Abstract
MFI zeolite film coated on AA6061 alloy was prepared from fumed silica modified with/without n-octyldecyltrimethoxysilane (ODS) by means of dry gel conversion (DGC) method. The DGC-grown MFI zeolite film could form a strong barrier to protect AA6061 surface against the corrosion from NaCl solution. By using fumed silica as a starting material, the hydrophilicity and anti-corrosion capability of the MFI zeolite film declined with increasing humidity in the DGC synthesis. By silanization with ODS, the surface hydrophobicity of the MFI zeolite film increased, leading to substantial enhancement in anti-corrosion capability. On the other hand, MFI film grown from ODS-modified fumed silica exhibited low hydrophilicity and a much improved anti-corrosion protection property by four orders of magnitude, even stronger than the ODS post-treated MFI film. The strong anti-corrosion capability is attributed to the “thick layer” surface hydrophobicity of zeolite crystal.
Highlights
Hexavalent chromium Cr(VI) has been proven as robust and endurable protection coating of metal to prevent from the attacks by destructively aggressive environmental components such as acid, base and chloride
We have demonstrated that dry gel conversion (DGC) process is a versatile and effective process for preparing zeolite coating with high surface coverage on metal surface for anti-corrosion protection
MFI zeolite film coated AA6061 surface was prepared by dry gel conversion (DGC) method
Summary
Hexavalent chromium Cr(VI) has been proven as robust and endurable protection coating of metal to prevent from the attacks by destructively aggressive environmental components such as acid, base and chloride. Cr(VI) has been widely used in the pre-treatment and primer layers of metal. RoHS (Restriction of Hazardous Substances) has regulated the application of Cr(VI) coating. Trivalent chromium pre-treatment is used as the main substitution of. Non-chromate coating is the most environmentally-friendly and desirable alternative, only very few Cr-free coatings have been proven as a practical solution [1]. Strong metal protection could be provided by corrosion inhibitors, physical barriers, and galvanized substances
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