304不锈钢表面TiN涂层的耐蚀性能

目的 提高304不锈钢的耐腐蚀性能.方法 采用磁控溅射技术在304不锈钢表面沉积TiN涂层,并采用SEM、XRD及GDOES对涂层的表面形貌、成分进行测试.通过极化曲线和电化学噪声技术评价TiN涂层和基体在pH=2.5的3.5%(质量分数)NaCl溶液中的腐蚀行为,并研究涂层的失效机制.结果 在304不锈钢表面沉积了厚约1μm且均匀、致密的TiN涂层.极化曲线分析表明,基体和TiN涂层试样出现了自钝化和点蚀现象,其中304不锈钢基体的腐蚀电位为-0.41 V,腐蚀电流密度为8.01×10-6 A/cm2,与之相比,TiN涂层的腐蚀电位(-0.28V)明显增大,腐蚀电流密度(6.34×10-8 A/cm2)显著降低.电化学噪声分析显示,在浸泡初期,TiN涂层电极电流暂态峰数量较少,强度较大,噪声电阻较低,而随着浸泡时间的延长,其电流暂态峰数量增加,强度降低,噪声电阻明显大于304不锈钢基体.腐蚀形貌观察表明,304不锈钢和TiN涂层表面均出现了点蚀.结论 TiN涂层能够明显改善基体的耐蚀性能.TiN涂层主要起物理阻碍作用,涂层的主要失效形式是涂层表面的微观缺陷和破裂.

Corrosion Resistance of TiN Coating on 304 Stainless Steel

Objective To improve the corrosion resistance of 304 stainless steel. Methods TiN coating was fabricated on the surface of 304 stainless steel by magnetron sputtering. The microstructure distribution and chemical composition of TiN coating were characterized by SEM, XRD and GDOES. The corrosion behavior of 304 stainless steel and TiN coatings in 3. 5 wt.% NaCl solu-tion (pH=2. 5) was discussed by polarization curves and electrochemical noise technique. The failure mechanisms of coating was studied according to the electrochemical noise signals, the noise resistance and corrosion morphology. Results The smooth and dense TiN coating with a thickness of about 1 μm was deposited on 304 stainless steel. Substrate and TiN coating showed passiva-tion and pitting in polarization curves, and the values of corrosion potential ( Ecor ) and corrosion current density ( Jcor ) of substrate were-0. 41 V and 8. 01×10-6 A/cm2, respectively. However, for TiN coating the value of Ecor (-0. 28 V)shifted toward the posi-tive, and the value of Jcor (6. 34×10-8 A/cm2) decreased sharply. All the results showed the TiN coating exhibited an excellent corrosion resistance. The results of electrochemical noise showed that the TiN coating revealed fewer transients, higher amplitude current transients and lower noise resistance ( Rn ) at beginning of the testing. However, with increasing immersion time the current transients of TiN coating showed a significant change, and the value of Rn had a sharp increase, compared with the substrate. The corrosion micrograph showed that the pitting occurred on the substrate and TiN coating. Conclusion TiN coating could obviously improve the corrosion resistance of 304 stainless steel. TiN coating acted as the physical barrier, and the corrosion resistance was mainly limited by the pinhole and break.