Fe <sub> 3 </ Sub> O <sub> 4 </ Sub> / Conductive Polymer Composites Synthesis And Anti-corrosion Anti-wax Performance

The corrosion and paraffin deposition of the pipeline were two important factors which restricted the security and efficiency of gas and oil transportation. Corrosion damages in pipeline caused crude oil leakage even explosions and the paraffin deposition required to remove regularly, both seriously affected the transportation efficiency. Can we prepare a kind of multifunctional internal coating which had the functions of anticorrosion paraffin controlling? A bold exploration was done in this paper. A composite of Fe3O4 and conducting polymers was synthesized and added into alkyd varnish to form a composite coating. After investigated the anticorrosion and paraffin controlling performance, this composite coating was demonstrated to be feasible for internal coating of pipelines. Specific researches were list as follows:(1) Fe3O4 was synthesized by co-precipitation method, using the FeCl3 and FeSO4 as iron sources, NH3·H2O and N2H4·H2O as precipitant system. The optimal condition were obtained, mole ratio of Fe3+:Fe2+was 1.75:1, reaction temperature was 70℃. FT-IR and XRD analysis showed that the product was pure and had typical anti-spinel structure with grain size of about 10nm. Vibrating sample magnetometer (VSM) analysis showed that the saturation magnetic field intensity per unit mass was 61.143emu/g. The modification of Fe3O4 showed that sodium dodecylbenzene sulfonate (SDBS) had a good modification effect, and the modified Fe3O4 aqueous solution dispersed well and was not hierarchical. The investigation of laser particle size analyzer showed that SDBS had significant regulatory effect to the particle size of Fe3O4, combined with FT-IR and Zeta potential analysis, it could figure out that the reason was O-O covalent bond between SDBS and Fe3O4.(2) Base on the synthesized Fe3O4, the composite of Fe3O4 and PTH (polythiophene) was prepared and investigated with Raman, FT-IR, EDS, TEM, Zeta and TG-SDTA. The results showed that the thiophene was successfully polymerized on the surface of Fe3O4 and the resulting composite was in the nature of core shell structure, in which the core was Fe3O4 with particle size of 14nm and the shell was PTH with thickness of 3-4nm. The composite coating was obtained with the Fe3O4/PTH composite added into alkyd varnish. Accelerated corrosion test and static paraffin control test showed that the composite coating had good performances of anticorrosion and paraffin controlling, when the mass ratio of Fe3O4/PTH composite was 0.8-1%, and the Paint adhesion and impact test results showed that the added Fe3O4/PTH composite had no influence to the adhesion, while the impact strength decreased slightly.(3) In order to increase the paraffin control performance, the Fe3O4 was doped with Ni and formed Ni doped Fe3O4/PTH composite. XPS analysis showed that the doped content was 0.8%in the composite. VSM analysis showed that the saturation magnetic field intensity per unit mass of the composite was 73.456emu/g, increased 20.14%compared with the undoped Fe3O4. To simulate the paraffin deposition, the solid paraffin was dissolved into the liquid paraffin, and the wax precipitation point was 40℃determined by rotational viscometer when the mass ratio of solid paraffin was 20%. At the temperature of wax precipitation point, the test plate coated with composite coating was immersed into, pulled out and weighted the weight increments again and again. The results showed that the average weight increment of alkyd varnish was 89.1mg, and that of composite coating added with Fe3O4 was 80.3mg and that of composite coating added with Ni doped Fe3O4/PTH was 74.3mg, indicating the composite coating added with Ni doped Fe3O4/PTH had the best paraffin controlling performance because the weight increments were the paraffin deposited on the test plates.(4) To verify the anticorrosion effectiveness of Ni doped Fe3O4/PTH composite, the comparison was carried out to the market applicated ployaniline (PANI). So the Ni doped Fe3O4/PANI composite was prepared. The electrochemical impedance spectroscopy (EIS) showed that the anticorrosion performance of Ni doped Fe3O4/PTH was comparable to the Ni doped Fe3O4/PANI.