Date of Graduation

2008

Document Type

Thesis

Abstract

Steel sheet manufacturers across the globe, face a huge loss of production due to the molten metal corrosion of the pot hardware in continuous galvanizing lines. The development of steel sheet with corrosion resistant for more than 30 years using a high aluminum content zinc coating has made an impact in the construction industry. High aluminum content bath (55 wt%) causes severe corrosion of the pot hardware and causes huge repair and replacement cost with frequent stoppages. One of the main reasons for stoppages is the severe dross formation over the submerged hardware (sink roll), which results in poor coating layer over the steel sheet. Complete understanding of the mechanism of the dross formation over the submerged hardware has not yet been completely achieved. In order to establish the dross formation mechanism, an array of tests was performed. Initial inhibition of Al attack by the silicon rich layer and further formation of Fe2Al 5 layer hindering the diffusion of the Al into the substrate were observed. Also, the effect of the hydrodynamic motion of the bathe in the dross formation mechanism was established. A series of tests for efficient removal of the dross formed over the sink roll using high hardness, corrosion resistant materials were conducted at 600°C. After these tests, an efficient scraping process with a potential for energy and cost savings was developed with a better scraper material, resulting in a reduction of 75% in line stoppages.

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