氯化铈对镁合金在NaCl溶液中的缓蚀作用

采用电化学阻抗法和动电位极化曲线法研究了氯化铈对镁合金AZ31在3.5％NaCl溶液中腐蚀行为的影响,用扫描电镜(SEM)和能谱仪(EDS)分析了腐蚀产物膜的形貌和成分.结果表明,当NaCl溶液中加入50～200mg/L氯化铈时,镁合金的腐蚀速率均有降低,当稀土含量为l00mg/L时,腐蚀速率最低;加入适当的稀土,腐蚀...     

镁合金阳极氧化膜在NaCl溶液中的腐蚀行为

利用盐水浸泡实验研究了AZ91D镁合金阳极氧化膜层在3．5％NaCl溶液中的腐蚀行为。结果表明：AZ91D镁合金阳极氧化膜层不论封闭与否,在中性NaCl溶液中浸泡出现第一个腐蚀点后,膜层表面均很少再出现新的腐蚀点,而是原有的腐蚀点向纵、横两个方向扩展形成腐蚀坑,表面呈“树枝”状腐蚀形貌;浸泡溶液的pH值对阳极氧化膜层的耐蚀性影响很大,酸性溶液中的腐蚀速率明显大于中、碱性溶液的;随浸泡溶液温度的升高阳极氧化膜层的腐蚀速率加快。据此,提出了AZ91D镁合金阳极氧化膜层在NaCl溶液中腐蚀过程的模型。     

铝合金7A04在干湿周浸条件下的腐蚀行为研究(英文)

采用扫描电镜、X光电子能谱、失重法和电化学交流阻抗技术研究了铝合金7A04在0.6 mol/L NaCl溶液和0.6 mol/LNaCl+0.02mol/L NaHSO3溶液中干湿周浸后的腐蚀行为和规律,并测试了3种材料力学性能的变化.研究结果表明,随试验时间的延长,铝合金腐蚀产物不断增多,腐蚀失重符合指数规律C=A tn,抗拉强度和延伸率呈下降趋势;表面腐蚀产物形貌呈块状,在0.6 mol/L NaCl溶液中腐蚀产物主要为氢氧化铝和氯化铝,而在0.6 mol/LNaCl+0.02 mol/LNaHSO3溶液中腐蚀产物主要为氢氧化铝、氯化铝和硫酸铝.电化学交流阻抗谱显示铝合金7A04在0.6 mol/L NaCI+0.02 mol/0L NaHSO3溶液中的腐蚀速率远大于在0.6 mol/L NaCl溶液的腐蚀速率,并探讨了其腐蚀机理.     

X80管线钢及其焊缝在高温高压环境下的腐蚀性能

采用质量损失法研究了X80管线钢母材及焊缝分别在温度为90 ℃, 压强为4 MPa, 腐蚀介质为0.1 mol/L NaCl+0.4/0.5/0.6 mol/L NaHCO3溶液中浸泡48 h的腐蚀速率,并结合扫描电子显微镜（SEM）和X射线衍射仪（XRD）对腐蚀产物膜的形貌和成分进行了分析。结果表明：X80钢母材及焊缝在0.1 mol/L NaCl+0.5 mol/L NaHCO3溶液中的腐蚀速率最低,此时产生的腐蚀产物膜耐腐蚀性能最好。在该种腐蚀介质中形成的腐蚀产物膜由上、下两层膜组成,上层膜的大小分布不均且易脱落,为Fe(OH)2;下层膜呈颗粒状分布,且均匀致密,为FeCO3。     

X80管线钢及其焊缝在高温高压环境下的耐腐蚀性能

采用质量损失法研究了X80管线钢母材及焊缝分别在温度为90℃,压强为4 MPa,腐蚀介质为0.1 mol/L NaCl+0.4/0.5/0.6mol/L NaHCO_3溶液中浸泡48h的腐蚀速率,并结合扫描电子显微镜(SEM)和X射线衍射仪(XRD)对腐蚀产物膜的形貌和成分进行了分析。结果表明:X80钢母材及焊缝在0.1 mol/L NaCl+0.5 mol/L NaHCO_3溶液中的腐蚀速率最低,此时产生的腐蚀产物膜耐腐蚀性能最好。在该种腐蚀介质中形成的腐蚀产物膜由上、下两层膜组成,上层膜的大小分布不均且易脱落,为Fe(OH)_2;下层膜呈颗粒状分布,且均匀致密,为FeCO_3。     

压铸镁合金AZ91D在碱性NaCl溶液中的腐蚀行为

采用电化学方法研究了压铸镁合金AZ91D在碱性NaCl溶液中的腐蚀行为,并用扫描电镜观察了腐蚀形貌,对腐蚀产物进行了能谱分析.结果表明：在强碱性pH=12的环境下,当Cl-的浓度低于0.1 mol/L时,合金表面可以形成较稳定的钝化膜;随着Cl-浓度的增加,点蚀电位逐渐降低;富Al相的耐蚀性高于基体相,在碱性环境中,腐蚀产物主要为Mg(OH)2和MgO.      

