Abstract
Layered double hydroxides (LDHs) intercalated with corrosion inhibitive species are considered as promising additives to protection coatings. However, the conventional method of LDH preparation via co-precipitation followed by anion exchange is a water consuming and slow process hardly applicable to industrial use.In this work, a novel approach to LDH synthesis via hydration of sol-gel prepared mixed metal oxides and two-step anion exchange, all assisted by high-power sonication, was applied. MgAl and Mg-Al-Ce LDH with cations ratios 2:1 and 2:0.9:0.1, respectively, intercalated with corrosion inhibitive dihydrogen phosphate anion were successfully prepared.The obtained LDH were characterized by X-ray diffraction and scanning transmission electron microscopy. Anion release from these LDH in NaCl solutions and their corrosion inhibitive action on cast iron samples were monitored by electrochemical impedance spectroscopy. The results show that the dihydrogen-phosphate-intercalated LDHs produced using the novel technique are efficient in corrosion protection.
Highlights
A wide variety of protective coatings from one-layer coatings to complex combinations are used nowadays on metallic structures owing to the easy application and cost efficiency.[1]
We report on the layered double hydroxides of the [Mg1-xAlx(OH)2]x+(Ay)x/y·zH2O system (hereafter Mg(n)Al-A, where n=(1-x)/x is the Mg/Al molar ratio) prepared using a novel approach
High-power sonication assisted synthesis and anion-exchange were successfully applied to produce Layered double hydroxides (LDHs) intercalated with dihydrogen phosphate (H2PO4-), demonstrating this novel approach as an efficient alternative to the conventional co-precipitation synthesis technique
Summary
A wide variety of protective coatings from one-layer coatings to complex combinations are used nowadays on metallic structures owing to the easy application and cost efficiency.[1] Coating performance is dependent on intrinsic properties of the film (barrier properties), substrate/coating interface and the inhibitive pigments used to prevent corrosion in aggressive environments. A number of organic and inorganic species intercalated into layered structures has been proposed and optimized for application in protective coatings [1]. Layered double hydroxides (LDHs) are composed of positively-charged mixed metal MII-MIII hydroxide layers with charge-compensating anions Ay- and water molecules intercalated between layers [3]. Parameters x and z can vary over wide ranges thereby enabling flexibility of the LDH structure and allowing intercalation of anions with different sizes and charges [3,4,5,6]
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