环境友好型缓蚀剂对镁合金缓蚀作用的研究

镁合金是最常用的轻金属材料之一,向腐蚀介质中添加缓蚀剂是提升镁合金耐蚀性的有效方法。采用电化学极化和阻抗技术研究了4种吸附型缓蚀剂对AZ91D镁合金在3.5%(质量分数)NaCl中的缓蚀作用;针对该4种吸附型缓蚀剂特性,分别添加了甲磺酸培氟沙星来增强缓蚀剂的吸附性,拟提升其在腐蚀介质中对镁合金的缓蚀性。结果表明,这4种环境友好型缓蚀剂都具有缓蚀作用,甲磺酸培氟沙星的加入能进一步增强对AZ91D镁合金在3.5%(质量分数)NaCl中的缓蚀效果。     

镁合金在NaCl溶液中的腐蚀电化学行为

为了提高镁合金材料的耐蚀性能,用电化学方法对比研究了AZ31,AZ61和AZ91镁合金在3.5%NaCl溶液中的电化学行为及缓蚀剂亚硝酸钠(NaNO2)对AZ61腐蚀电化学行为的影响。结果表明:3种镁合金的腐蚀速度大小依次为AZ31>AZ61>AZ91,其中AZ31的活化性能最高;NaNO2能抑制AZ61的析氢腐蚀速度,腐蚀表面较均匀,腐蚀电流密度J corr降低,腐蚀电位E corr发生正移;NaNO2属于阳极型缓蚀剂,其含量为2.0%时,对AZ61的缓蚀率高达85.1%。     

鞣酸钠对氯化钠溶液中AZ61镁合金的缓蚀作用

过去,通常采用无机缓蚀剂对镁合金进行处理,关于镁的有机物缓蚀剂的报道较少.配制了鞣酸钠缓蚀剂,用极化曲线、交流阻抗技术研究了鞣酸钠对AZ61镁合金在0.5%NaCl中的缓蚀行为.通过扫描电子显微镜(SEM)对腐蚀形貌进行了观测.结果表明:鞣酸钠对AZ61镬合金在0.5%NaCl中有一定的缓蚀效果,其浓度为1.0×10-6mol/L时,缓蚀效果最好;鞣酸分子减弱了腐蚀性Cl-在金属/介质的吸附,其与镁合金表面的腐蚀产物Mg(OH)2构成了一层致密膜,从而较好地抑制了镁合金在介质中的腐蚀.     

AZ31镁合金在含NaCl和Na2SO4薄层液膜下的腐蚀行为

为研究大气污染物对镁合金腐蚀的影响规律,采用室内模拟暴露实验,分析AZ31镁合金含有NaCl和Na2SO4的薄层液膜下的电化学腐蚀行为.结果表明:AZ31镁合金表面沉积NaCl和Na2SO4薄液层中的腐蚀动力学符合幂函数规律,说明NaCl和Na2SO4对AZ31镁合金腐蚀有加速作用;AZ31镁合金在NaCl薄层液膜下,阳极极化电流密度增大,R f和R ct值降低,促进了阴极去极化历程,增强了阳极活性溶解,加剧镁合金的阳极溶解;而在Na2SO4薄层液膜下,R f和R ct值增大,击穿电位与腐蚀电位的差值(ΔE)减小,这是由于难溶的硫酸盐和Mg(OH)2覆盖在AZ31镁合金表面,使金属溶解和离子扩散速率降低,导致阳极过程阻滞.     

O_2/CO_2共存环境下缓蚀剂抑制碳钢腐蚀的机理研究

利用旋转圆盘电极(RDE)研究O_2/CO_2共存环境下,碳钢管线在不同浓度缓蚀剂中的腐蚀电化学行为。通过与CO_2环境中进行对比,研究得到O_2对缓蚀剂抑制碳钢CO_2腐蚀的影响。采用极化曲线测试不同浓度缓蚀剂下的缓蚀效率及阴、阳极行为,利用交流阻抗技术(EIS)监测缓蚀剂的吸附行为及腐蚀过程,并通过EIS拟合出的数据计算并绘制吸附等温线,利用扫描电镜观察含氧条件下的腐蚀形貌,利用XRD分析腐蚀产物膜的成分。结果表明:O_2导致缓蚀剂分子吸附能力减弱,在碳钢表面的吸附量减少,吸附膜覆盖度变小,缓蚀效率明显降低。同时,在有O_2环境下,腐蚀产物主要为疏松多孔的Fe_2O_3和FeO(OH)。由于含氧条件下腐蚀速率增大,腐蚀产物膜生成速率加快,导致缓蚀剂吸附能力进一步减弱,缓蚀剂有效作用时间变短。     

一种新型H2S/CO2缓蚀剂的合成及其性能

国内市场上的大多缓蚀剂在CO2和H2S共存环境下的缓蚀效果较差.为此,合成了一种新型的抗H2S/CO2磷酸酯季铵盐缓蚀剂.采用动态失重、动电位扫描法研究了该缓蚀剂在某油田采出水介质中对碳钢的缓蚀性能,采用扫描电镜(SEM)观察了腐蚀表面.结果表明:磷酸酯季铵盐缓蚀剂是一种阳极型缓蚀剂,在碳钢表面的吸附满足Langmuir吸附等温方程,在(70±2)℃模拟油田水中50 mg/L该缓蚀剂的缓蚀效率达90％,可有效抑制腐蚀.     

