目的 实现室温、大气环境下,以K2TiF6-AlCl3-BMIC离子液体为电解质,电沉积制备致密、较厚的Al-Ti合金镀层,研究电流密度及电解质组分对Al-Ti合金镀层形貌、元素组成及电化学性能的影响。方法 将氟钛酸钾作为AlCl3-BMIC离子液体的钛源,在铜基体上制备Al-Ti合金镀层。采用扫描电子显微镜对不同电沉积条件下制备的Al-Ti合金镀层的形貌和元素组成进行观察。并利用电化学工作站测试Al-Ti合金镀层的电化学性能。结果 当施加的电流密度为20 mA/cm2时,镀层呈树枝晶状;电流密度从15 mA/cm2减小至5 mA/cm2,镀层均呈菱形颗粒,颗粒尺寸逐渐减小。当AlCl3-BMIC离子液体中K2TiF6浓度达0.45 mol/L时,施加10 mA/cm2电流得到的Al-Ti合金镀层Ti含量最高,为19.0%（质量分数）。17.6%（质量分数）Ti的Al-Ti合金镀层在室温25 ℃下,3.5%（质量分数）NaCl溶液体系的自腐蚀电位为-0.565 V（vs.SCE）,自腐蚀电流密度为1.84 μA/cm2,极化电阻值为59 570 Ω·cm2。结论 通过以癸烷为隔绝层的K2TiF6-AlCl3-BMIC离子液体可以在室温、大气环境下电沉积制备Al-Ti合金镀层。降低电流密度可以减小镀层颗粒尺寸,使镀层更为致密。提高氟钛酸钾浓度可以提高Al-Ti合金镀层的Ti含量。对于表面形貌为排列紧密圆胞状的Al-Ti合金镀层,Ti含量会影响镀层的耐蚀性,提高Ti含量,镀层展现出较好的耐蚀性能。
Abstract
Al-Ti alloy coating exhibits superior corrosion resistance, oxidation resistance, and thermal stability. Chloro-aluminate ionic liquid is regarded as the most advantageous electrolyte for the electrodeposition of pure aluminum and aluminum alloy coatings. Aluminum chloride and titanium tetrachloride are frequently utilized as the aluminum and titanium sources for the electrodeposition of Al-Ti alloy respectively. However, aluminum chloride and titanium tetrachloride possess strong hygroscopic properties and are prone to hydrolysis when exposed to air, thereby being unable to deposit Al-Ti alloy. This requires a closed operating environment with an extremely low water oxygen value, which is highly unsuitable for industrial production. We hope to prepare Al-Ti alloy coatings in atmospheric environments at room temperature by replacing the titanium source and using decane which does not react with ionic liquid as the isolation layer, so as to prove the feasibility of ion-liquid electrodeposition of aluminum alloy coating on an industrial scale.
In this work, the dried potassium fluotitanate powder is added into the 66.7-33.3 mol% AlCl3-1-buthyl-3- methylimidazolium chloride ionic liquid and stirred at room temperature for 12 h to obtain K2TiF6-AlCl3-BMIC ionic liquid. At room temperature and in an atmospheric environment, Al-Ti alloy is prepared by electrodeposition on a copper sheet by DC power supply with a double electrode system. A 20 mm × 15 mm × 1 mm pure titanium sheet is used as anode, and a copper electrode is used as cathode. The distance between cathode and anode is 20 mm. Before electrodeposition, the copper electrode is polished to a mirror finish with 40 nm silica suspension after being ground with metallographic sandpaper (e.g. 400#, 800#, 1 500#, 2 000#). The influences of current density and potassium fluotitanate concentration on its composition and morphology are investigated. Finally, the corrosion properties of Al-Ti alloy coatings are tested through an electrochemical workstation, and the coatings with different compositions are compared. The test is performed at room temperature in a 3.5% NaCl (mass fraction) solution.
When the applied current density amounts to 20 mA/cm2, the coating takes on a dendritic form. The current density decreases from 15 mA/cm2 to 5 mA/cm2, and the coating presents a diamond shape with the particle size gradually diminishing. The Ti content of the fabricated dense Al-Ti alloy coating ranges from 2.8 to 19.0wt.%. When the concentration of K2TiF6 in the ionic liquid of AlCl3-BMIC attains 0.45 mol/L, the highest Ti content of the Al-Ti alloy coating obtained by applying a 10 mA/cm2 current reaches 19wt.%. The self-corrosion potential of the Al-Ti alloy coating with 17.6wt.% Ti at room temperature (25 ℃) in a 3.5wt.% NaCl solution system is -0.565 V (vs. SCE), the self-corrosion current density is 1.84 μA/cm2, and the polarization resistance value is 59 570 Ω·cm2.
Reducing the current density can reduce the particle size of the coating and make the coating denser. The Ti content of Al-Ti alloy coating can be increased by increasing the concentration of potassium fluotitanate. The Ti content of Al-Ti alloy coating can affect the corrosion resistance of the coating. Increasing the Ti content in the coating, the coating exhibits excellent corrosion resistance.
关键词
离子液体 /
电沉积 /
Al-Ti合金 /
氟钛酸钾 /
耐腐蚀性
Key words
ionic liquid /
electrodeposition /
Al-Ti alloy /
potassium fluotitanate /
corrosion resistance
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基金
“材料基因工程关键技术与支撑平台”重点专项（2017YFB0702100）
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