Electrochemical Performance Study of Rust Layer on Cu-P-RE Weathering Steel

Corrosion rates of 10PCuRE steels with different rate earth contents and plain carbon steel were studied by dry-wet cycle immersion test. The corrosion resistance of rust layer on rare earths weathering steel and carbon steel was studied through the electrochemical means of polarization test and electrochemical impedance spectra. The difference of corrosion resistance of testing steels was analyzed through electrochemical means. The 10PCuRE steels whose rare earths content is smaller than 0.016% have good performance of corrosion resistance because corrosion potential of the steel is positive and resistance of rust layer is large. The results showed that rare earths of proper content could diminish corrosion tendency and promote the formation of the steady and compact rust layer.

STUDY ON RUST LAYERS ON STEEL IN DIFFERENT MARINE CORROSION ZONE

The Mossbauer spectra for corrosion products formed on A3 ds steel and low alloy 16Mn steel exposed in the Chengdao sea area for 2 years by the electro- connected method were determinal. The phase composition and content of the rust layers on the two steels in four marine corrosion zones were analyzed and studied. Although the phase composition of the two steels were different, their main phase was β-FeOOH. The different content of FEOOH and Fe3O4 in the rust layers illustrated that FeOOH in the inner rist layer participated in the cathodic process as an oxidant accelerating the corrosion rate of steel under wet/ dry cycle condition. Moreover, for the alloy elements in 16Mn steel, the rust layers with simple composition and fine and close texture formed a good barrier layer lowering the corrosion rate of low alloy steel.

Effect of trace boron on corrosion resistance of rust layer of high-strength low-alloy steel in 3.5 wt.% NaCl solution

The influence mechanism of trace boron on the corrosion resistance of high-strength low-alloy(HSLA)steel in a simulated marine environment was studied by combining first-principles calculation with experiment.The effect of boron on the corrosion properties and corrosion morphology of the rust layer formed on the surface of HSLA steel was studied by means of corrosion weightlessness method,polarization curve,scanning electron microscopy(SEM)and X-ray diffraction(XRD)technique.The mass loss measurements and polarization curves revealed that the corrosion resistance of HSLA steel is improved by adding trace boron.XRD and SEM results show that the rust layer is produced byα-FeOOH(the main protective phase),Fe_(3)O_(4) andγ-FeOOH,and boron contributes to stability ofα-FeOOH.Based on the first-principles calculation,the solid solution of B atom in the corrosion product is beneficial to the fixation of Cl atom and to the reduction of the corrosion of Cl atom to the steel matrix.

A Study of Rust Layer of Ultra-Thin Cast Strip Steel Containing 0.10%Sb in Simulated Industrial Atmosphere

A new type of steel containing Sb based on the CASTRIP process had been designed to improve the corrosion resistance of high-strength steels in industrial atmospheres.The properties of the electrochemistry and rust layer(RL)were analyzed to evaluate the corrosion resistance of the ultra-thin cast strip(UCS)steel containing 0.10%Sb.Experimental results showed that the corrosion resistance of UCS steel containing Sb was doubled compared to that of traditional hot rolling strip(HRS)steel.It could be interpreted as an integral effect of CASTRIP process and alloying elements.The optimization for microstructure and inclusion of UCS steel can reduce the localized corrosion effects in initial corrosion processes.Cu,P and Sb reduced the anodic reaction and CuFeO2/Cu2O,CuO,FePO4 and Sb2O3 were formed,promoting the transition fromγ-FeOOH toα-FeOOH.A(Cu,Sb,P)-enriched inner RL was generated and significantly improved protective ability of the RL.