镁合金黑色微弧氧化膜在NaCl溶液中腐蚀电化学演变

目的 评价镁合金黑色微弧氧化热控膜层在氯离子作用下的腐蚀演变行为.方法 在电解液中添加不同浓度的添加剂制备微弧氧化膜层,分析不同微弧氧化膜试样在0.1 mol/L NaCl溶液中的电化学演变过程.采用电化学极化、电化学交流阻抗表征和拟合,结合扫描电镜等方法,对膜层演变规律及机理进行了探讨.结果 未经微弧氧化的镁合金自腐蚀电流密度为17.7 μA/cm2,自腐蚀电位为-1.464 V;经微弧氧化后,试样自腐蚀电流密度减小至0.09 μA/cm2,自腐蚀电位下降至-1.628 V.添加剂加入后制备的微弧氧化膜相比于镁合金基体,其耐蚀性能提高,且随着添加剂浓度的增加,耐蚀效果呈现先增加、后减弱的趋势,添加剂质量浓度在10 g/L时制备的膜层具有最好的防腐效果.镁合金微弧氧化热控膜层在NaCl溶液中腐蚀过程分为三个阶段:一是腐蚀性离子进入多孔膜层,引起界面熔融层变化;二是MgO与水分子反应造成内层膜更加致密,阻抗有所增加;三是腐蚀溶液接触到部分镁合金基底,发生电化学腐蚀,形成楔形效应,引发裂纹,最终导致局部腐蚀失效.结论 微弧氧化提高了膜层的耐蚀性能,其在0.1 mol/L NaCl溶液中的腐蚀过程可分为介质进入孔内、水合反应和局部腐蚀三个阶段.     

MoO42-与 Zn2+对镁合金在 NaCl 溶液中的协同缓蚀作用

采用动电位极化曲线法,结合腐蚀后的表面微观形貌及EDS能谱分析,研究了MoO42-与Zn2+对AZ31镁合金在3.5%NaCl溶液中的协同缓蚀性能。结果表明:0.005 mol/L Zn2+与0.05 mol/L钼酸钠联合作用,可有效抑制镁合金在NaCl溶液中的腐蚀,Zn2+促进MoO42-在合金表面的吸附,缓蚀效果优于单一的钼酸盐缓蚀剂。缓蚀机制是:钼酸盐与Zn2+协同作用,使镁合金表面形成更为致密的钝化膜,从而抑制镁合金的腐蚀。     

X65钢在含超临界CO_2的NaCl溶液中腐蚀机制的讨论

利用高温高压反应釜研究了X65管线钢在含有超临界CO2(supercritical CO2,SC CO2)的3.5%NaCl溶液、去离子水以及溶解有NaCl溶液的超临界CO2相中的腐蚀行为.结果表明,Cl-的存在导致X65钢在含有饱和SCCO2的NaCl溶液中的腐蚀速率显著升高,腐蚀产物膜的晶粒形貌发生改变.X65钢在超临界CO2相中的腐蚀速率远远低于在NaCl溶液中的腐蚀速率,但出现局部腐蚀.X65钢在含有SC CO2的NaCl溶液中的腐蚀分为3个阶段:第一个阶段为基体快速溶解阶段,表面没有FeCO3生成;第二阶段为FeCO3开始沉积阶段,形成的FeCO3腐蚀产物膜不完整,增大了阴极还原反应面积,导致腐蚀加速;第三阶段为腐蚀产物膜保护阶段,形成的腐蚀产物膜致密性逐渐提高,保护性好,但Cl-仍然可以穿过腐蚀产物膜到达膜基界面,从而加速钢的腐蚀.建立了普通管线钢在含Cl-溶液中的超临界CO2腐蚀模型.     

