Yin Siyi, Yang Haiyan, Dong Yinghao, Qu Chengju, Liu Jinghui, Guo Tailin, Duan Ke
School of Materials Science and Engineering, Southwest Jiaotong Univesity, Chengdu, 610031, Sichuan, China.
Sichuan Provincial Laboratory of Orthopaedic Engineering, Department of Bone and Joint Surgery, Affiliated Hospital of Southwest Medical University, Luzhou, 646000, Sichuan, China.
Sci Rep. 2021 Jan 8;11(1):197. doi: 10.1038/s41598-020-79613-3.
Polymer coatings are commonly used to protect carbon steels from corrosion but they are susceptible to weathering and many of them have environmental concerns. Therefore, we studied the possibility of an environmentally favorable inorganic magnesium phosphate cement (MPC) coating for protecting mild steel. A formulation suitable for coating steel was developed by compositional modification [i.e., incremental replacement of dead-burned magnesia (MgO) with magnesium hydroxide (Mg(OH))] to a road-repair MPC. This modification yielded an acceptable working time and prevented pore formation at the coating-steel interface. Corrosion monitoring by linear polarization and electrochemical impedance spectroscopy for 14 days found that, the MPC coating substantially increased the linear polarization resistance (R) [e.g., day 1: (8.2 ± 1.7) × 10 (nadir value) vs. 495 ± 55 Ω cm] and charge transfer resistance (R) (e.g., day 1: 9.3 × 10 vs. 3.8 × 10 Ω cm). The coated steel underwent neutral sodium chloride (NaCl) salt spray for 2400 h without visible rusting. Immersion for 24 h in liquids simulating the pore fluid indicated that, passivation by the excess MgO in the coating was a major contributor to its anti-corrosive property. Tafel polarization in the liquids found that, corrosion current density (I) followed the rank: 3.5% NaCl solution (6.0 µA cm) > 3.5% NaCl solution containing MgO (3.6 µA cm) > 3.5% NaCl solution containing fragmented MPC (1.7 µA cm), suggesting that a physical barrier effect and dissolved phosphate ions improved its protection. This study shows that, MPC coating is a promising durable and environmentally favorable anti-corrosive material for protecting steel structures in some applications.
聚合物涂层通常用于保护碳钢免受腐蚀，但它们易受风化影响，并且其中许多存在环境问题。因此，我们研究了使用对环境有利的无机磷酸镁水泥（MPC）涂层来保护低碳钢的可能性。通过对道路修复用MPC进行成分改性（即用氢氧化镁（Mg(OH)₂）逐步替代死烧氧化镁（MgO）），开发出了一种适合涂覆钢材的配方。这种改性产生了可接受的工作时间，并防止了涂层与钢材界面处形成孔隙。通过线性极化和电化学阻抗谱进行了14天的腐蚀监测，发现MPC涂层显著提高了线性极化电阻（Rₚ）[例如，第1天：(8.2 ± 1.7)×10⁻⁶（最低点值）对495 ± 55 Ω·cm²]和电荷转移电阻（Rct）（例如，第1天：9.3×10³对3.8×10⁴ Ω·cm²）。涂覆的钢材在中性氯化钠（NaCl）盐雾中暴露2400小时无明显生锈。在模拟孔隙液的液体中浸泡24小时表明，涂层中过量的MgO引起的钝化是其防腐性能的主要贡献因素。在这些液体中进行的塔菲尔极化发现，腐蚀电流密度（Icorr）的顺序为：3.5% NaCl溶液（6.0 μA/cm²）＞含MgO的3.5% NaCl溶液（3.6 μA/cm²）＞含破碎MPC的3.5% NaCl溶液（1.7 μA/cm²），这表明物理屏障效应和溶解的磷酸根离子改善了其防护效果。本研究表明，MPC涂层在某些应用中是一种有前景的耐用且对环境有利的防腐材料，可用于保护钢结构。