Stabilization technology and corrosion mechanism of rust layer on Q370 weathering steel surface

A newly developed rust layer on Q370qENH weathering steel(sample C)was studied under dry–wet cycle test of 3.5 wt.%NaCl solution and salt spray test,compared with the bare weathering steel(sample A)and the weathering steel with additive contents(CuSO_(4)0.2,FeSO_(4)0.1,NaHSO_(3)0.02,NaCl 0.02,Na_(2)HPO_(4)0.01,and water balance,in mass%,termed as sample B).Corrosion mechanism of Q370qENH weathering steel after different surface treatments was investigated by means of surface potential scanning,mass change,polarization curve,and X-ray diffraction.The results of X-ray diffraction indicate that rust of bare weathering steel has rare Fe_(3)O_(4),and a dense oxide layer mainly composed of Fe_(3)O_(4) is formed on rust of both sample B and sample C.The surface potential of sample A gradually increases to−0.2 V in the dry–wet cycle test,while the surface potential of sample A maintains at about−0.6 V in the salt spray test.The surface potential of sample B and sample C is higher than that of sample A in the early stage and remains stable during the short-term accelerated corrosion test.Moreover,the mass change of sample C gradually stabilizes with time in the dry–wet cycle and salt spray test.The corrosion current of the sample A is lower than that of sample C in the initial stage of short-term accelerated corrosion test.However,the corrosion current of sample C is smaller than that of the sample A in the experiment.The main components of the deep rust of sample A areγ-FeOOH andα-FeOOH,while those of the deep rust of sample B and sample C are Fe_(3)O_(4).

Evolution of the Rust Layers Formed on Carbon and Weathering Steels in Environment Containing Chloride Ions

To clarify the correlation between alloy elements and growth pattern of the rust layers, the rusting evolution of the carbon and weathering steels was investigated by using the gold markers method. The corrosion experiments were carried out in a simulated environment containing chloride ions. The results indicate that Ni, Cu, Cr and Mo elements in the weathering steel suppress the rust crystallization and impede the rust layer growth to an internal development, and the suppression function benefits the formation of a protective rust layer. Moreover, c-FeOOH is mainly located in the outer rust layer, while b-FeOOH is mainly located in the inner rust layer, and the distribution of the rust compounds in the rust layer is closely related to the growth pattern of the rust layer.

Characterization of Compactness of Rust Layers on Weathering Steels by an Adsorption/Dehydration Test of Ethanol

A new method for evaluating the compactness of rust layers on steels has been proposed in the present study. The method includes adsorption and dehydration process of anhydrous ethanol. The protective ability of rust layers can be qualitatively reflected by the adsorption/dehydration rates. The specific surface area and porosity of rust layers can be calculated by a quantitative model. The results from the present method are consistent with electrochemical tests, N2 adsorption and X-ray diffraction analysis. The method characterizes the compactness of rust layers rather than that of corrosion products removed from the metal surfaces, which is generally practiced in classic N2 adsorption method. Furthermore, the method can reflect the compactness of inner rust layers, to which N2 adsorption is unavailable. The method provides a new approach for the study of rust layers.

材料腐蚀与防护实验教学案例设计

针对材料类学生教学需求,以科研项目为牵引,设计了稀土合金化增强耐候钢表面锈层保护性能的实验教学案例。该实验案例以海洋大气环境下耐候钢耐蚀性能亟待提高这一实际工程问题为切入点,通过现场大气曝露腐蚀实验、实验室模拟加速腐蚀实验来评价耐候钢的耐腐蚀能力。通过扫描电镜、X射线衍射分析等物理方法和极化曲线等电化学方法,研究分析了稀土耐候钢在近海大气环境下表面锈层的形貌、物相组成、合金元素分布及其电化学腐蚀行为。利用综合实验结果分析了特定腐蚀环境下稀土耐候钢的耐蚀性能和耐蚀机理。该实验教学案例以“问题提出-材料制备-腐蚀行为分析-耐蚀性能评价”为主线,综合性强,涉及材料合金成分设计、电化学腐蚀机理、表征技术、电化学分析等众多知识点,在一定程度上实现了专业知识的系统化和一体化,对学生创新意识和研究能力的培养具有很好的推动作用。