薄荷叶缓蚀剂对热轧碳钢的缓蚀作用

为抑制碳钢酸洗时的腐蚀,采用加热回流萃取法从薄荷叶中提取了一种新型绿色缓蚀剂。采用失重法和极化曲线法测试了薄荷叶缓蚀剂在20~50℃时对2 mol/L HCl中热轧碳钢的缓蚀性能。结果表明:薄荷叶缓蚀剂对热轧碳钢的缓蚀效率随其浓度增加而增大,最大缓蚀率达到87.8%;当浓度小于80 mg/L时,温度升高,缓蚀效率减小;浓度大于80 mg/L时,温度升高,缓蚀效率增大;薄荷叶缓蚀剂在热轧碳钢表面的吸附作用符合Langmuir吸附模型;薄荷叶缓蚀剂对热轧碳钢的缓蚀机理为几何覆盖效应,同时抑制腐蚀反应的阴、阳极过程,属于混合型缓蚀剂。     

五羟乙基二乙烯三胺在0.5 mol/L H2SO4溶液中对2024铝的缓蚀性能

为抑制2024铝在硫酸酸洗液中的腐蚀,以二乙烯三胺与2-溴乙醇为主要原料合成了五羟乙基二乙烯三胺(PHT),采用静态失重法、极化曲线法和电化学阻抗谱研究了PHT在0.5 mol/L H2SO4溶液中对2024铝的缓蚀性能,通过扫描电子显微镜进行了腐蚀形貌分析,并通过腐蚀反应动力学和吸附模型探讨了其缓蚀机理.结果 表明:25℃下PHT的缓蚀效率随其浓度的增加而增大,当PHT的浓度为700 mg/L时,其缓蚀效率可达90.85％以上,具有显著的缓蚀性能.PHT的添加显著增大了腐蚀反应的表观活化能,有效抑制了腐蚀反应的进行,是一种以抑制阳极过程为主的混合型缓蚀剂.25℃下PHT在2024铝表面的吸附是物理吸附和化学吸附的混合吸附,且吸附遵循Langrnuir吸附等温模型.     

合金元素Nd对AZ系镁合金牺牲阳极材料耐腐蚀和电化学性能的影响

目前,关于稀土元素Nd对镁合金阳极耐腐蚀性和电化学性能影响的报道较少。向AZ31和AZ63镁合金中加入稀土元素Nd,测试了AZ31和AZ63镁合金加入Nd元素前后在3.5%NaCl溶液中的静态析氢腐蚀速率、失重腐蚀速率、极化曲线和电流效率,观察了镁合金试样的显微组织与腐蚀形貌;研究了合金元素Nd对AZ31、AZ63镁合金牺牲阳极的耐腐蚀与电化学性能的影响。结果表明:合金元素Nd的加入能使AZ31、AZ63镁合金晶粒细化、组织均匀,自腐蚀速率降低、电流效率提高;加入Nd元素后,AZ31,AZ63镁合金的阳极极化没有明显增加。     

以米糠提取液为主料的气相缓蚀剂的缓蚀性能

开发环境友好型缓蚀剂是缓蚀剂技术发展的必然趋势,从天然物中提取有效成分作为缓蚀剂就是途径之一,采用气相缓蚀剂可以有效减轻腐蚀,适应可持续发展的要求.用酸化浸取法从米糠中提取植酸,复配成了气相缓蚀剂;采用失重、极化曲线和阻抗测试等评价了该缓蚀剂的气相缓蚀效率,并对其缓蚀机理进行了初步探讨.结果表明:该缓蚀剂对碳钢的气相腐蚀有良好的缓蚀效果,缓蚀率可达97%;该缓蚀剂为阳极吸附型缓蚀剂,符合Langmuir吸附等温式.     

