Corrosion inhibitors based on chitosan-heptanoate modified beidellite

Abstract

This study deals with the development of a novel inhibitor based on heptanoate anions encapsulated within chitosan-modified beidellite. Included in coating, this inhibitor ensured efficient protection of metals against wet corrosion via permanent controllable release of the heptanoate inhibitor. The interlayer Na+ ions of beidellite from Agadir basin (Morocco) were exchanged with chitosan cations. The modified beidellite was studied by diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS), thermogravimetry (TG) analysis coupled to mass spectrometry (MS) and, X-ray diffraction (XRD) analysis. The expansion of the interlayer space of beidellite by ≈1.16nm, evidenced by XRD, was consistent with the arrangement of chitosan bilayer. Exceeding positively charged sites of the biopolymer were compensated by heptanoate anions. Electrochemical impedance spectroscopy (EIS) measurements were carried out on galvanized steel immersed in a 3mass% NaCl solution. The measurements revealed improvement of corrosion inhibition by chitosan-heptanoate modified beidellite in comparison with commercially available triphosphate aluminium (TPA) anti corrosion pigments. The improved corrosion inhibition was due to the continuous leaching of hepatanoate anions as inhibitors. However, the barrier properties of coatings containing chitosan-heptanoate modified beidellite were not as high as those of TPA-based coatings, probably due to insufficient dispersion of the modified beidellite particles within the polymeric matrix.