稀土Ce对低碳微合金钢耐腐蚀性能的影响

为了提高低碳微合金钢在海洋环境中的耐腐蚀性能,采用金相显微镜、SEM、EBSD、电化学分析等测试手段研究了不同稀土Ce含量的试验钢在3.5%NaCl溶液模拟的海洋环境中的腐蚀行为。结果表明:试验钢的显微组织主要由铁素体和珠光体组成,稀土Ce可以细化晶粒,减小夹杂物的尺寸,将试验钢中Al_(2)O_(3)、MnS、Al_(2)O_(3)+MnS夹杂物改性为MnS+CeAlO_(3)、Ce_(2)O_(3)夹杂物,并且改性后的夹杂物应力明显降低,减小了微孔洞、裂纹萌生的概率。另外,稀土Ce的加入可以降低试验钢的腐蚀电流密度,提高腐蚀电压,使得腐蚀产物中γ-FeOOH的含量减少,同时α-FeOOH和Fe_(3)O_(4)含量增多,可降低反应活性,提高锈层对基体的保护作用。因此,相对于未添加稀土Ce的低碳微合金钢,添加稀土Ce的低碳微合金钢表现出更好的耐海水腐蚀性能。

EH32钢在人工海水中的流动加速腐蚀行为研究

目的 明晰流场、传质和锈层在EH32钢流动加速腐蚀过程中的协同作用机理。方法 利用射流喷射系统研究EH32钢的流动加速腐蚀行为,并基于CFD仿真模拟流场分布情况,最后通过微观形貌表征分析EH32钢的腐蚀形貌。结果 在射流喷射系统中,试样表面的流场分布不均匀,根据锈层的颜色可分为不同区域,喷嘴正对区域锈层最厚,但疏松多孔,形成凹坑,腐蚀最严重。远离喷嘴区域锈层逐渐减薄,但更致密,腐蚀形貌转变为“flow mark”和点蚀。结论 流场严重影响着腐蚀产物的分布,正应力高、剪切应力低的区域形成的锈层厚且疏松多孔,正应力低、剪切应力高的区域形成的锈层薄,但更致密。反应生成的阳极液随流体的转移过程导致了“flowmark”损伤形貌的形成,致密的锈层抑制了阳极液的转移,导致了点蚀坑的损伤形貌。锈层和阳极液的累积使得喷嘴中心区域表现为主要阳极区,腐蚀损伤最为严重,而远离中心区域由于致密的腐蚀产物抑制了传质过程,腐蚀速率较低。流场、锈层以及传质三者的协同作用决定了流动加速腐蚀行为。

车轮钢ER8在中性NaCl溶液中的电化学腐蚀行为

为研究ER8车轮钢在沿海中性氯盐环境下的腐蚀行为,通过电化学测试、腐蚀失重试验,结合扫描电镜(SEM)、X射线衍射(XRD)技术对ER8车轮钢在3种不同浓度中性NaCl溶液中的电化学腐蚀行为进行分析。极化曲线结果表明浸泡初期5.0%NaCl浓度下自腐蚀电流密度(Jcorr)最大,576 h后Jcorr在2.0%、3.5%NaCl浓度下均持续增大,腐蚀速率在2160 h时均大于0.12 mm/a。SEM结果显示腐蚀产物形貌主要为片状与团簇状结构,初期腐蚀产物形貌具有较多孔隙,难以阻碍Cl-与基体发生反应,2160 h时腐蚀产物结构更为均匀致密。XRD结果表明腐蚀产物主要由γ-FeOOH、α-FeOOH与Fe3O4组成。

460MPa级耐火耐候建筑用钢的组织和性能研究

采用低钼复合添加钛、镍、铬、铜的微合金化设计,配以合理的控轧控冷工艺,试制了低成本460 MPa级耐火耐候建筑用钢。通过周浸实验研究了实验钢在模拟工业大气环境中的耐候性能。结果表明:实验钢由粒状贝氏体、M/A岛耐火钢理想组织组成。在600℃保温时析出的大量纳米级Ti的碳氮化物,纳米析出物与位错发生交互作用,阻碍位错运动,提高了实验钢的高温力学性能。与Q345B钢相比,耐火耐候建筑用钢的耐蚀性能提升了30%以上。耐火耐候建筑用钢的锈层致密且稳定,锈层中的α-FeOOH含量较多,能有效阻止腐蚀离子接触基体。腐蚀速率及稳定锈蚀相的相对含量变化证明了耐火耐候建筑用钢锈层随时间延长变得越来越稳定,耐候性能更好。

