Synthesis and characterization of atmospheric pressure chemically vapor deposited aluminum

This study investigates the use of atmospheric pressure chemical vapor deposition (APCVD) to produce high quality aluminum coatings for corrosion protection of steel. The coatings were produced through thermal decomposition of tri-isobutyl-aluminum (TIBAL) over the 275 to 300°C temperature range. Under optimal deposition conditions, growth rates as high as 1.2 mum/min were achieved. X-ray photoelectron spectroscopy, auger electron spectroscopy, glow discharge optical emission spectroscopy and nuclear reaction analysis revealed that the coatings consisted essentially of pure aluminum (∼99 at.%) with oxygen and carbon present as minor constituents. The coatings were characterized in terms of their morphological, structural, electrical, and mechanical properties, and corrosion performance. The coatings were found to be continuous with a rough surface topography typical of CVD metal deposits. The Al coatings showed x-ray diffraction patterns that were similar to the typical polycrystalline aluminum powder pattern regardless of deposition conditions. Cross-sectional SEM micrographs confirmed that the APCVD process can offer excellent step coverage and throwing power. Corrosion testing revealed that APCVD Al coatings exhibit excellent corrosion resistance. With such correlations, this study offers an environmentally benign alternative to cadmium plating, as well as promises to provide high production throughput, low cost, and coatings with desirable properties and performance.