Interesting Corrosion Inhibition Performance and Mechanism of Two Silanes Containing Multiple Phosphate Group

Abstract

Silanes and organophosphorus compounds have been widely used in the field of corrosion inhibition. Herein, two corrosion inhibitors containing multiple phosphate groups and different silane groups, namely, 1,3-bis{3-[N-(1-phosphonatediethyl)-isopropyl] aminopropyl}-1,1,3,3-tetramethyldisiloxane (BPIAT) and N,N-di-methylenephosphonate-aminopropyl dimethyl silanol (DMADS), were designed and their corrosion inhibition properties on the iron surface in 0.5 M H2SO4 solution were characterized by polarization curves and electrochemical impedance spectroscopy (EIS) at 25 °C. In order to further analyze the corrosion mechanism thoroughly, three organophosphorus compounds without silane groups, namely, Hexamethylene-diamine tetra(methylene phosphonic acid) (HDTMPA), (ethylenedinitrilo)-tetra methylene phosphonic acid (EDTMP), and diethyl 1-decylphosphonate (DDP), were also investigated. The electrochemical experimental results reveal that five corrosion inhibitors are mixed type inhibitors and the adsorption process obeys Langmuir isotherm, and the corrosion inhibition efficiency of BPIAT and DPSD is significantly higher than that of HDTMPA, EDTMP and DDP. A new corrosion inhibition mechanism was proposed by comparing the corrosion inhibition performance of five corrosion inhibitors. The corrosion inhibitors are absorbed on the iron surface by Fe-O-P covalent bonds and Van Der Waals’ force. Simultaneously, the Si-O-Si structure is conducive to the improvement of the corrosion inhibition efficiency.