AZ31镁合金在中性NaCl溶液中的电化学噪声研究

采用电化学噪声技术研究了AZ31镁合金在0.1 mol/L中性NaCl溶液中的腐蚀电化学行为,并通过小波分析研究了该体系在腐蚀过程中的腐蚀特征及机理.结果表明:AZ31镁合金在腐蚀之初,由于电极表面覆盖有在空气中形成的离散氧化膜,导致EDP的高阶(低频)能量占据主导地位;同时由于侵蚀性粒子在原始离散氧化膜的缺陷处的攻击,导致与点蚀密切相关的低阶(高频)能量分量在EDP中也占据重要地位;在镁合金的整个腐蚀过程中重复地发生腐蚀产物膜生长、局部剥离和大面积剥离的现象.因此,EDP谱图的特征相应地发生规律性变化：产物膜比较完整时,低频能量分量占据主导地位;腐蚀产物膜局部剥离时,低频能量分量降低,高频能量分量增大;产物膜大面积剥离时,高频能量分量占据主导地位.     

AZ31镁合金沉积类金刚石薄膜的表面形貌和腐蚀行为

为了改善镁合金的耐蚀性,扩展其应用范围,采用等离子全方位离子镀膜技术在AZ31镁合金表面沉积了含有Si-N和Si-O的2种类金刚石(Diamond-like carbon,DLC)薄膜,研究了其表面形貌及其在3.5%NaCl溶液中的腐蚀行为,探究了DLC薄膜对AZ31镁合金腐蚀行为的影响。利用SEM和AFM观察了AZ31镁合金表面沉积DLC薄膜的表面形貌,采用电化学法测试表面沉积DLC薄膜的AZ31镁合金在3.5%NaCl溶液中的极化曲线和开路电位,通过拉伸试验测试其在空气和3.5%NaCl溶液中的应力应变。结果表明:镁合金试样表面的DLC薄膜光滑致密,在3.5%NaCl溶液中表面沉积DLC薄膜AZ31镁合金的极化行为与表面未沉积DLC薄膜AZ31镁合金相似,表面沉积DLC薄膜AZ31镁合金电位正向移动,耐蚀性提高;与表面未沉积DLC薄膜AZ31镁合金相比,在空气中,表面沉积DLC薄膜AZ31镁合金极限抗拉强度与其接近,延伸率略低;在3.5%NaCl溶液中,表面沉积DLC薄膜AZ31镁合金极限抗拉强度略有降低,延伸率略高。     

Corrosion protection of AZ31 magnesium alloy by silane film of partly hydrolysed BTESPT

Abstract

The corrosion protective behaviour of bis-[triethoxysilylpropyl]tetrasulphide (BTESPT) silane film formed by partly hydrolysed BTESPT on AZ31 Mg alloy was investigated. Fourier transform infrared spectroscopy (FTIR) was used for structural characterisation of the silane film. Scanning electron microscope (SEM) and energy dispersive X-ray (EDS) analysis were used for observation of surface morphology and elements analysis of the film. The corrosion behaviours of bare and the silane treated AZ31 Mg alloy in 3·5 wt-%NaCl solution were studied using electrochemical polarisation test, electrochemical impedance spectroscopy (EIS) and immersion test. The results demonstrate that bare AZ31 Mg alloy endures severe corrosion even in NaCl water solution at pH 12, although the corrosion is lighter than that in neutral and acidic NaCl water solution, and that the BTESPT silane film can improve the corrosion protection performances of AZ31 Mg alloy and a lower corrosion rate correlated with higher pH.     

Improvement of corrosion resistance of AZ31 Mg alloy by anodizing with co-precipitation of cerium oxide

Anodizing of AZ31 Mg alloy in NaOH solution by co-precipitation of cerium oxide was investigated. The chemical composition and phase structure of the coating film were determined via optical microscopy, SEM and XRD. The corrosion properties of the anodic film were characterized by using potentiodynamic polarization curves in 17 mmol/L NaCl and 0.1 mol/L Na₂SO₄ solution at 298 K. The corrosion resistance of AZ31 magnesium alloy is significantly improved by adding cerium oxide to alkaline solution. In addition, the surface properties are enhanced and the film contains no crack.     

Enhanced corrosion performance of magnesium phosphate conversion coating on AZ31 magnesium alloy

Magnesium phosphate conversion coating (MPCC) was fabricated on AZ31 magnesium alloy for corrosion protection by immersion treatment in a simple MPCC solution containing Mg²⁺ and PO^3?₄ ions. The MPCC on AZ31 Mg alloy showed micro-cracks structure and a uniform thickness with the thickness of about 2.5 µm after 20 min of phosphating treatment. The composition analyzed by energy dispersive X-ray spectroscopy and X-ray photoelectron spectroscopy revealed that the coating consisted of magnesium phosphate and magnesium hydroxide/oxide compounds. The MPCC showed a significant protective effect on AZ31 Mg alloy. The corrosion current of MPCC was reduced to about 3% of that of the uncoated surface and the time for the deterioration process during immersion in 0.5 mol/L NaCl solution improved from about 10 min to about 24 h.     

