Evaluation of Corrosion Inhibition Performance of Two Novel Multifunctional Silane Containing Phosphonyl Groups Synthesized by Convenient Mannich Reaction

Abstract

AbstractTwo novel iron corrosion inhibitors were prepared via convenient Mannich reaction which named N,N’‐dimethylene phosphonyl aminopropyl dimethyl silanol (DPDS) and N,N’‐dimethylene phosphonyl aminopropyl methyl silandiol (DPMS). To analyze the relations between the corrosion inhibition properties and the configuration of the moleculars, N,N’‐dimethylene phosphonyl propylamine (DPPA) was also selected to be compared with these two silanes. These three compounds have same amount of phosphonyl groups in one molecular while they have different amount of hydrolysis groups. Their corrosion inhibition properties of the iron were investigated in sulfuric acid solutions by using electrochemical methods. Electrochemical results have shown that the corrosion inhibition efficiency of these three inhibitors for the iron increased firstly and then decreased when the concentration reaching the maximum value. The absorption behaviors of these three inhibitors on the iron surface fitted well with the Langmuir isotherm model. Based on the calculation of standard Gibbs free energy and equilibrium constant, the absorption processes were determined to be chemisorption. What's more, DPMS showed the better corrosion inhibition properties than DPDS and DPPA. A hypothesis of arrangement of these three inhibitors on the iron's surface was put forward to explain the difference among these three inhibitors.