Studying the Effect of Nano Filler on Epoxy Properties used in storage tank Low Carbon Steel Protection

In this study a nano epoxy coating had been prepared to be used for the protection of the internal and external surfaces of storage tank (low carbon steel) from corrosion. A polymeric coating was reinforced with fillers such as red iron oxide, Zinc phosphate and nano titanium dioxide (TiO2) which have been used as anticorrosion. Pieces from low carbon steel was picked from storage tank and coated with two layers, the first layer was prepared from organic polymer (epoxy) with red iron oxide, the second layer was prepared from epoxy with (a nano titanium dioxide and Zinc phosphate). The fillers weight percentages were (0, 7, 10 and 13 % wt). The nano epoxy coating gave good results in limiting the corrosion, the corrosion rate results show that the best percentage of additives was (13,10 % wt) in salt solution 1.0 %wt ( NaCl, Na2SO3 and KCl ).The coating samples were immersed for 3 month at 25 C in gas oil and cutting oil then was characterized using spectroscopic method (FTIR), physical and chemical tests add to characterization of particles size was done by SEM. The samples of TiO2 were characterized by XRD and evaluation of corrosion was made by using static potential test.


Introduction:
Corrosion is one of the most common problems in petroleum industry. It happen mainly in storage tanks and pipelines.Thus considered as the biggest engineering and economic problem in the world [1]. The rate of corrosion is the speed of the metal deterioration in a specific environment. The rate or speed is dependent upon environmental conditions as well as the type, and condition, of the metal. Corrosion is prevented by insulating the metal material from the corrosion agents through the work of a protective layer such as epoxy resin and nano materials that can be used as protective coating for an iron or steel.
Nano fillers widely used in reinforcing the epoxy material to improve the efficiency of the polymeric material performance [2] which is used especially in composites, adhesives and coating as a protective coating for storage tank and pipes surfaces [3], this coating have many properties such as good resistance to chemical materials.

No.29-(12) 2020 Journal of Petroleum Research & Studies (JPRS) E123
The use of nano fillers for anticorrosion coatings has a significant importance. Several researchers have that shown nano fillers perform well in anti-corrosion coatings with polymers and composites [4]. Many nano materials are used as a thin film in petroleum industry such as Al 2 O 3 , SiO 2 , CuO and TiO 2 .Among all nano coatings using TiO 2 considered to be as the most common [5] corrosion protection thin films due to their unique chemical, electrical and optical properties. TiO 2 thin films possess high dielectric constant, wide optical band gap, high refractive index, photo catalytic, low absorption and high transparency with high thermal and chemical stabilities. Titania or titanium dioxide (TiO 2 ) is a semiconductor material, and the best known crystal forms of TiO 2 are the anatase, rutile and brookite [6,7].
While the anatase and rutile, which is a thermodynamically stable phase and is the best known polymorph of TiO2, have the tetragonal crystal system, the brookite has the orthorhombic crystal structure [8].
The anatase and brookite are metastable phases and these are converted the rutile phase after heating [9]. Nano-TiO 2 particles also provide acceptable protection especially for carbon steel and stainless steel [10]. Also, nano materials were used as catalysts in petroleum refining reactors in petroleum refining industry and as coating materials to the storage tanks [11]. TiO 2 nano particles and epoxy resin was applied on low carbon steel surface as coating.
Nano fillers with epoxy can significantly improve the properties of epoxy resin [12], so the reinforcement efficiency is strongly depend on particle size, volume fraction of nanoparticles in epoxy structure and dispersion of nanoparticles [13].
The use of polymeric material such as epoxy resin in the protection of metals is significantly reducing the rate of corrosion. Epoxy resins are the basic material in the coating, these resins are poly ethers contain an epoxy rings at the end of the chain, known as (oxiranes) [14]. Epoxy resins are used in coatings such as protective coating for pipes and the internal surface of tank [15]. It is an excellent adhesive coating, strong, abrasion resistant, and is a good resistance to moisture and chemicals [16]. Composites material is made of (polymer such as epoxy resin) with (fillers such as zinc phosphate and red iron oxide) as a rust resistant layer. It has high adhesion properties on metal [17]. It is suitable for use in marine and petroleum industrial whether immersed or not immersed [18].

No.29-(12) 2020 Journal of Petroleum Research & Studies (JPRS) E124
The main purpose of the polymer coating is to protect the internal and external surfaces of the storage tank (low carbon steel) by using reinforce-ment materials like micro (Fe 2 O 3, Zn 3 (PO 4 ) 2 ) and TiO 2 nanoparticles.

