It is important to properly vent overlapping and contacting surfaces to prevent trapped moisture (from pickling or flux solution used in the galvanizing process) or gas from flashing to stream, which may result in localized uncoated surfaces. Additionally, pressure increases resulting from trapped moisture flashing to steam could possibly rupture the fabrication.
It is important to consult with your galvanizer before fabricating any piece that will include overlapping surfaces. The galvanizers experience may greatly assist in deciding between a completely seal-welded joint and a skip-welded joint.
Cleaning solutions used in the galvanizing process can become trapped between overlapping and contacting surfaces. Upon immersion into the galvanizing bath at temperatures of more than 800 F (430 C), this moisture is converted to superheated steam that can create internal pressures greater than 3600 psi (25 MPa). There are prescribed methods of welding and consideration of total overlapped area that should be understood in the design process.
© 2020 American Galvanizers Association. The material provided herein has been developed to provide accurate and authoritative information about after-fabrication hot-dip galvanized steel. This material provides general information only and is not intended as a substitute for competent professional examination and verification as to suitability and applicability. The information provided herein is not intended as a representation or warranty on the part of the AGA. Anyone making use of this information assumes all liability arising from such use.