Narrow gaps in overlapping structural steel surfaces are problematic when being hot-dip galvanized due to the potential for trapped cleaning solutions between the surfaces. A seal-weld is often used to prevent the cleaning solutions from penetrating this gap. However, these welds are not necessary used for strength, and add fabrication costs because of the additional weld. The purpose of this research is to provide alternatives, which fall under two major categories, to the seal-weld fabrication process. The first one was motivated by the steel fabrication industry and uses a commercial silicone caulk to seal the narrow gap instead of a seal-weld. The second was motivated by the galvanizing industry and increases the narrow gap to a minimum of 3/32 in. to allow free flowing of the liquids including viscous molten zinc. 45 specimens in six different overlapping configurations were tested. Three experimental tasks were performed as part of this research: two different types of silicone caulks were used to partially substitute the seal-weld to prevent fluid penetration; an accelerated corrosion test was performed to determine the long-term corrosion resistance of each configuration; and a coating layer evaluation was performed to investigate the bond of the metallurgical layer between the steel and the coating. Results indicate that silicone only partially prevented the penetration of the cleaning solutions into the gap but performed poorly when fully galvanized. Also, the accelerated corrosion and coating investigations indicated that the suggested caulks and the 3/32 in. gap were not as efficient as the seal-weld solution. / Master of Science / Hot-dip galvanizing is a corrosion protective process for steel. The process involves dipping the base material into a series of different baths. The first set of baths are the cleaning baths and the last bath is the zinc coating bath. In the cleaning baths, certain chemicals are applied to clean the steel surface from oxides and rusts and to prepare the steel for a better zinc coating. When steel members that are fabricated with narrow gaps between overlapping surfaces are subjected to the galvanizing process, the quality of the zinc coating is often inferior along the interface between the two surfaces. This problem occurs because the cleaning solutions—which have a lower viscosity than zinc—get trapped inside the gap while the molten zinc cannot galvanize narrow gaps due to its high viscosity. For this reason, overlapping steel members are seal-welded to prevent such issues. Since seal-welding is not efficient from a fabrication standpoint, the purpose of this research is to provide alternative geometrical overlapping surface configurations. These configurations were subjected to the galvanizing process. To evaluate their performance, three separate tasks were applied through this investigation. The first task involved sealing the gap with commercial silicone sealants instead of a seal-weld, the second task was an accelerated corrosion test, and finally a bond investigation of the coating of the overlapping surfaces was performed. Results have shown that the proposed alternatives did not provide an improved detail for overlapping steel surfaces compared to the existing seal-weld.
| Identifer | oai:union.ndltd.org:VTETD/oai:vtechworks.lib.vt.edu:10919/83182 |
| Date | 07 May 2018 |
| Creators | Sultan, Abdullah Emad |
| Contributors | Civil and Environmental Engineering, Hebdon, Matthew H., Roberts-Wollmann, Carin L., Mokarem, David W. |
| Publisher | Virginia Tech |
| Source Sets | Virginia Tech Theses and Dissertation |
| Detected Language | English |
| Type | Thesis |
| Format | ETD, application/pdf |
| Rights | In Copyright, http://rightsstatements.org/vocab/InC/1.0/ |
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