1.What are the core issues in raw materials and pretreatment?
Inadequate strip surface cleanliness. Symptoms: Residual oil, scale, iron powder, or rolling fluid on the strip surface can cause zinc coating failure (zinc coating failure), blistering (oil volatilization and formation of bubbles), or pinholes during galvanizing.
Poor strip shape
Problem manifestations: The strip exhibits wavy, cambered, and cambered shapes, resulting in uneven contact between the strip and the zinc solution during galvanizing. This can lead to large variations in coating thickness (too thick at the edges or too thin in the center), and can even cause equipment jamming and strip breakage.
2.What are the core technical issues of the galvanizing process?
Hot-dip galvanizing forms a coating by immersing the strip into molten zinc liquid (450-460℃). The core contradiction is the matching of the zinc liquid composition, temperature and strip state.
3.What are the core issues of the electrogalvanizing process?
Poor Coating Uniformity and Pinholes
Symptoms: Uneven thickness (thick at the edges, thin in the middle) or pinholes (tiny holes) appear on the strip surface, affecting appearance and corrosion resistance.
Insufficient Coating Adhesion
Problem symptoms: Coating peeling ("peeling") during bending or stamping, incomplete pretreatment (residual oxide film), or hydrogen embrittlement during electrolysis (hydrogen ions penetrate the strip, causing separation of the coating from the substrate).
4.What are the core issues in the post-processing stage?
Passivation Film Failure
Problem manifestations: Passivation films (such as chromate passivation and chromium-free passivation) have poor adhesion (easily peeling) and insufficient corrosion resistance (premature white rust appears during salt spray testing).
Uneven oil application or contamination
Problem symptoms: Rust-proof oil (such as hard film oil or volatile oil) is applied too thickly (causing slippage during subsequent processing) or too thinly (inadequate localized rust protection), or impurities (such as iron powder) are mixed in, causing surface contamination.
5.What is the core issue of production efficiency and cost control?
Balancing Speed and Quality: Increasing strip speed can increase production capacity, but this can also lead to: insufficient pretreatment time (incomplete degreasing/pickling); uneven cooling of the galvanized layer ("zinc flow marks"); and insufficient curing of the post-treatment film.
Solution: Upgrade equipment to meet the process requirements of higher speeds.
Zinc Consumption and Waste Control
Excessive zinc consumption directly increases costs, primarily due to: excessively thick coatings; excessive zinc pot slag (excessive iron content in the zinc bath, resulting in Fe-Zn slag, resulting in 3-5 tons of zinc loss per week during slag removal); and strip breakage leading to zinc bath waste.
Key Control Points: Optimize air knife parameters to reduce excess coating; reduce zinc slag through online zinc bath composition analysis; and improve equipment stability to reduce strip breakage.