Among the various surface modification processes, the hot-dip aluminizing process has increasingly evoked considerable attention. This method has proved to be commercially cost-effective and technically better than galvanizing. In contrast to hot-dip aluminized steel components, galvanized components cannot be used in service conditions at elevated temperatures. During the last few years, intensive research by researchers has yielded new insights into metallurgical aspects of aluminized coating in as-dipped and annealed condition. The present review gives a bird’s eye view of the hot-dip aluminizing process, from the early years of its inception to the current research on aspects of the aluminized coating. The progress of research on thermodynamic studies, phase equilibria, phase identification, and their crystallographic features have been traced in this attempt. This review is not restricted to briefing the research performed so far but also points out several issues of discrepancies among the results of the published literature. Special emphasis has been given to the phase development in the coating during annealing and the increasing horizon of application of hot-dip aluminizing to alloy steels in hot stamped conditions. Reference has also been made to state-of-the-art topics embracing the current research on computer simulation software and sophisticated experimental techniques. However, lower surface hardness and economy restrict the wide application of the hot-dipping process.

This study examines the influence of cenosphere particle size and sintering parameters on the microstructure and electrochemical behavior of Ti-cenosphere composite foam fabricated by powder metallurgy route. Cenosphere has been added as a space holder material to develop Ti composite foam because of its abundant availability and low cost. Ti (particle size between 250 μm and 350 μm) and cenosphere (with a varying particle size of < 150 μm, 150 μm-200 μm and > 200 μm) in the ratio of 75 : 25 (wt %) were compacted using 100 MPa of applied pressure and sintering temperatures of 1000 and 1200 °C with sintering time ranging from 2 to 6 h at a heating rate of 25 °C/ min. A defect-free microstructure with the uniform dispersion of cenosphere particles in the Ti matrix was observed with the cenosphere particles in the size range of 150-212 μm at a sintering temperature of 1000 °C for 4 h. The porosity content in the syntactic foam varied from 34 to 50 % and decreased with increasing sintering time and temperature. Based on a detailed study of corrosion behavior in Hank's solution, the composite foam with cenosphere particles in the size range of 150-212 μm and sintered at 1000 °C for 4 h showed the highest corrosion resistance.

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