Open AccessEnergy-efficient process for hot-dip batch galvanizing
Publication year - 1998
Language(s) - English
Resource type - Reports
DOI - 10.2172/594463
Subject(s) - galvanization , oak ridge national laboratory , engineering , process (computing) , coating , corrosion , mechanical engineering , process engineering , manufacturing engineering , computer science , metallurgy , materials science , layer (electronics) , composite material , physics , nuclear physics , operating system
Hot-dip galvanizing of steel sheets, pipes, and other fabrication items is a popular method of corrosion protection. Currently, steel articles are immersed in molten zinc at 860{degrees}F, thereby forming a {open_quotes}frozen{close_quotes} metal (interfacial zinc iron intermetallic layer) on the surface. Drawbacks to the current technology include the expense of heating parts at such a high temperature and the generation of by-products such as zinc alloys, zinc oxides, and smoke. Furthermore, new federal regulations have significantly reduced acceptable lead levels in coatings, because lead from galvanized, coated steel will dissolve in water. Such dissolved lead may accumulate in human bodies with deleterious results. Additionally, the use of a molten salt layer on top of zinc (top-flux) causes kettle smoke and ash evolution. Ferro Technologies, Inc. has proposed a lead-free batch technology that will significantly improve the galvanizing process. The new Thermo Prep{trademark} process protects steel surfaces with a thermally stable flux by preheating parts to 400{degrees}F to 450{degrees}F in a separate furnace, and then immersing them in molten, lead-free zinc for a short period of time. The use of a thermally stable pre-flux would eliminate the need for top-flux, thereby reducing associated wastes