| Development of corrosion resistant materials to molten zinc attack for applications in galvanizing pots has long been desired, because better corrosion resistance could lead to a longer production campaign. The research objectives of this project were to develop new bulk materials and surface treatments/coatings for life improvement of molten metal bath hardware (bearings, sink roll, stabilizing rolls, corrector rolls, and also support roll arms and snout tip) in continuous hot-dip process used for coated steel strip.; The ultimate goal of the project is to increase the molten Zn bath components life by an order of magnitude which results in large energy saving (estimated at 2 trillion BTU/year). Estimated cost saving would be approximately {dollar}46 million/year for the 57 lines operating in the United States of America.; Extensive experimental studies were conducted on over 60 different samples of various materials (monolithic alloys with and without treatment, weld overlays, and ceramics) in molten Zn-0.16Al at 465°C. Test durations were 1h to over 9000h in the static condition, over 50h in the dynamic condition, and up to 24h in the wear condition. Data were recorded as weight change per unit area as a function of time and temperature. The reaction products were analyzed for phase composition and their distribution using SEM, EDS, XRD, and optical microscope. Corrosion rates for each selected alloys were calculated. The SS Type 316L results were used as a baseline. Comparisons between the corrosion behaviors of the stainless steel type 316L and the selected materials were made.; Based on our static, dynamic, and wear immersion experimental data a mechanism for alloy corrosion in molten zinc was proposed. Alloys containing Fe, Cr, and Al as its major components results in the formation of (Fe, Cr, Al)XZnY intermetallic phases and oxides at the alloy/zinc interface when exposed to molten zinc in air. Most of the alloys studied in present investigation, corrosion resistance improved due to the formation of intermetallic phases and oxides at the alloy/zinc interface.; The following alloys, Metaullics alloys 2012 and 2020, Tribaloy 800, ACD (Vesuvius ceramic), W-20Mo Weld Overlay, and ORNL alloy 4-2 (pre-oxidized condition), were chosen to undergo in plant testing based on our results. These alloys have met the acceptance criteria of ten time's lower corrosion rate than currently used SS Type 316L. |
