Whole pH range anti-corrosion property of aluminium alloy coated with MFI zeolite film

Abstract

Strong protection capability of zeolite coating for AA6061 substrate from corrosion in NaCl, H 2 SO 4 and NaOH solution has been demonstrated with reduction of corrosion current by five orders of magnitude. Film resistance was identified as the governing parameter in the formation of a barrier shielding the penetration of aggressive species. For the MFI zeolite film growth on the surface of the AA6061 substrate, while the in situ crystallisation (InC) protocol generated loosely packed film made of large zeolite crystal, the dry-gel conversion (DGC) protocol prepared dense film comprising of nanoparticles. Superior protection ability of DGC-grown film is attributed to the increased film resistance associated with a dense and impermeable zeolite layer. As such, the DGCgrown film requiring thinner film thickness around 5 μm showed better anti-corrosion function than the InC-grown film.

Anticorrosion Behavior of Zeolite Coatings Obtained by In Situ Crystallization: A Critical Review

“…This activity was finalized with the creation of functional coatings for which zeolite has been used as a nano-container to enhance both the inhibiting as well as the barrier properties of the coating [34]. More recently, a dry gel conversion synthesis technique was proposed as a potentially effective approach for obtaining suitable anti-corrosion coatings [35,36]. The idea was to maintain the advantages of coating deposition obtained by sol-gel technique, combined with stability and durability observed for hydrothermal zeolite coatings.…”

“…Afterwards, other works were published evidencing the suitability of this deposition technique [8,50]. More recently, in 2018, Tsai et al [36] realized a DGC coatings by using MFI zeolite showing its performance stability in the whole pH range of NaCl electrolyte solution.…”

“…The high efficiency of DGC coating can be also related to a proper crystal morphology where zeolite nanocrystals are well packed compared to InC technique thus increasing the zeolite layer resistance [36]. More recently Tsai et al [36] compared anti-corrosion performances of MFI coatings on AA6061 alloy obtained by in situ crystallization and dry-gel conversion, respectively (Figure 5). MFI zeolite coatings showed a significant corrosion resistance in the whole pH range, evidencing corrosion current five order of magnitude lower than the uncoated Al alloy in NaCl solution.…”

“…Corrosion rate of bare and DGC coated Al 6061 substrate at varying pH in H 2 SO 4 –NaOH solutions [36]. …”

On the Anti-Corrosion Property of Dry-Gel-Conversion-Grown MFI Zeolite Coating on Aluminum Alloy

“…Zeolite film has been proven as an effective anti-corrosion coating for the protection of various metals from corrosion, particularly useful in severe corrosive environments in strong acid and base environments (pH [3][4][5][6][7][8][9][10][11][12] and in high temperature [10][11][12]. Cai and Yan summarized the exploratory works of corrosion-resistant zeolite coatings [13].…”