稀土(Ce/La)对碳素钢耐海洋性大气腐蚀影响的电化学研究

稀土元素提高钢铁材料耐大气腐蚀性能的机理已有多种解释,但它本身所具有的缓蚀特性对提高钢铁材料耐候性的机理没有深入研究报道.为此,使用极化曲线、交流阻抗测试、锈层微观分析等方法研究了Ce/La混合稀土对碳素结构钢耐海洋性大气腐蚀性能的影响.结果表明:在中性氯化钠溶液中,钢中加入稀土后自腐蚀电位负移,阴极反应受到阻碍;随着稀土含量的增加,试验钢的锈层变得较为致密,厚度减薄,裂纹和空洞也明显减少,锈层中的电荷传递电阻呈上升趋势,而锈层电阻成下降趋势.对稀土提高钢铁材料耐候性的缓蚀机理进行了讨论.     

Nb对09CuPRe耐候钢在模拟工业大气腐蚀环境下耐蚀性的影响

Nb元素能细化钢的晶粒进而可影响其耐大气腐蚀性能。目前,关于Nb对耐候钢耐腐蚀性能影响的报道较少。在09CuPRe耐候钢中添加Nb元素,冶炼了4种不同Nb含量的耐候钢,于实验室作周期浸润加速腐蚀,以模拟耐候钢在工业大气干湿交替环境中的腐蚀。通过动电位极化曲线、电化学阻抗谱(EIS)和扫描电镜(SEM)等对不同Nb含量耐候钢的耐腐蚀性能进行了研究。结果表明,增大09CuPRe钢中Nb含量可以细化钢的晶粒,提高其耐蚀性能,显著降低其腐蚀速率,提高其自腐蚀电位,使其阳极电流密度减小,腐蚀锈层等效电阻与电荷传输电阻均随Nb含量增大呈上升趋势。     

新型3Ni钢和Q235碳钢、普通耐候钢在热带岛屿大气环境中暴晒后的锈层对比分析

为给高镍钢在热带海洋大气环境下的应用提供一定的数据支撑,通过短期户外暴晒试验对比了热带岛屿大气环境中Q235碳钢、普通耐候钢和新型3Ni钢表面锈层的结构、组成和电化学行为。结果表明:在热带岛屿大气环境中,3Ni钢表现出更低的腐蚀速率,归因于其表面锈层良好的物理结构、合理的元素分布和更低的电化学活性; 3Ni钢锈层平整致密,裂纹孔洞等缺陷较少,能够有效隔绝腐蚀液的进入;内层Ni元素的富集能够更好地抵挡Cl-的入侵,将其阻隔在锈层外侧;而在3.5%NaCl溶液中表现出更大的腐蚀产物膜电阻和电荷转移电阻,有效降低了电化学活性,保持较低的腐蚀溶解过程。因此,相比于Q235碳钢和普通耐候钢,3Ni钢锈层对基体具有更好的保护性,从而降低了在严酷热带岛屿大气环境中的腐蚀速率。     

组织类型对耐候钢耐大气腐蚀性能的影响

目前,有关耐候钢不同显微组织对其耐大气腐蚀性能的影响研究不多.以不同的热处理工艺得到同组分不同组织的耐候钢,通过周侵腐蚀、电化学、锈层微观分析等方法研究了耐候钢在模拟工业大气环境中的腐蚀行为.结果表明:铁素体+珠光体试验钢锈层中缺陷较多,有较多的空洞和裂纹;马氏体钢耐候性优于针状铁素体钢,针状铁素体钢耐候性优于珠光体+铁素体钢;马氏体钢锈层极化曲线的阳极部分受到了阻碍,腐蚀电位正移,耐蚀性得到提高.     

Cr含量对耐候钢耐候性的影响

通过周浸腐蚀试验、电化学测量、锈层微观分析等方法研究了不同Cr含量耐候钢在模拟工业大气环境中的腐蚀行为。结果表明:随着耐候钢Cr含量增加,Cr在锈层中明显富集,促使锈层更加致密,减小了阳极溶解反应电流密度;其表面锈层的电阻Rr及反应电阻Rt均呈增大趋势,锈层的腐蚀电位正移,自腐蚀电流密度减小,极化曲线的阳极部分明显受到了阻碍,从而提高了耐候钢的耐蚀性。     

