (almost parallel to the surface of the sheet). Never use steel blades or hard scrapers.
4.What are the brushing and cleaning steps?
Tools: Use a dry, soft nylon brush (such as a paintbrush) or a scouring pad (green, rough side) to gently brush in the same direction.
Purpose: To remove loose powder. Then wipe the area with a clean, damp cloth (you can use water or a neutral detergent solution) to remove any residue.
Caution: Avoid scrubbing vigorously in a circular motion to prevent spreading the hazy residue.
5.What practices are absolutely prohibited?
Do not use steel wool or steel wool: These will severely scratch the coating, leading to widespread corrosion.
Do not use strong acids (such as concentrated hydrochloric acid) for direct wiping: These will completely corrode the zinc layer and coating.
Do not use heavy abrasives (such as coarse grinding wheels): Unless you plan to repaint the entire area.
Do not neglect repairs: Cleaning without repairs is equivalent to only "surface beautification," and the anti-corrosion properties are lost, allowing rust to begin from that point.