镁基牺牲阳极腐蚀行为研究

采用静态失重法、动电位扫描法和交流阻抗法研究了高纯镁和AZ31合金在3.5%NaCl溶液中的腐蚀行为.结果表明：高纯镁在3.5%的NaCl溶液中的平均腐蚀速率要小于AZ31合金,腐蚀后在高纯镁表面形成了一层氧化膜,阻碍进一步腐蚀,而由于第二相与基体发生电化学反应的AZ31合金腐蚀过程继续维持.用SEM观察两者的腐蚀形貌发现,AZ31合金整个表面都被剧烈的腐蚀;而高纯镁表面腐蚀均匀,且腐蚀程度较浅.      

Role of Microalloyed Y and Gd in Improving the Corrosion Resistance of Rolled Mg-3Al-1Zn Alloy

The corrosion performances of rolled AZ31 alloy with addition of Y and Gd were comparatively investigated. The corrosion rates of AZ31 alloy modified with Y and Gd were 3.3 and 3.7 mm/y immersing for 24 h in 3.5 wt% NaCl solution, respectively, which were much lower than that of AZ31 alloy (23.6 mm/y). The remarkable improvement in corrosion performance by adding Y or Gd was ascribed to preferentially form less noble Al₂Y or Al₆GdMn₆ and more protective corrosion product layer, resulting in the reduction in H₂ evolution rate and the enhancement of passivity.     

AZ91D镁合金电偶腐蚀的研究

在自来水和3.5%NaCl溶液中测试了铸造AZ91D镁合金与铝合金、锌合金、Q235碳钢和Cu偶合后的电偶腐蚀行为,研究了腐蚀环境、偶接材料和阴阳极面积比(CAAR)对铸造AZ91D镁合金电偶腐蚀行为的影响。在电偶腐蚀过程中测量溶液的pH值以及电偶腐蚀电流;用失重法计算了铸造AZ91D镁合金的电偶腐蚀速率,利用SEM观察了AZ91D镁合金的腐蚀形貌,并对腐蚀产物进行XRD分析。结果表明,AZ91D镁合金在电偶腐蚀过程中会使溶液的pH值升高,并伴有以Mg(OH)₂为主的腐蚀产物的生成;溶液中Cl^-的存在会加速AZ91D镁合金的电偶腐蚀速率;低氢过电位金属Q235碳钢和Cu对AZ91D镁合金的电偶腐蚀加速效果明显高于中氢过电位金属铝合金和锌合金,偶接材料的极化性能对AZ91D镁合金的电偶腐蚀速率有较大影响。同时,大的阴阳极面积比会加速AZ91D镁合金的电偶腐蚀速率,且AZ91D镁合金的电偶腐蚀电流随阴阳极面积比的增大而呈线性增长趋势。     

AZ31镁合金表面强流脉冲电子束铝合金化研究

利用强流脉冲电子束对AZ31镁合金表面进行快速铝合金化,分析了表面合金化层的显微结构,测量了铝合金化前后,AZ31镁合金的腐蚀性能与耐磨性能.结果表明,经电子束轰击后表层出现了典型的熔坑形貌;耐磨性能测试表明,加速电压为27 kV,脉冲5次的试样比原始试样的相对耐磨性提高6倍,同时合金化也提高了在5%的NaCl溶液中的耐腐蚀性能.     

Formation of a protective layer against corrosion on Mg alloy via alkali pretreatment followed by vanillic acid treatment

Although Mg alloy possesses high specific strength, low density, and good biocompatibility, poor corrosion resistance hinders its further applications. In the present study, an innovative protective layer against corrosion was prepared on the AZ31 Mg alloy via alkali pretreatment followed by vanillic acid treatment. The alkali pretreatment supplied –OH for the AZ31 Mg alloy surface to react with vanillic acid. The vanillic acid treatment played a crucial role in enhancing the corrosion resistance due to the excellent ability to act as a barrier and retard aqueous solution penetration, which effectively isolated the underlying Mg alloy from the corrosive environment. The corrosion current density of alkali and vanillic acid-treated Mg alloy (AZ31V) almost showed two orders of magnitude lower values in comparison with that of the AZ31 Mg alloy, and the corrosion potential of AZ31V Mg alloy increased from −1.41 to −1.25 V. The immersion tests proved that there was no occurrence of severe corrosion. Hence, the alkali pretreatment and vanillic acid treatment may represent a promising method to improve the corrosion resistance of Mg alloy.