Preparation And Inhibition Property Of Amino Acid Intercalated Layered Double Hydroxides

Layered Double Hydroxides (LDHs) are very important inorganic functional materials with high temperature resistance, radiation resistance and good anti-aging performance and they have an extremely good prospect in the preparation of environment-friendly inhibition film materials. Currently, the research of the application of LDHs films in metal corrosion and protection is still in initial stage.In this study, amino acids, the environment-friendly corrosion inhibitor, were intercalated into LDHs by taking the advantage of the special structure of LDHs to prepare the hybrid materials with superior properties of both LDHs and inhibitors. They overcome the shortcoming of complexity, environmental pollution and high cost in common method of corrosion protection. This method has important scientific significance and practical value.Firstly, the environment-friendly corrosion inhibitors, L-glutamic acid, L-aspartic acid and L-tryptophan, were intercalated into Zn-Al-LDHs by coprecipitation at alkaline condition. The structure of nanohybirds were characterized by PXRD and FT-IR. The PXRD patterns indicated that the basal spacing of the nanohybirds was obviously larger than pristine LDHs and 003 peak was shifted to the low 2θvalue, which indicated that the nanohybirds were formed by the intercalation of the amino acids into the Zn-Al-LDHs. The successful synthesis of the nanohybirds were also proved by the FT-IR spectra, which indicated the existence of characteristic groups of amino acids.The nanohybirds were deposited on copper surface by colloid deposition method and the surface morphology was analyzed by scanning electron microscopy(SEM). The results showed that the amino acid-LDHs hybrid materials can form very impact and uniform films on copper surface. The quality and protection performance against corrosion to copper of hybrid films in the NaCl solution were characterized by electrochemical impedance spectroscopy (EIS) and polarization curves. The results showed that hybrid films have high surface coverage and inhibition efficiency.Finally, the anticorrosion mechanism of amino acid-LDHs hybrid films was studied preliminary by immersion test. The result of SEM showed that the surface morphology of hybrid films changed significantly after the hybrid films were immersed in NaCl solution 24 h. The amino acid-LDHs sheets were not packed densely because of the penetration of NaCl solution into the internal films. The results of PXRD and EDS indicated that Cl- was intercalated into LDHs. It was revealed that NaCl solution penetrated into hybrid films and ion exchange reaction took place in the immersion process. The conclusions are as follows: on the one hand, the reducing of Cl - in the solution can slow down the corrosion of substrate. On the other hand, the release of amino acids from LDHs to solution also prevented the corrosion reaction. So the inhibition efficiency of amino acid-LDHs hybrids was improved.