在盐湖地区暴露48个月纯锌的腐蚀行为

采用X射线衍射(XRD)、扫描电子显微镜(SEM)、金相显微镜和电化学阻抗等手段研究了锌在青海盐湖大气环境(富盐干旱型大气环境)中的腐蚀行为。结果表明,在青海盐湖大气环境中锌的腐蚀规律遵循经验公式m=Atn。锌的向地面比向天面腐蚀严重,向天面暴晒48个月出现锈层脱落现象。两个表面的腐蚀产物均由Zn5(OH)8Cl2·H2O,Zn5(CO)3(OH)6和Zn4SO4(OH)6·3H2O组成,锈层均富含SiO2。电化学结果表明,随着暴晒时间的延长向地面的极化电阻Rp逐渐增大,而向天面的Rp逐渐增加,而暴晒48个月时减小。锈层有抑制基体腐蚀的作用,对两个表面锈层的保护性随暴晒时间的延长而增大,而向天面暴晒48个月时保护性减弱。     

合金元素的二次分配对耐钢抗大气腐蚀性能的影响

根据耐候钢和碳钢大气暴晒的试验结果,讨论了其腐蚀行为和特征,并通过XRD和EPMA分析了合金元素的作用。结果表明,耐候钢相对于碳钢有较好的抗大气腐蚀能力,其中Fe中固溶的合金元素的重新分配促进耐候钢表面保护性锈层的形成。     

Q420NH钢表面锈层稳定化处理与保护性锈层形成分析

采用主要成分为NaHSO₃、FeSO₄、CuSO₄、NiSO₄和Na₂HPO₄的稳定化处理剂对Q420NH钢表面进行稳定化处理,通过干/湿交替循环腐蚀实验(CCT),并借助SEM、EDS和XRD等分析测试手段,对比研究了Q420NH钢稳定化处理与未稳定化处理后表面锈层的显微结构及形成机理。研究结果表明,在64周期的腐蚀实验中,稳定化处理试样的瞬时腐蚀速率高于未稳定化处理试样;稳定化处理试样锈层主要成分为α-FeOOH、γ-Fe OOH、β-Fe OOH和Fe₃O₄/γ-Fe₂O₃,在64周期时,稳定化处理试样锈层中α-FeOOH的含量为28%,较未处理试样增加了50%;稳定化处理的耐候钢试样锈层中,Cr、Ni元素在锈层与基体结合处及锈层内部均有明显富集,锈层的自腐蚀电位由未处理试样的-0.619 V提高到稳定化处理后的-0.530 V,锈层电阻由172Ω·cm2提高到3...     

合金元素的二次分配对耐候钢抗大气腐蚀性能的影响

根据耐候钢和碳钢大气暴晒的试验结果,讨论了其腐蚀行为和行征,并通过XRD和EPMA分析了合金元素的作用,结果表明,耐候钢相对于碳钢有较好的抗大气腐蚀能力,其中Fe中固溶的合金元素的重新分配促进耐候钢表面保护性锈层的形成。     

Q345q桥梁钢和Q345qNH耐候钢在模拟工业大气+除冰盐混合介质中的腐蚀行为

采用干湿循环加速腐蚀实验,研究了Q345qNH耐候钢和Q345q桥梁钢在模拟西北地区工业大气环境的腐蚀介质(除冰盐+0.01 mol/L NaHSO₃)中的腐蚀行为。用失重法研究了两种钢的腐蚀动力学曲线,并使用XRD、SEM 和电化学工作站等手段分析了两种钢腐蚀不同时间后锈层的物相、形貌结构及其电化学特性。结果表明：在除冰盐+NaHSO₃的混合介质中,Q345qNH钢腐蚀100 h前的失重稍大于Q345q钢,腐蚀100 h后桥梁钢的失重量明显大于耐候钢;两种钢的腐蚀产物均由α-FeOOH,β-FeOOH,γ-FeOOH,Fe₂O₃,Fe₃O₄和FeOCl构成,但是Q345q钢中生成的不稳定β-FeOOH和FeOCl的含量明显高于Q345qNH钢,锈层的稳定性降低;随着腐蚀时间的延长两种钢锈层的自腐蚀电位均增大,自腐蚀电流密度均波动性减小,Q345qNH耐候钢的自腐蚀电位增大的速度高于Q345q钢,腐蚀后期其锈层的保护性优于普通桥梁钢。两种钢在混合介质中的腐蚀行为受多离子的耦合效应影响,锈层的致密性因β-FeOOH和FeOCl等不稳定腐蚀产物的生成而降低,但是仍有一定的保护性。Q345qNH耐候钢在除冰盐+0.01 mol/L NaHSO₃混合介质中的耐蚀性优于Q345q普通桥梁钢。     

Effect of rare earth cerium on the impact toughness,corrosion and wear resistance of CrNiMnMo alloyed lining steel

