【作者】 杨伟超；

【导师】 王金淑；

【作者基本信息】 北京工业大学 ， 材料学， 2008， 硕士

【摘要】 暴露在酸性环境和海水环境中的金属非常容易腐蚀,防腐蚀问题亟待解决。近年来,涂层仍是最常用的防腐蚀方法之一,而环保型水性涂料将是未来的发展方向。论文研究了乳液聚合法制备掺杂态聚苯胺及其水性醇酸树脂涂层对低碳钢在模拟海水环境及酸性条件下的防护作用,重点研究了纳米SiO₂及玻璃鳞片的加入对聚苯胺水性醇酸树脂涂层防护性能的影响。通过对比研究不同涂层的极化曲线、交流阻抗、盐雾加速腐蚀、微观结构及元素价态,提出了聚苯胺水性醇酸树脂涂层对低碳钢的腐蚀作用机理。采用乳液法以苯胺单体为原料、（NH4）2SO4为氧化剂、十二烷基苯磺酸为掺杂剂合成了掺杂态聚苯胺,将其与水性醇酸树脂混合制备涂料,并将其涂装于低碳钢表面。通过电化学阻抗、电化学极化曲线分别在3.5%的NaCl和0.5mol·L-1H2SO4电解质溶液中研究其电化学性能及耐盐雾性能。结果表明聚苯胺加入量为5%时,涂料表现出最佳的耐腐蚀性能。相对于未加入聚苯胺的涂层,极化电阻Rp分别高出3个数量级,腐蚀电流低于分别低于3个数量级。在加入聚苯胺5%的基础上,分别加入一定量的纳米SiO₂和玻璃鳞片进行改性研究。结果表明涂层的耐蚀能力大幅增高,且当纳米SiO₂加入量为0.5%、玻璃鳞片加入量为10%时,涂层的综合性能最佳。在NaCl溶液浸泡初期,其极化电阻为8.67×108Ohm,腐蚀电流密度为1.45×10-11 A·cm-2,自腐蚀电位为-0.53V;浸泡800小时后,试样的极化电阻为1.82×106Ohm,腐蚀电流密度为1.62×10-9 A·cm-2,自腐蚀电位为-0.56V。在0.5 mol·L-1 H2SO4中浸泡初期,极化电阻为9.27×108Ohm,自腐蚀电位为-0.52V,腐蚀电流密度为3.08×10-11 A·cm-2。在浸泡1000h后,极化电阻近似为2.68×108 Ohm,自腐蚀电位为-0.46V,腐蚀电流密度为2.34×10-9 A·cm-2,耐盐雾时间为60天,性能与溶剂型涂层相当。对金属基材表面物质进行XPS分析发现在0.5mol·L-1 H2SO4溶液和3.5%NaCl溶液中浸泡过的试样表面有钝化层生成,主要成分为α-Fe2O3和γ-Fe2O3。通过对比测试前后的金属基材的SEM照片中可以发现,3.5%NaCl溶液中浸泡过的试样在钝化层表面出现大量的点蚀孔,而在0.5mol·L-1 H2SO4溶液中浸泡过的试样表面相对其他样品表面分布少量的针孔,电化学性能优良。通过试验总结出聚苯胺在中性和酸性溶液中制钝过程机理,并指出这一过程是一个缓慢的过程,电解液的浸入对钝化层的破坏和钝化层的生成是竞争的过程。更多还原

【Abstract】 It is urgent to solve corrosion problems, as metals are easy to be corrupted in acid circumstance and sea water. In recent years, coating is the most important and economical method of all anticorrosive methods, especially the environmental friendly coating has become the research focus. The coatings including watery alkyd and doped polyaniline synthesized by emulsion copolymerization method to protect mild steel in the artificial sea water and acid circumstance was investigated in this paper. The effects of additives of Nano-SiO₂ and glass flake on the anti-corrosion property of the polyaniline-water watery alkyd coating have been studied.. Based on the experimental data of Polarization curves （Pol）, Electrochemical Impendence Spectrum （EIS）, Salt spray test, microstructure and element analysis, the anticorrosion mechanism of watery alkyd polyaniline coatings was summarizedDoped polyaniline was synthesized from aniline by adding （NH4）2SO4 as oxidant and DBSA as doping agent via emulsion copolymerization method. The production was blended with water alkyd in order to prepare anticorrosion coatings which were spread on the mild steel surface. Electrochemical methods and salt spray were employed to study mild steel blocks with coatings in 3.5% NaCl aqueous solution and 0.5mol·L-1H2SO4 aqueous solution respectively. The result presents the coating obtaining 5% polyaniline has excellent anticorrosion properties. Compared with coatings without polyaniline, polar resistance （Rp） of coatings with 5% polyaniline could increase three orders of magnitude and corrosion current density is lower three orders of magnitude.The nano- SiO₂ and glass flakes were blended in the coatings besides 5% polyaniline and their anticorrosion capability was better than those without nano- SiO₂ and glass flakes. The anticorrosion properties of the coatings （2#） containing 0.5% nano-SiO₂, 10% glass flakes and 5% polyaniline was more excellent than the others. Rp, Ecorro and Icorro of 2# coatings were respectively 8.67×108Ohm and 1.82×106Ohm, -0.53V and -0.56V, 1.45×10-11 A·cm-2 and 1.62×10-9A·cm-1 in 3.5% NaCl aqueous solution initially and after 800h. In the 0.5mol·L-1H2SO4 aqueous solution initially and after 1000h, the coatings′Rp, Ecorro and Icorro are 9.27×108Ohm and 2.68×106Ohm, -0.52V and -0.46V, 3.08×10-11 A·cm-2 and 2.34×10-9A·cm-1 respectively. Salt spray test of the coating was about 60 days. The properities of watery coatings were near to solvent coatings.We found that the mild steel blocks had passivation layer on surface whether samples soaked in3.5% NaCl or 0.5mol·L-1 H2SO4 aqueous solution from XPS. The main phase is properlyα-Fe2O3,γ-Fe2O3 and Fe-PANI complexes. Compared SEM photos before testing with after testing, surface of passivation layer which was soaked in 3.5% NaCl appeared lots of pinholes, but the sample soaked in H2SO4 aqueous solution has a little.The anticorrosion mechanism of polyaniline for mild steel blocks passivated in neutral and acid solution was explored in this paper. The passivation is a slow process and the formation and dissolve of the passivation competitively happened during corrosion process.更多还原