碳纳米管对低锌含量水性环氧富锌漆电化学特性的影响

Effect of carbon nanotube on electrochemical properties of water-based zinc-rich epoxy paint with low zinc content

配制了颜料体积浓度与临界颜料体积浓度之比为1.3的低锌含量水性环氧富锌漆,并通过开路电位(OCP)法、恒电流溶解(GD)法、电化学阻抗谱(EIS)法和电化学噪声(EN)法,研究了加入碳纳米管(CNT)对其涂层在3.5%Na Cl溶液中电化学行为的影响。结果表明,无CNT涂层的OCP始终高于阀电势(-0.81V),只有屏蔽作用,无阴极保护作用,表现出类似Q235钢的EIS图谱,说明吸氧腐蚀发生在铁基体上。其点蚀指数(PI)小于0.1,体系发生均匀腐蚀,且离散度较大。噪声电阻(Rn)随浸泡时间延长一直增大。含CNT涂层既有阴极保护作用又有屏蔽作用,阴极保护时长为40 h。其EIS谱图先类似于纯锌,逐渐接近碳钢的谱图,说明吸氧腐蚀反应先在锌粉表面进行,随浸泡时间延长才逐渐转移到铁基体上。其PI在0.005以下,体系发生均匀腐蚀,离散度较小,Rn先减小后增大。含CNT涂层能为Q235钢提供更好的保护,耐盐水时间延长了24 h。

A water-based low-zinc-content zinc-rich epoxy paint with a ratio of pigment volume concentration to critical pigment volume concentration equal to 1.3 was prepared. The effect of carbon nanotube （CNT） dosage on the electrochemical behavior of its cured film in 3.5% NaCl solution was studied by open circuit potential （OCP） method, galvanostatic dissolution （GD） method, electrochemical impedance spectroscopy （EIS） and electrochemical noise （EN） method. The results revealed that the OCP value of the coating without CNT is always above the valve potential （-0.81V）, which means that it has only shielding effect but no cathodic protection function. Its EIS spectrum is similar to the one presented by Q235 steel, which indicates that oxygen absorption corrosion happens on the iron substrate with a pitting index （PI） value less than 0. I, showing uniform corrosion with big deviation. Its noise resistance （Rn） is increased with the extending of immersion time. The coating with CNT has both cathodic protection and shielding effect, providing about 40 hours of cathodic protection. Its EIS spectrum is similar to that presented by pure zinc firstly and then turned into the one presented by Q235 steel, which implies that oxygen absorption corrosion initially happens on the zinc powder, then gradually transfers to iron substrate with the extending of immersion time. Its PI value is below 0.005, showing uniform corrosion with relatively small deviation. Its Rn is increased initially and then decreased. The coating with CNT can provide better protection for Q235 than that without CNT, showed by the salt water resistance time prolonged by 24 h.