Materials:
The epoxy resin (EP405) was used from Fosroc, Jordan .The ethylene diamine was used as a cross-linking for the epoxy resin. Titanium dioxide nano particles (rutile) purity 99.5% with average particle size a round (30) nm, was obtained from Riedelde Haen, Germany. Micro particles were red iron oxide (Fe 2 O 3 ) and Zn 3 (PO 4 ) 2 by (Cristal Global pharma, France) with particle size (10-25) μm . Castor oil (Iraq) has been added as a plasticizer which improves from the elasticity of polymer coatings. The products were painted on pieces of the metal at thickness (150) microns and left to dry for (7 -10) days.
Gas oil and cutting oil were used from AL-Dora refinary to test the chemical resistance of the coating layer. Chemical analysis of pipeline material (low carbon steel) Wt% (C 0.196%, Mn 0.461% , Si 0.215% , S 0.0173% , P 0.0107% , Fe Balance % low carbon steel were used from the Petroleum Pipeline Company/ Ministry of Oil-Iraq.

Samples preparation method:
The first layer was prepared from organic polymer (EP405) with red iron oxide and hardener. The second layer was prepared from epoxy with a nano titanium dioxide and Zinc phosphate [19]. Hardener was added to mixture. The mixing ratio for (EP405) and the ethylene diamine (hardener) was (3:1). Castor oil was added in a small percentage (0.2) % to each layer. The composite material was mixed at 25ºC using a magnetic stirrer for one hour. The fillers weight percentages were (0, 7, 10 and 13) wt%. All samples componte were coated on pieces of low carbon steel with thickness (150) micron, the samples were left to dry for (7) days. Various salt solutions were prepared at 1.0 wt% for each of (NaCl, Na 2 SO 3 and KCl). Determination of corrosion rate was by weight loss method and the corrosion rate was calculated for each piece using the initial and final weights. The rate can also be calculated as follows [20].

Fig. (1) (FT-IR) spectrum of epoxy resin and nano filler (13 %)
Figure (2) shows the FT-IR spectrum of cutting oil after immersing the coating layer for 3 months, it was observed from the absorption sites that the effective groups of epoxy resin was not shown, indicating that the coating layer has not been affected by the cutting oil and gas oil and it acquired a stability and chemical resistance against these substances.    Crystal size showed as in the listed in table (2), the XRD results showed that the major phase in coating of TiO 2 rutile and epoxy) also were polycrystalline

Table (2) (XRD) test data of samples [2], [3], [4] and [5]
Corrosion Rate: The  Table (3), it can be noticed the Epoxy -TiO 2 composite increased corrosion inhibition with increasing nano TiO 2 weight percentage in tested samples compared with Epoxy-low carbon steel sample. Also, The most effective addition of (TiO 2 ) nano partical was with 13% (sample [4]), with least current corrosion compouned [1] with absence of the nano filler and [5] without coting at all. Also, results show that using the nano TiO 2 weight percentage (7, 10, % wt) in increased corrosion inhibition, as shown in Table (  The results showed that the low carbon steel without coating suffered from little corrosion. While the nanoparticles coating (7,10 and 13) % wt no suffered weight loss because the nanoparticles protected the alloy from corrosion as shown in Figure (9), the weight loss of samples [2][3][4][5] showed in Table (4).  (SEM) Scanning electron microscopic characterization of nano TiO 2 particles, Figure   (10), shows the SEM of nano-TiO 2 with average particle size around (30) nm.

Fig. (10) (SEM) Scanning electron microscopic of nano -TiO 2
The Surface Roughness: The coating layers roughness was measured by surface roughness of material tester, which is the equipment that used to measure the surfaces roughness of material (metal and non-metal) for a distance of 6 mm and the sample dimensions are (1 cm x 1 cm).

Conclusion:
The properties of polymer (epoxy) with filler to configure composites depend on the particles size, shape, interfacial bonding, and surface treatment of the fillers. The dispersion of fillers in polymer matrix has influence on the mechanical ,physical and thermal properties of polymers .The addition of nano fillers (3 ,7,10 )% to epoxy resin cause the increase in the corrosion resistance and polymer nano composites have many advantages over micro composites in the properties such as corrosion resistance bonding strenght. So it is perfect for many uses, as adhesives, protective coating for metal, water pipes and storage tank.