碳钢表面磷酸镁防腐涂料的制备及改性研究

Study on Preparation and Modification of Magnesium Phosphate Anticorrosive Coatings on Carbon Steel

磷酸镁水泥(MPC)涂料对碳钢具有良好的防腐能力,但需要对金属基体进行磷酸盐转化等预处理,影响其实际应用。本研究用氢氧化镁部分替换MPC原料中的重烧氧化镁,涂覆Q235钢表面。采用扫描电镜、X射线衍射表征涂层形貌与成分,通过线性极化法、电化学阻抗谱、中性盐雾试验和动电位极化法分析涂层的耐腐蚀性能及其防护机理。结果表明:添加6%(质量分数)氢氧化镁的MPC涂层能够有效抑制涂层-金属界面析氢,且具有更好的耐腐蚀性能。试样浸泡在3.5%NaCl溶液中14 d涂层性能保持稳定,线性极化电阻维持在104Ω·cm^2数量级,耐盐雾超过2400 h。动电位极化曲线表明,MPC涂层具有物理隔离与化学缓蚀双重防护机制。

Magnesium phosphate cement(MPC)coatings can provide good corrosion protection for carbon steel.But it needs a pretreatment for conversion of phosphate,reducing its practical application.This article described the replacement of dead-burned magnesium oxide in the magnesium phosphate cement(MPC)coatings formulation partly with magnesium hydroxide.Coatings morphology and phase composition were characterized by scanning electron microscopy and X-ray diffraction.Corrosion resistance and anti-corrosive mechanism of the coatings were tested by linear polarization,electrochemical impedance spectroscopy,neutral salt spray test,and potentiodynamic polarization.Results showed that,at a replacement of 6%magnesium hydroxide,the MPC coatings prepared provided better corrosion resistance and effectively inhibition of hydrogen evolution at the coatings-metal interface.During immersion in 3.5%Na Cl solution for 14 d,the Rpof MPC-coated samples remained at 104Ω·cm^2 level.The samples was rust-free after salt spray test for 2400 h.The MPC coatings had a dual protective mechanism of physical barrier and chemical corrosion inhibition.By optimizing the coatings formulation,phosphating pretreatment was eliminated and the process was simplified.The corrosion resistance of MPC coatings was also improved.