Synthesis and Corrosion Resistance of High-Silica Zeolite MTW, BEA, and MFI Coatings on Steel and Aluminum

High-silica zeolite with (MTW), Beta with (BEA), and ZSM-5 with (MFI) coatings were synthesized by hydrothermal crystallization without seeding using a new two-silica method on Al-alloy (Al-2024-T3 and Al-6061-T4) and stainless steel (SS-304). The pure-silica MTW and BEA coatings synthesized in this study have not been previously reported. All coatings are continuous and have excellent adhesion. The as-synthesized zeolite coatings were tested by a dc polarization technique and found to be highly corrosion resistant in severely corrosive acidic (0.5 M aqueous solution) and alkaline (0.1 M NaOH aqueous solution) media. In particular, a pure-silica MFI coating of only a few hundreds of nanometers thickness was formed within a relatively short crystallization time (e.g., 15 min), and was shown to provide sufficient protection against corrosion.