稀土元素对耐蚀钢腐蚀性能影响的研究综述

随着工业的不断发展,世界各国对钢材质量的要求也越来越高,如何提高钢材的耐蚀性,已成为目前的研究重点。耐蚀钢因其具有较强的抗腐蚀性能,广泛应用于土木建筑、汽车制造、造船等领域,为进一步提高耐蚀钢的耐腐蚀性能,通常在钢中添加稀土元素。文中综述了稀土元素对耐蚀钢的净化作用、对钢内夹杂物的影响、对钢材腐蚀性能及锈层影响的研究进展,为促进稀土元素在钢中的应用提供理论依据。稀土元素对耐蚀钢耐蚀性影响的具体机理和稀土元素在材料工程中的可持续发展是当前研究的重点。

超高功率连续激光清洗工艺参数对Q355B钢清洗质量的影响

为了探究Q355B钢在超高功率连续激光清洗下的效果,采用超高功率光纤激光器对Q355B钢表面的铁锈等污染物进行清洗试验,研究超高功率下激光扫描速度和功率对清洗质量的影响并计算清洗效率。结果表明:清洗速度≤110 mm/s时激光对基体损伤较大,速度≥140 mm/s时仍有部分锈蚀存在于基体表面,速度在120~130 mm/s时基体未损伤并可有效去除锈蚀层;当速度恒定为120 mm/s时,功率在7 500 W以下时锈蚀未除净,功率在8 500 W以上时基材发生损伤。用SEM分析清洗前后钢材表面的微观形貌,用XRD和EDS对工件表面进行表征,随着扫描速度从100 mm/s提高到150 mm/s,功率从7 000 W提高到9 000 W,清洗后钢材表面的铁含量呈现先增加后降低的趋势,而氧含量则呈现先降低再升高的趋势。当激光功率为8 000 W,扫描速度为120 mm/s时,清洗后的工件表面铁元素的质量分数达到了峰值,约为79.25%,氧元素的质量分数则达到谷值,约为20.75%。计算得出激光清洗效率最高可达43.2 m^(2)/h。通过调节激光功率和扫描速度能在安全去除大部分Q355B钢表面污染物的同时提升材料表面的显微硬度,从而达到理想高效的激光清洗效果。

稀土Ce对X100管线钢组织及耐腐蚀性能的影响

以X100管线钢为研究对象,在实验室条件下采用真空感应炉熔炼不同稀土Ce含量的试验钢,通过扫描电子显微镜、蔡司金相显微镜、电化学工作站以及X射线衍射仪研究了Ce对X100管线钢组织及耐腐蚀性能的影响。结果表明,Ce的加入使X100钢中MnS、Mn-Si-Al-O夹杂变性成Ce_(x)O_(y)、Mn-Si-Al-O-Ce夹杂,尺寸由4μm左右增大到10μm左右。Ce对X100试验钢显微组织具有明显的细化作用,在0~0.0049%范围内,试验钢组织随着Ce含量的提高逐渐细化。Ce的加入能够提高试验钢的腐蚀电位,降低其腐蚀电流密度,在3.5%NaCl溶液浸泡28 d条件下,试验钢腐蚀电流密度由未添加Ce时的4.6347 mA/cm^(2)降低至Ce含量为0.0049%时的3.7784 mA/cm^(2),Ce含量为0.0049%时的试验钢表现出较好的耐腐蚀性能。另外,Ce的加入能够有效提高腐蚀产物中α-FeOOH和Fe_(3)O_(4)的含量,增强对钢基体的保护作用,有利于提高试验钢的耐腐蚀性能。

