Q: Can galvanized coils resist mold growth or corrosion?
A: The pure zinc coating on galvanized coils is not a bactericide and does not actively inhibit mold spore germination. However, its dense metal surface offers less support and nutrition for microorganisms compared to ordinary steel.
However, if the galvanized layer has defects, such as an incomplete passivation film or residual organic matter, mold can find a foothold and grow on dust or dirt on the surface of the galvanized coil in a humid environment.
2. How exactly does mold corrode galvanized coils?
A: Mold doesn't "eat" the metal, but during its metabolism, it secretes organic acids such as citric acid and oxalic acid. These acidic metabolic products damage and dissolve the protective passivation film on the zinc surface, thus initiating the corrosion process.
Furthermore, when mold grows on the surface, the area covered by its mycelium and the exposed area form a microscopic "oxygen concentration cell." This electrochemical difference further accelerates localized pitting or perforation.
3. Do all molds have the same effect on galvanized coils? Which mold has the greatest impact?
A: Different mold species have significantly different effects on galvanized coils. Studies have shown that *Aspergillus niger* has a significant accelerating effect on zinc corrosion, significantly damaging and thinning the galvanized layer.
Research has confirmed that in control experiments, galvanized steel sheets exposed to a high concentration of mold for 30 consecutive days developed numerous tiny corrosion spots on the surface, and the coating thickness decreased sharply from 8 micrometers to 6 micrometers.
4. Besides corrosion, what other practical effects does mold have on galvanized coils?
A: When mold forms a biofilm on the surface of galvanized coils, it triggers a series of chain reactions. First, the mycelium traps moisture and dirt for a long time, significantly reducing the material's self-cleaning ability, which may lead to discoloration, powdering, or decreased adhesion of the galvanized sheet surface.
More importantly, long-term microbial erosion will greatly shorten the overall service life of the galvanized layer. Studies show that after mold corrosion, the corrosion resistance life of galvanized sheets in subsequent salt spray tests will be shortened by about 50%. In industries with extremely high cleanliness requirements, such as pharmaceuticals and food processing, this poses a significant risk of cross-contamination.
5. How to effectively improve the resistance of galvanized coils to mold and corrosion?
A: The simplest and most effective method is to ensure the surface of the galvanized coil is clean and dry, and to store it in a well-ventilated environment, avoiding prolonged exposure to high humidity (85%-95%).
For high-risk applications, advanced protection is recommended. For example, choosing galvanized products with a specific organic and inorganic composite "anti-mold passivation film," or applying a dense plastic coating (such as powder coating) to the surface, can effectively block direct contact between mold and the zinc layer. Furthermore, applying novel superhydrophobic and antifouling coatings can simultaneously achieve the dual functions of corrosion resistance and resistance to pathogenic fungal adhesion.