Hot dipped galvanizing
Hot dipped galvanizing
(OP)
I had a steel fabricator today tell me that a cold-formed tube section needs to have a "blow hole" provided before it can be hot-dippped galvanized, otherwise the built up air pressure may cause a fully sealed section to rupture. Is this correct, or was the fabricator leading me on?






RE: Hot dipped galvanizing
RE: Hot dipped galvanizing
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RE: Hot dipped galvanizing
Also good to provide a drain to keep ice from busting the tubing is outside.
Dik
RE: Hot dipped galvanizing
It also helps if the items don't float!
RE: Hot dipped galvanizing
RE: Hot dipped galvanizing
What increase in mass can I expect with a hot dipped galvanized finish and what additional wall thickness will result?
RE: Hot dipped galvanizing
RE: Hot dipped galvanizing
Zinc density is 7,140 kg/m^3.
RE: Hot dipped galvanizing
The thickness of galvanizing varies with the thickness of the steel. The 600 g/m2 noted by apsix would be typical for steel about 6 mm thick, but the zinc deposition increases with steel thickness. It can easily be 1000 g/m2 for rolled sections. And with a tube, you have both outside and inside zinc. Suggest you review information published by Industrial Galvanizers, or call a local galvanizer for advice.
RE: Hot dipped galvanizing
RE: Hot dipped galvanizing
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RE: Hot dipped galvanizing
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"In the hot-dip galvanizing process, steel is completely coated with corrosion-inhibiting zinc, which forms a highly abrasion-resistant metallurgical bond with the base steel. In order to ensure that all interior and exterior surfaces are protected from corrosion, entire steel fabrications are lowered into and raised out of cleaning solutions, flux solutions, and molten zinc metal. In order to facilitate interior and exterior cleaning and coating, it is necessary to provide holes in fabrications to be galvanized.
The primary reason for vent and drain holes is to allow air to be evacuated from within and around the fabrication, allowing it to be completely immersed in the cleaning solutions and molten zinc and for the excess zinc and solutions to drain out and away from the part.
The secondary reason is that if fabrications to be galvanized are not properly vented, cleaning solutions or rinse waters trapped in overlapping or contacting surfaces flash to steam. The resulting pressure increase (up to 3600 psi [25MPa]) can rupture the fabrication. Additionally, trapped moisture that flashes to steam can result in localized uncoated surfaces.
Because items being galvanized are immersed in and withdrawn from all cleaning solutions and molten zinc at an angle, vent holes should be located at the highest point and drain holes at the lowest point as mounted during the galvanizing process."
RE: Hot dipped galvanizing
RE: Hot dipped galvanizing