Why defects occur in hot-dip galvanizing
Even though hot-dip galvanizing is a well-established and standardized process, defects can occur due to incorrect design, inadequate surface preparation, or unsuitable materials. These issues may compromise the appearance, adhesion, or corrosion resistance of the zinc coating.
Understanding the root causes and adopting preventive measures is essential for engineers and designers who want to ensure the durability and functionality of galvanized components.
Common galvanizing defects and how to prevent them
- Uncoated or bare spots
- Cause: Presence of oils, paint residues, or contaminants.
- Prevention: Clean parts thoroughly and avoid surface treatments not compatible with galvanizing.
- Excessive zinc buildup or rough surfaces
- Cause: High silicon or phosphorus in steel (Sandelin effect).
- Prevention: Use steels with controlled silicon content and consult your galvanizer in advance.
- Drips and runs
- Cause: Poor drainage design or inadequate venting in hollow sections.
- Prevention: Include proper drain and vent holes; follow best practices for structural design.
- Peeling or flaking
- Cause: Incompatible materials, such as stainless steel elements or layered assemblies.
- Prevention: Avoid combining galvanizable and non-galvanizable parts in the same assembly.
- Dark stains or white rust
- Cause: Improper storage or moisture after galvanizing.
- Prevention: Store parts in dry, ventilated areas and avoid condensation.
Design tips to ensure galvanizing success
- Simplify geometries where possible to ensure uniform zinc flow.
- Avoid tight overlapping joints or crevices that may trap liquids.
- Provide access for lifting and handling during the galvanizing process.
- Use continuous welds and seal hollow sections to prevent internal corrosion.
- Consult early with the galvanizer to validate design choices and tolerances.
Zincol Lombarda: engineering support and defect prevention
At Zincol Lombarda, we don’t just galvanize—we collaborate.
With decades of experience serving clients in Milan, Lecco, Bergamo, and Como, we offer technical consulting to identify potential risks before production. Our specialists assist with:
- Drawing reviews
- Material analysis
- Galvanizing feasibility checks
- Design validation
Our goal is to help you prevent defects, save costs, and ensure that every component meets UNI EN ISO 1461 standards and your project’s expectations.
