Corrosion of Aluminum-Iron Eutectic Composites

119 p.Thesis (Ph.D.)--University of Illinois at Urbana-Champaign, 1980.The corrosion of Al-Al(,3)Fe eutectic composites and individual phases, prepared by employing directional solidification or special mechanical processing to vary microstructure, was studied under conditions of preferential corrosion of the Al(,3)Fe second phase in 2.4 M H(,2)SO(,4) and preferential corrosion of the aluminum matrix by pitting in 5.0 M NaCl at pH 1.0. The "iron-like" Al(,3)Fe phase provided the total cathode reaction in both solutions and the corrosion rate depended on the metallographic parameter S(,v), the surface area of Al(,3)Fe in the volume. S(,v) is proportional to 1/L, where L is the mean intercept spacing.In sulfuric acid the continuity of the Al(,3)Fe phase was of utmost importance. In discontinuous structures the phase rapidly corroded out and the Al to Al(,3)Fe ratio increased rapidly lowering the mixed corrosion potential of the structure. For continuous structures it was found that the Al(,3)Fe phase still persisted at the bottoms of long narrow trenches formed by the corrosion of the Al(,3)Fe. For finer structures S(,v) was larger, and thus the area of Al exposed was larger leading to a faster drop in potential. The results imply that discontinuous structures would suffer less corrosion in composite systems where the reinforcing phase preferentially corrodes.In 5 M NaCl at pH 1.0 the spacing of the Al(,3)Fe was the dominant factor. Corrosion measured via hydrogen volume collection, cathode polarization, and weight loss was higher for the finer structures where S(,v) was higher. For continuous structures the area of Al(,3)Fe exposed by pitting should be proportional to pit volume while in the discontinuous structures the area would be proportional to the number of Al(,3)Fe particles in the surface of the pit since those in the volume would fall out. Equations were derived assuming random nucleation of pits and random growth of pits. The equations for the continuous eutectic structures predicted an exponential increase in the corrosion rate with time that was larger for finer structures. For the discontinuous structures predicted total pit volume increased with t('3) at longer times and was also dependent on the number of pits nucleated. The equations derived for both structures described the main features of the corrosion behavior with differences being attributable to the nonrandomness of pit nucleation and the preferential growth of pits away from Al(,3)Fe particles.Further studies of pit nucleation and growth are needed to refine the equations. Other solutions and different structures should also be studied to develop a fuller analysis of corrosion versus microstructure as a basis for alloy design.U of I OnlyRestricted to the U of I community idenfinitely during batch ingest of legacy ETD

Data for Novel Alternative Cement Binders for Highway Structures and Pavements

The contents of data file include raw data for all the data plots included in the final report titled Novel Alternative Cement Binders for Highway Structures and Pavements. The excel spreadsheets were named based on chapter numbers in the final report.The ubiquity and the necessity of concrete infrastructure prompts innovation in addressing the global challenge of meeting societal needs in the most sustainable and economical ways possible. Increasing the use of non-portland cements or “alternative cementitious materials” (ACMs) is increasingly of interest due to their special properties and to their potential to reduce the environmental footprint of concrete. The special properties of ACMs may vary by material but include rapid setting, rapid strength development, higher ultimate strength, improved dimensional stability and increased durability in aggressive environments. The increased strength and increased durability further contribute to enhanced service life which can help offset initially higher materials costs, and also to enhanced sustainability. In the past, most ACMs have primarily been used in specialty limited applications and some of them have been shown in lab-scale studies to be feasible for the partial or full replacement of traditional portland cements used in concrete. However, there is limited understanding of the scalability of construction with these material systems, their long-term performance and durability in a range of environments, and their structural response when subjected to transportation-relevant loading conditions. This data presents the results from the comprehensive investigation of the applications of these commercially available ACMs in durable and sustainable transportation infrastructure, which include the early-age and long-term material properties as well as complete multi-scale durability investigations.Office of Infrastructure Research & Development, Federal Highway Administration, 6300 Georgetown Pike, McLean, VA 22101-2296. Grant number: DRFH61-14-H-000