Ashraf M. El-Saeed et al Int. Journal of Engineering Research and Applications www.ijera.com ISSN : 2248-9622, Vol. 4, Issue 11(Version - 5), November 2014, pp.65-73 www.ijera.com 65 | Page f A new double layer epoxy coating for corrosion protection of Petroleum Equipments Maher A. El Sockary a , Ashraf M. El-Saeed a , Samya I. El Sherbiny b , Fatma A. Morsy b , Ehab A. Dawood c and Mohamed A. ELleithy b, c a Petroleum Applications Department, Egyptian Petroleum Research Institute, Nasr City 11727, Cairo, Egypt . b Helwan University, Faculty of Science, Chemistry Department, Helwan, Egypt. c Egyption town gas company, Giza, Egypt. ABSTRACT Homogeneous epoxy coating containing polymer nanocomposite (PNC) was successfully synthesized and applied on carbon steel substrates by room temperature curing of fully mixed epoxy slurry. (PNC) containing both ZNO nanoparticles and epoxy hyper branched polymer (EHBP), a new double layer thin film which comprises ZNO-epoxy as a primer coat and ZNO-EHBP-epoxy as a top coat offers better corrosion protection compared to the purely inorganic ZNO-epoxy coating and hybrid ZNO-EHBP-epoxy coating. Chemical structures of synthesized compounds were confirmed by FTIR, H 1 NMR spectroscopy and GPC. The surface morphology and phase structure of the produced Zno nanoparticles were characterized by scanning electron microscopy SEM, transmission electron microscopy TEM and X-ray diffraction. Chemical resistance of theses coatings to NaOH and HCL was investigated. The effect of incorporating polymer nanocomposite and new double layer coating on corrosion resistance of epoxy coated steel was investigated by salt spray test. Keywords: double layer coating, Epoxy coatings, Hyper branched polymers, polymer nanocomposites, ZNO nanoparticles. I. INTRODUCTION Epoxy has been widely used as a coating material to protect the steel structures [1–3], because of its outstanding process ability, excellent chemical resistance, good electrical insulating properties and strong adhesion to heterogeneous materials. Epoxy coatings generally reduce the corrosion of a metallic substrate subject to an electrolyte in two ways: First, they act as a physical barrier layer to control the ingress of deleterious species. Second, they can serve as a reservoir for corrosion inhibitors to aid the steel surface in resisting attack by aggressive species such as chloride anions. Nonetheless, the successful application of epoxy coatings is often hampered by their susceptibility to damage by surface abrasion and wear [4, 5]. They also show poor resistance to the initiation and propagation of cracks [6], such processes introduce localized defects in the coating and impair their appearance and mechanical strength. The defects can also act as pathways accelerating the ingress of water, oxygen and aggressive species onto the metallic substrate, resulting in its localized corrosion. Furthermore, being hydrophobic in nature, epoxy coatings experience large volume shrinkage upon curing and can absorb water from surroundings [7, 8]. The pores in the cured epoxy coating can assist in the migration of absorbed water and other species to the epoxy–metal interface, leading to initiation of corrosion of metallic substrate and delamination of the coating. The barrier performance of epoxy coatings can be enhanced by incorporation of a second phase that is miscible with epoxy coating. incorporation of zinc oxide nanoparticles into epoxy resins offers environmentally benign solutions to enhancing the integrity and durability of coatings, since the fine particles dispersed in coatings can fill cavities, decreasing the porosity, zigzagging the diffusion paths for deleterious species [9–11] and cause crack bridging, crack deflection and crack bowing [12]. Nanoparticles tend to occupy small hole defects formed from local shrinkage during curing of epoxy resin and they act as a bridge interconnecting more molecules. This results in a reduction of total free volume and grain boundaries size, as well as an increase in the cross-linking density of epoxy resin matrix, so that the trend of coating to blister or delaminate is reduced [13 - 16]. The main problem with Incorporation of inorganic nanoparticles into an epoxy polymer matrix is the prevention of particles aggregation. It is difficult to produce mono dispersed nanoparticles in an epoxy polymer matrix because of agglomeration nanoparticles due to their high specific surface area and volume effects, which lead to lower dispersion stability in epoxy resin, in addition to incorporation of RESEARCH ARTICLE OPEN ACCESS