Synthesis of polyesteramides: poly(ethylene adipate amide) and poly(ethylene succinate amide) and their application as corrosion inhibitors in paint formulations

Aliphatic polyesters based on adipic or succinic acid were synthesized by polycondensation reaction to produce poly(ethylene adipate) (PEA) and poly(ethylene succinate) (PES), respectively. The prepared polyesters (PEA and PES) were modified with monoethanol amine to produce polyesteramides, namely polyethylene adipate amide (PEAA) and polyethylene succinate amide (PESA). Full characterization of PEA, PES, PEAA and PESA was achieved using thermal, spectroscopic, and gel permeation chromatography analyses. The prepared aliphatic polyesters (PEA and PES) and polyesteramides (PEAA and PESA) were evaluated as corrosion inhibitors in paint formulations. Two groups of paints were prepared with 24 paint formulations based on medium oil alkyd resin, talc, titanium dioxide, drier and the prepared polymers with different types and concentrations. All the formulations are free from any inorganic anticorrosive pigments. PEA and PEAA were incorporated in Group I formulations. Paint formulations that contain PEA are six formulations F1A, F2A, F3A, F4A, F5A and F6A in addition to F1Aa, F2Aa, F3Aa, F4Aa, F5Aa and F6Aa based on PEAA with different concentrations 0.5%, 1.5%, 2.5%, 3.5%,4.5% and 5.5%, respectively. Group II formulations contain twelve other prepared formulations F1S, F2S, F3S, F4S, F5S and F6S based on PES, in addition to F1Sa, F2Sa, F3Sa, F4Sa, F5Sa and F6Sa based on PESA with the same series of concentrations. Physical, mechanical, and chemical properties of the coated films were determined. Corrosion tests in addition to surface analysis by a scanning electron microscope were performed to study the protection efficiency of such coats on steel. It was found that the synthesized polyesteramides can protect steel from corrosion successfully in 3.5% NaCl solution depending on their adsorption on the steel surface. The extent of steel protection coated with PESA formulations was slightly higher than PEAA.