253 Mat.-wiss. u. Werkstofftech. 2012, 43, No. 3 DOI 10.1002/mawe.201200824 Development of corrosion protective polymeric coatings from a non-edible seed oil Entwicklung einer Polymerbeschichtung zum Schutz vor Korrosion gegen Bioöl M. Alam 1 , M. R. Shaik 2 , N. M. Alandis 2 In this study, we have developed corrosion protective coatings material from Pongamia glabra seed oil. First, oil was converted to pongamia oil epoxy (POE). The resin was synthesized by the reaction of POE with phthalic acid to develop polyester (PE) and further treated with diethylene triamine (DTA) in different (20–35%wt) amount. The structural elucidation of POE and PE were carried out by FT-IR, 1 H-NMR and 13 C-NMR spectroscopic techniques. Thermal behavior of PE-30 was studied by thermogravimetric analyses (TGA) and differential scanning calorimetry (DSC). The coatings of PE-DTA resins were prepared on mild steel strips to investigate their physico- mechanical and corrosion performance. Corrosion protection of coated panels were examined in different corrosive media (3.5 wt% HCl, 3.5 wt% NaOH, 5.0 wt% NaCl) using potentiody- namic polarization and AC impedance. Thermal analyses revealed that PE-30 may find applica- tion as eco-friendly corrosion protective coating safely used up to 175 8C. Keywords: pongamia glabra / Precipitates / oil epoxy / coatings / Schlüsselwörter: Pongamia fladbra / Ablagerung / Edpoxidöl / Beschichtungen / 1 Introduction Polymeric materials derived from renewable natural resources have been enjoying a continuous growing interest in the past decade from the academic and industrial point of view. The advantages of these polymers are eco-friendliness, easy availabil- ity and possible biodegradability [1–4]. The development of use- ful biodegradable polymeric materials has encouraged scientists to use readily available renewable raw materials like carbohy- drates, lignin, starch, gums, chitosan and seed oils. Out of these, seed oils like soyabean, linseed, castor, safflower, coconut, arge- mone, olive are the major renewable resources [5–10]. Research and development efforts are being focused on the use of non- conventional seed oils in the field of polymer coatings. Pongamia glabra (karanja) belongs to the family Legumina- ceae. It is medium sized tree with a short crooked trunk and broad crown of spreading or drooping branches. It is considered to be a native of Western Ghats in India and occurs naturally in most parts of the Indian subcontinent [11]. It can grow under a wide range of agroclimatic conditions and is a common sight around coastal areas, riverbanks, tidal forests and roadsides [12]. The tree is valued for shade, ornamental purpose, seed oil, fodder and green manure [11]. The oil content 28–32% having good amount of unsaturation with a higher concentration of oleic acid. Pongamia seed oil (PO) is reportedly used in bio-diesel as well as in surface coatings [12–14]. In the field of surface coat- ings, many seed oils are used through a different route to develop various polymers like alkyd, polyepoxy, polyesteramide, polye- theramide, polyesters and others [5, 6, 15, 16]. Phthalic acid is generally used in the area of polymers for the preparation of polyesters, polyesteramides, polyurethanes and others [7, 9]. Aliphatic/aromatic amines such as diethylene tri amine (DTA) is used as a curing agent for different types of poly- mers like epoxy, polyester, polyesteramide [7, 17–24]. It contains three amine groups in one molecule-two primary amines at the end of ethyl group and one secondary amine in between two ethyl chains. Therefore, we expect this amine as a useful good curing agent for a oil based polyester system. In this article, we have reported the epoxidation of pongamia glabra seed oil through per acetic acid in situ reaction [7, 25, 26]. Epoxidised PO (POE) is further treated with PA to form polyester (PE); the latter is further cured with DTA and used as coating material for mild steel. A voluminous literature reports that acid/ anhydride and amine curing agent are used for commercial epoxy resins like diglycidyl ether of bisphenol A (DGEBA) [27]. Physico-chemical characterizations such as refractive index, spe- cific gravity, iodine value, saponification values and coating prop- erties of the resins were carried out by standard laboratory meth- ods. The system may be used as a potential candidate for coating applications. 1 Research Centre-College of Science, King Saud University, Riyadh 11451, Kingdom of Saudi Arabia 2 Department of Chemistry, College of Science, King Saud University, Riyadh 11451 Kingdom of Saudi Arabia Corresponding author: Manawwer Alam, Research Centre-College of Science, P. O. Box 2455, King Saud University, Riyadh 11451, Kingdom of Saudi Arabia E-mail: malamiitd@gmail.com i 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim www.wiley-vch.de/home/muw