染色和封孔对铝阳极氧化膜结构和耐蚀性的影响

目前,染色和封孔对铝阳极氧化膜的结构和耐蚀性的影响尚不清楚,且有机染色工艺还不够好。采用200 g/L H2SO4电解液在高纯铝表面制备了综合性能良好的阳极氧化膜,通过含芳香烃的有机偶氮染色剂DLM2203和DLM2707对铝阳极氧化膜进行染色处理,用沸水对染色膜进行封孔处理。采用扫描电镜(SEM)、X射线衍射仪(XRD)、红外光谱仪等分析铝阳极氧化膜及染色膜的表面形貌和相组成,并采用动电位极化曲线、电化学阻抗谱等分析铝阳极氧化膜和染色膜的耐蚀性能。结果表明:铝阳极氧化膜染色均匀,表面平整;染色膜经过沸水封闭处理后,其外观颜色变浅;铝阳极氧化膜经染色处理后,厚度和显微硬度都略有增大;沸水封闭导致染色膜厚度略有增大,而显微硬度减小;铝阳极氧化膜的部分孔洞可被DLM2203染色剂充分吸附而成功染色;DLM2707有机染色剂对铝阳极氧化膜有一定的腐蚀作用;铝阳极氧化膜和2种染色膜的相组成相同;偶氮染料分子可以吸附在铝阳极氧化膜的多孔结构内与表面上;染色膜的腐蚀电流密度相对于高纯铝降低了4个数量级,耐蚀性能较好;铝阳极氧化膜与染色膜的阻抗值均处在同一数量级上,耐腐蚀性能基本相近。     

Corrosion of nickel,iron, cobalt and their alloys in molten salt electrolytes

The processes of high-temperature corrosion, anodic dissolution and passivation of nickel, iron, cobalt and their alloys are reviewed to reveal the progress in understanding the reaction mechanisms defined in the last two decades. In the first part, the procedures of thermodynamical analysis of corrosion processes by potential — pO^2– diagrams are outlined. The second part is devoted to the electrochemical corrosion, anodic dissolution and passivation of the metals studied, the reaction mechanisms and composition of the corrosion layers formed. The effect of the alloying elements on the corrosion resistance and anodic behaviour of the base metal is treated in the third part. A brief summary of the kinetics of the so-called hot corrosion of the studied metals and their alloys in contact with thin molten salt films and aggressive atmospheres is then given. Finally, some conclusions are drawn and some future trends of investigation are indicated.     

Bifurcation structures: Constraints for models of anodic corrosion chemistry

Analysis of the steady state bifurcation structures present in the anodic polarization curves of aluminum identify two significant constraints for any viable model of the anodic corrosion process. These constraints appear in the form of the k-determinacy and codimension of the experimentally observed butterfly catastrophy surface for the anodic region of the polarization surface. Using these constraints it is shown that the “Tafel Law” model of corrosion cannot adequately describe the underlying anodic corrosion chemistry.     

硬铝合金硬质阳极氧化中电解液温度对膜层性能的影响

硬铝合金硬质阳极氧化膜性能优异,但常用的硬质阳极氧化方法存在许多不足.采用硫酸和草酸的混合液作为电解液对硬铝合金硬质阳极氧化,研究了电解液温度对硬质阳极氧化膜厚度、硬度、耐蚀性的影响.结果表明:随着电解液温度的增加,硬质阳极氧化膜的厚度、硬度均先增加后减小;电解液温度为15℃时氧化膜的厚度、硬度最大;硬质阳极氧化膜经重...     

包铝层和氧化时间对2E12铝合金硫酸阳极氧化及膜层性能的影响

对保留表面包铝和去除包铝的2E12-T3铝合金采用硫酸阳极氧化处理工艺,研究了包铝层和氧化时间对铝合金阳极氧化行为及膜层耐蚀性的影响。采用扫描电子显微镜观察氧化膜的表面以及截面形貌,应用动电位扫描极化曲线和电化学阻抗谱对膜层的电化学性能进行分析。结果表明:两种铝合金表面均能形成具有防护性能的阳极氧化膜,膜层随氧化时间延长而增厚。富铜的第二相颗粒会使得不带包铝的2E12铝合金氧化膜具有更多孔洞缺陷,甚至出现微裂纹。保留包铝的2E12铝合金表面氧化膜更厚,孔洞缺陷少,耐蚀性更好。阳极氧化30min和45min的2E12铝合金阳极氧化膜具有较低的腐蚀电流和较高的多孔层阻抗,耐蚀性好。     

Corrosion resistance of the layers formed on the surface of plasma-nitrided AISI 304L steel