The effects of the addition of rare earth cerium on the impact corrosion and wear resistance of CrNiMnMo alloyed lining steel were studied using metallurgical microscopy, scanning electron microscope, x-ray powder diffraction, a hardness tester, an impact tester, and an impact corrosion abrasion tester. The properties of CrNiMnMo alloyed lining steel with the addition of cerium were compared with that of CrNiMnMo steel without the addition of cerium after being heat treated by same processes. The results show that CrNiMnMo alloyed lining steel with the addition of rare earth cerium consisted of lath martensite with a low residual austenite phase after being quenched and tempered. The lath of the martensite was fine and uniform. The impact toughness and the corrosion resistance of the steel lining board improved greatly with the addition of cerium and the impact toughness increased by 22 % with the fracture mode of being ductile. The CrNiMnMo alloyed lining steel with cerium showed the highest resistance to impact corrosion abrasion compared with the alloy without cerium.     

Effect of chloride ion on corrosion behavior of low carbon steel in 0.1 M NaHCO3 solution with different dissolved oxygen concentrations

The corrosion behavior of low carbon steel in 0.1 M NaHCO_3+ 0.1 M NaCl solution with different dissolved oxygen concentrations was investigated with gravimetric tests and electrochemical measurements.Results show that the corrosion mass loss of steel is remarkably increased with the addition of chloride ion. In the initial stage, the carbon steel tends to active dissolution due to the dissolution effect of chloride ion on the oxide film; as a result, the corrosion potential maintains as low values. With the immersion time going by, the corrosion potential of the steel is promoted as a result of the accumulation of the corrosion products. However, the rust layer is loose and porous due to the deteriorating effect of chloride ion, which decreases the reduction resistance of oxygen. Meanwhile, the porous rust layer could be repaired by the depolarization of oxygen. Under the synergistic effect of chloride ion and oxygen, the corrosion of the steel is accelerated during the repeated process of dissolution and reparation of the oxide film.     

Synthesis of corrosion inhibitive poly(2,5-dimethylaniline) coatings on low carbon steel

An attempt has been made towards the synthesis of strongly adherent poly(2,5-dimethylaniline) coatings on low carbon steel substrates, with an objective of examining the possibility of using this polymer for corrosion protection of steel in chloride environment. In this work, the poly(2,5-dimethylaniline) coatings were synthesized by electrochemical polymerization of 2,5-dimethylaniline using sodium salicylate as a supporting electrolyte. The characterization of these coatings was carried out by cyclic voltammetry, UV-visible absorption spectroscopy, Fourier transform infrared spectroscopy and scanning electron microscopy. The results of these characterizations indicate that the aqueous salicylate solution is a suitable medium for the electrochemical polymerization of 2,5-dimethylaniline to generate strongly adherent and smooth poly(2,5-dimethylaniline) coatings on low carbon steel substrates. The performance of poly(2,5-dimethylaniline) as protective coating against corrosion of low carbon steel in aqueous 3% NaCl was assessed by the open circuit potential and the potentiodynamic polarization measurements. The potentiodynamic polarization measurement reveals that the poly(2,5-dimethylaniline) coating increases the corrosion potential and reduces the corrosion rate of low carbon steel almost by a factor of 50. This study clearly ascertains that the poly(2,5-dimethylaniline) has outstanding capability to protect low carbon steel against corrosion in chloride environment.     

含稀土1Cr18Ni9Ti不锈钢焊接接头耐腐蚀性能的电化学研究

通过焊条药皮向１Ｃｒ１８Ｎｉ９Ｔｉ不锈钢焊缝中过渡稀土,用高温电化学方法研究了稀土对焊缝耐内蒙古天然碱苛化烧碱腐蚀性能的影响。结果表明：采用适量的焊条药皮配方和焊接工艺可使稀土元素过渡到焊缝金属中,适量稀土元素改变了不锈钢焊接接头阳极极化曲线的极化度,从而改善了不锈钢材料焊接接头的耐蚀性。     

稀土处理对Mn-V-Ti钢点蚀性能影响的研究

实验室冶炼了5炉稀土处理及未处理的锰系低合金船体钢,并收集了一种工业生产的同种钢。通过冶金分析、极化试验、闭塞电池试验及挂片试验,研究了夹杂物变性对钢材点蚀诱发及扩展的影响;结果表明:钢中夹杂物是点蚀的诱发源,硫化物夹杂物的数量对钢材的点蚀性能有显著影响。稀土硫化物夹杂数量少,体积小,能显著降低钢的点蚀诱发敏感性,降低钢的蚀坑扩展速度,提高钢的耐蚀性。     

