1. What should you do immediately if you find galvanized coils have become damp and rusty?
First, you need to assess the severity of the rust before taking any action. If only water has entered the packaging or there is a very slight white powder on the surface, the most urgent thing to do is to immediately remove the packaging and spread the galvanized coils out in a well-ventilated area to air dry naturally. After drying, the white rust powder can be removed by wiping with a dry cloth. During this process, please be careful not to use a wire brush or coarse sandpaper to scrub vigorously, as this may damage the zinc layer. For slight white rust, there is a special case: the zinc hydroxide in mild white rust will react with the air after ventilation, transforming into basic zinc carbonate, which has a protective effect. In this case, it may not even be necessary to wipe it off.
2.What if the white rust is severe and cannot be removed by simply wiping with a dry cloth?
For moderate to severe white rust, a more proactive approach is needed. You can use a stiff nylon brush or fine sandpaper (1200 grit or higher recommended) to gently brush away the surface rust powder. If the rust is stubborn, you can also use a mild acidic solution for chemical treatment. Mix edible white vinegar and water in a 1:3 ratio, apply it to the rust, leave it for 5 to 10 minutes, then scrub with a soft-bristled brush. Finally, rinse thoroughly with plenty of water and allow to dry completely.
3.What should I do if the galvanized layer has severely peeled off, exposing the underlying steel and causing red rust?
Once red rust is found, it indicates that the zinc layer has been deeply corroded, and the situation is quite serious. Simple wiping will not be effective. First, thoroughly sand away the red rust and surrounding damaged zinc layer with fine sandpaper. Then, use a cold-spray zinc repair paint containing high-purity zinc powder to repair the area, ensuring complete coverage after repair.
4. Why is it sometimes unnecessary to worry too much about slight white rust on galvanized coils?
Slight white rust is often a normal reaction where the zinc layer actively "sacrifices itself" to protect the steel. Zinc is chemically more reactive than steel, preferentially reacting with moisture and oxygen to protect the underlying iron substrate. Although the volume expansion of the white rust powder may make the corrosion appear severe, the actual loss of the zinc layer is often very minor. Moreover, in well-ventilated environments, the mild white rust components can further react with carbon dioxide to form a dense protective film of basic zinc carbonate, which actually helps enhance long-term corrosion resistance.
5. What is the fundamental solution to rusting caused by moisture in galvanized coils?
Long-term rust prevention hinges on prevention. The root cause of rusting in galvanized coils due to moisture is usually excessively high humidity and poor ventilation in the storage environment. Recommendations: Keep the relative humidity in the warehouse below 70%, and store goods elevated using wooden strips or wooden racks to prevent direct contact with the ground. When purchasing, choose galvanized coils that have undergone passivation treatment, as the passivation film on their surface effectively delays the formation of white rust. After delivery, implement a first-in, first-out (FIFO) system to shorten the inventory cycle. Before warehousing, check the passivation film, and ensure the packaging is intact during transportation and storage. Also note that well-passivated galvanized coils have a lower risk of white rust.