Austenitic stainless steels have good corrosion resistance, but their low hardness and low wear resistance limit their use whenever surface hardness is required. Nitriding treatments have been successfully applied to stainless steels to improve their mechanical and tribological properties; however, at temperatures above 723 K, gas or salt bath nitriding processes decrease the corrosion resistance due to the formation of CrN and other phases within the modified layer. Chromium compounds draw chromium and nitrogen from the adjacent regions, degrading the corrosion resistance. The plasma nitriding technique permits the use of treatment temperatures as low as 623 K without promoting degradation in the corrosion resistance of stainless steel. In this work, the pulsed glow discharge (PGD) technique was used for nitriding steel (AISI304L) in order to investigate the effect of the temperature of this treatment in the morphology and, as a consequence, in the anodic behavior of the formed layers, in solution with and without chloride ions. Four different temperatures were employed (623, 673, 723, and 773 K). The samples were characterized by optical microscopy (OM), scanning electron microscopy (SEM) with energy-dispersive spectroscopy (EDS), X-ray diffraction (XRD), microhardness measurements, and electrochemical tests with potentiodynamic anodic polarization curves. The nitriding temperature alters the anodic behavior due to a displacement of the polarization curve towards higher currents, in a solution free of chloride ions. In a chloride solution, the nitriding temperature increases the pitting potential up to the oxygen evolution region.     

Electrochemical corrosion behavior of novel Cu-containing antimicrobial austenitic and ferritic stainless steels in chloride media

The electrochemical corrosion behavior of novel Cu-containing antibacterial austenitic and ferritic stainless steels in 0.05 mol/L NaCl solution has been investigated by dc polarization and ac impedance measurements and compared with that of the conventional stainless steels. Cu was found to particularly affect the kinetics of the anodic reaction. The corrosion performance of the austenite was greatly improved by Cu addition in the studied anodic potential range, whereas Cu effects on the ferrite showed remarkable sensitivity to the applied potential and improved corrosion resistance only in the low anodic potential range. Three-dimensional presentation of the variable-potential impedance data was employed in analyzing the electrochemical corrosion processes and revealed a close relationship between the impedance parameters and the applied potential. The trends of impedance results agree well with those obtained from potentiodynamic polarization measurements.     

Stress corrosion cracking and hydrogen embrittlement cracking of welded weathering steel and carbon steel in a simulated acid rain environment

Abstract

The stress corrosion cracking (SCC) and hydrogen embrittlement cracking (HEC) characteristics of welded weathering steel and carbon steel were investigated in aerated acid chloride solution. The electrochemical properties of welded steels were investigated by polarisation and galvanic corrosion tests. Neither weathering steel nor carbon steel showed passive behaviour in this acid chloride solution. The results indicated that weathering steel had better corrosion resistance than carbon steel. Galvanic corrosion between the weldment and the base metal was not observed in the case of weathering steel because the base metal was anodic to the weldment. However, the carbon steel was susceptible to galvanic corrosion because the weldment acts as an anode. Slow strain rate tests (SSRT) were conducted at a constant strain rate of 7.87 × 10⁷ s^-1 at corrosion potential, and at potentiostatically controlled anodic and cathodic potentials, to investigate the SCC and HEC properties in acid chloride solution. The welded weathering steel and carbon steel were susceptible to both anodic dissolution SCC and hydrogen evolution HEC. However, weathering steel showed less susceptibility of SCC and HEC than carbon steel at anodic potential because of Cr and Cu compounds in the rust layer, which retarded anodic dissolution, and at cathodic potential due to the presence of Cr, Cu, and Ni in alloy elements, which inhibit the reduction of hydrogen ions. SEM fractographs of both steels revealed a quasicleavage fracture in the embrittled region at applied anodic and cathodic potentials.     

钛阳极氧化膜的半导体特性及腐蚀行为

目前,国内外还鲜见有关金属钛阳极氧化膜半导体特性与腐蚀行为的报道。采用极化曲线、交流阻抗和Mott-Schottky曲线研究了TA2硫酸和磷酸阳极氧化膜的腐蚀性能和半导体特性。结果表明：在1％NaCl溶液中,钛阳极氧化膜的自腐蚀电位升高,自腐蚀电流密度降低,耐蚀性能提高;氧化电压对氧化膜的厚度有较大影响;磷酸阳极氧化膜...     

Effect of microstructure on the corrosion behaviour of dental gold alloys

The effect of microstructure on the corrosion behaviour of Au-Cu-11 at % Pd, Au-Cu-11 at % Ag and (Au-Cu-11 at % Ag)-5 at % Pd alloys was studied by anodic potentiodynamic and potentiostatic polarization tests. The single-phase Au-Cu-11 at % Pd alloys had high corrosion resistance and their potentiodynamic polarization curves were simple. The high-nobility Au-Cu-11 at % Ag alloy displayed high corrosion resistance regardless of its microstructure. The two-phase Au-Cu-11 at % Ag and (Au-Cu-11 at % Ag)-5 at % Pd alloys had lowered corrosion resistance compared with the single-phase alloys. Anodic potentiodynamic polarization curves of the two-phase alloys were complex, but they were explained by superimposing the curves of each phase using the principle of additivity. The potential at which the current density sharply increased corresponded with that of each phase, and the value of current density was calculated as the sum of the current density of each phase and taking account of their volume fractions. In the anodic potentiodynamic polarization, there was little galvanic effect between the two phases.