稀土元素(La,Ce)对镁合电偶腐蚀的影响

针对镁合金化学和电化学活性较高,与其他金属材料接触时易产生电偶腐蚀的特点,主要研究了其电偶腐蚀特性及环境因素的影响规律.采用电化学方法通过测定电偶电流密度,研究了添加约1%混合稀土RE(45%La,50?)的AZ91合金在NaCl溶液中与A3钢、紫铜偶接时的电偶腐蚀行为,探讨了溶液中氯离子浓度、偶接金属种类以及阴阳极面积比对电偶电流密度JgMg的影响.结果表明:Cl-浓度增大,JgMg变大;阴阳极面积比越大,JgMg也越大;偶接金属A3钢比紫铜更易促进镁合金的腐蚀;稀土La,Ce的添加使电偶腐蚀有效距离变窄.     

变电站接地电极的腐蚀与防护研究

为了研究变电站接地网在降阻剂中的腐蚀情况,用化学分析的方法测试了变电站的土壤和所用降阻剂的理化性质,用失重法分析了除去镀锌层后的A3钢电极在土壤和降阻剂中的腐蚀情况.试验结果表明, A3钢电极在弱碱性降阻剂中的腐蚀比在中性土壤中的腐蚀严重,主要原因是降阻剂中含有Cl-使降阻剂成为一种强腐蚀性介质,造成了电极的点蚀穿孔.通过动态恒电位扫描法测定A3钢在各种溶液中的极化曲线以获得各离子对电极的自腐蚀电位和孔蚀电位的影响,结果表明在降阻剂中加入缓蚀剂,如磷酸盐和硅酸盐,可以缓解降阻剂中Cl-对A3钢的点蚀影响,使降阻剂既能降低接地电阻又可缓解接地网的腐蚀.     

具有剥离涂层缺陷低碳钢的阴极极化特性

为探索具有剥离涂层缺陷低碳钢的腐蚀规律与机理,将环氧煤沥青作为涂层材料,对Q235钢人为模拟制作了面积比例为4.91%的大块剥离涂层缺陷,并采用交流阻抗技术研究了剥离涂层缺陷对Q235钢于3.5%NaCl水溶液中的腐蚀特性和阴极保护效果的影响.结果表明,在较短的浸泡时间和阴极极化电位下,涂层缺陷下方金属基体的腐蚀程度低于在自然腐蚀电位下的腐蚀程度,但在较长的浸泡时间里,阴极极化状态与自然腐蚀状态下金属基体具有相似的腐蚀程度及腐蚀特性,这说明在电解质溶液大量浸入涂层后将严重降低阴极保护的作用,涂层下金属与电解质溶液间的缝隙腐蚀是导致阴极保护效果降低的主要原因.     

Effects of bentonite content on the corrosion evolution of low carbon steel in simulated geological disposal environment

The effects of bentonite content on the corrosion behavior of low carbon steel in 5 mM NaHCO3+ 1 mM NaCl + 1 mM Na2SO4 solution were investigated by electrochemical measurements combined with X-ray diffraction(XRD) and scanning electron microscopy(SEM). In the initial immersion stage, the cathodic process of low carbon steel corrosion was dominated by the reduction of dissolved oxygen, while it transformed to the reduction of ferric corrosion products with the immersion time. The presence of bentonite colloids could suppress the cathodic reduction of oxygen due to their barrier effect on the diffusion of oxygen. However, the barrier performance of bentonite layer was gradually deteriorated due to the coagulation and separation of bentonite colloids caused by the charge neutralization of iron corrosion products dissolved from the steel substrate. More bentonite colloids could maintain the barrier effect for a long time before it was deteriorated by the accumulation of corrosion products. Conversely,it could lose the performance completely, and the corrosion behavior of low carbon steel reverted to the same as that in the blank solution.     

高pH值的硝酸铀酰溶液中碳钢腐蚀与沉积膜的特性

用均匀腐蚀法和电化学法研究了碳钢(A3)在pH值5.0的硝酸铀酰溶液中的腐蚀行为。均匀腐蚀试验结果表明，碳钢在PH值5．0硝酸铀酰溶液中发生非电化学腐蚀，使溶液酸度降低，导致铀酰离子水解，在碳钢表面形成了水合氧化铀沉积膜。动电位阳极极化试验结果显示，碳钢的腐蚀电位随扫描电位速率的增加向阴极方向移动，UO2^2 的沉积对碳钢的阴极反应有抑制作用。均匀腐蚀后的样品，经XRD、XPS分析证实，沉积膜主要为铀酰离子的氧化物沉淀。