Progressive Dip Galvanizing: What It Is and When to Use It
In this article:
Hot-dip galvanizing is the ideal choice for corrosion protection. It coats the steel with a layer of zinc. This “sacrificial zinc” in turn protects it from rust. In many cases, galvanized steel can even outlast the project itself.
But what if you have a complicated item to galvanize? What if it is too large to fit into the kettle, or if it has an irregular geometry that hinders full immersion in the molten zinc?
In cases like this, progressive dip galvanizing is the solution. In this article, we’ll examine what progressive dip galvanizing is, its many advantages and when you should consider it.
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What Is Progressive Dip Galvanizing?
In standard hot-dip galvanizing, a steel component is fully immersed in molten zinc to form a protective coating.
By contrast, progressive dip galvanizing is used when a component is too large or irregular to be fully covered by a single dip in a galvanizing kettle. Therefore, the component is galvanized in stages by immersing sections of the steel.
When Is Progressive Dipping Necessary?
Sometimes, an item is limited due to the size of the galvanizing kettle. If the component exceeds the dimensions of the kettle, it requires progressive dipping.
Other instances when progressive dip galvanizing is necessary include:
- Items that are unusually long or too tall to fit into a kettle
- Items that have irregular geometry that make full immersion difficult
- Components that have offsets or projections
- Complex fabrications
- Structures that require intensive thermal management during the process
Does Progressive Dipping Affect the Overall Coating Quality?
Some may be concerned that progressive dipping compromises the corrosion protection of galvanization. However, in actuality, the coating thickness meets all the same requirements as regular hot-dip galvanizing.
The only real difference is that there may be some faint transition lines on the component where the molten bath overlapped. This is purely a cosmetic difference that will gradually fade. It has no influence on the integrity of the corrosion resistance.
In addition, progressive dip galvanizing is still required to meet all applicable ASTM and industry standards. The inspection criteria are also the same.
Progressive dipping is recognized as compliant when proper procedures are followed.
Are There Any Drawbacks of Progressive Dip Galvanizing?
When you need to galvanize large pieces, progressive dip galvanizing is the ideal choice. However, there are a few drawbacks.
- Transition lines: We mentioned this earlier. While these do not affect the strength of the corrosion-resistant coating, for projects that require detailed aesthetics, progressive dipping may not be the best option.
- Increased time: Because the process requires multiple dips, it can take longer than regular single-dip galvanizing.
- Cost: Progressive dipping may be more expensive depending upon the shape and size of the component.
If you believe your project is a candidate for progressive dipping, we’ll be happy to meet with you to not only learn more about your venture, but to help you find the best solution that provides both efficiency and reliable corrosion resistance.
5 Factors to Consider with Progressive Dip Galvanizing
At South Atlantic, we always utilize the best practices when dipping progressively. The factors we consider include:
- Utilizing proper vent holes
- Avoiding unnecessary complexity if possible
- Considering material thickness
- Planning overlap zones in less visible areas
- Communicating regularly with our customers throughout the process
Whether You Need Progressive or Typical Galvanizing, We’ve Got You Covered
For more than 50 years, we have served large, national brands, earning trust and loyalty through our dedication to quality and stellar customer service.
We invite you to contact us for a no-hassle quote to see the many ways we have you covered.
Key Takeaways
- Hot-dip galvanizing provides long-lasting corrosion protection by coating steel with sacrificial zinc that protects against rust.
- Progressive dip galvanizing is used when steel components are too large or irregular to be fully immersed in a galvanizing kettle at one time.
- This method galvanizes oversized or complex components in stages without sacrificing corrosion resistance.
- Progressive dipping is commonly required for long, tall, offset, or complex fabrications that exceed kettle dimensions.
- Coating thickness and corrosion performance from progressive dip galvanizing meet the same ASTM standards as standard hot-dip galvanizing.
- Any visible transition lines from overlapping dips are cosmetic only and do not affect durability or protection.
- Progressive dip galvanizing may involve longer processing times and higher costs compared to single-dip galvanizing.
- Proper design considerations, such as venting, material thickness, and overlap planning, help ensure optimal results.
- Working with an experienced galvanizer ensures quality control, compliance, and reliable project outcomes.
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Sources:
American Galvanizers Association, “The Progressive Dip Process,” https://galvanizeit.org/knowledgebase/article/the-progressive-dip-process
“Considerations for Progressive Dipping,” https://galvanizeit.org/knowledgebase/article/considerations-for-progressive-dipping