耐候钢表面锈层稳定化处理技术研究现状和展望

耐候钢在生产生活各领域中的使用越来越广泛,在耐候钢使用前对其进行表面锈层稳定化处理可以同时在材料延寿和美化装饰两方面增强耐候钢与其服役环境之间的相互协调。首先综述了耐候钢表面锈层稳定化处理技术的研究现状,主要包括锈层的形成、组成与结构、保护机制,特别是传统技术的缺点和新型技术的缺点;最后对此项技术未来的发展进行了展望。

一种Cr系耐候钢表面锈层稳定剂的研发

以硫酸铬作为促进剂,以聚乙烯醇缩丁醛酯作为成膜剂,制备了一种耐候钢表面锈层稳定剂。通过周期浸润腐蚀试验和电化学测试,研究了该稳定剂对耐候钢表面锈层结构、成分和耐蚀性的影响。结果表明:锈层稳定剂可避免锈液流挂现象,降低耐候钢的腐蚀速率,促使Cr元素在内锈层与基体结合处发生聚集,细化锈层晶粒,增大了锈层电阻,提高了耐候钢的耐蚀性。

921A高强碳素钢在天然流动海水中的腐蚀行为

921A碳素钢作为海洋工程用高强钢,被广泛应用于水下海洋装备的建造。921A钢在服役期间内会遭受恶劣海洋环境以及复杂流场作用,其在流动海水中的腐蚀行为是影响水下海洋装备安全运行的重要因素。为了明晰921A钢在流动海水中的腐蚀规律,利用射流喷射系统研究了海洋工程用921A高强碳素钢在不同流速(1~8 m/s)天然海水中的腐蚀行为,并结合电化学测量、微观形貌分析和计算流体力学(CFD)仿真分析了海水中流场、传质和锈层分布对921A钢腐蚀行为的交互影响机制。实验结果表明,随着海水流速从1~3 m/s升高至5~8 m/s,钢材的腐蚀损伤形貌由“流痕”转变为点蚀,海水流速增加会导致更为致密的球状锈层形成。921A钢在流动海水中的腐蚀行为受到流速、传质、壁面切应力、正应力和锈层的协同作用,锈层积累和局部腐蚀更倾向于出现在同时具有低流速、低切应力和高正应力、高传质速率特征的区域。高流速下正应力和切应力的大幅升高是导致致密锈层和点蚀形成的重要原因。921A钢的腐蚀速率在浸泡初期受活性溶解区域的发展控制,实验后期传质和锈层成为影响921A钢腐蚀速率的主要因素。在下一步工作中,将继续围绕流动海水中碳钢材料表面不同形貌锈层的形成机制与局部腐蚀发展规律开展研究。

典型耐候钢在江津大气环境中暴晒1 a的腐蚀行为

目的研究3种典型耐候钢在江津大气环境中暴晒1 a的初期腐蚀行为。方法采用户外大气挂片、腐蚀质量损失、SEM、XRD、电化学等方法,研究Q355NH、Q460FRW、Q690的腐蚀速率、锈层形貌、锈层物相和锈层电阻,并与Q345碳钢进行对比。结果耐候钢和碳钢在大气暴晒初期的腐蚀规律是一致的,Q355NH、Q460FRW、Q690和Q345碳钢的腐蚀速率分别为0.0509、0.0536、0.0478、0.055 mm/a,Q690的腐蚀速率最小,约为碳钢的87%。耐候钢和碳钢的锈层都主要由α-FeOOH、γ-FeOOH和Fe_(2)O_(3)组成,耐候钢的锈层更致密,裂纹更少。Q355NH、Q460FRW、Q690的锈层电阻值分别为821.3、1005、1080Ω·cm^(2),碳钢为101.68Ω·cm^(2),耐候钢的锈层电阻值约为碳钢的10倍。Cr和Cu元素在耐候钢的锈层中富集明显。结论耐候钢的腐蚀速率低于碳钢,3种耐候钢的耐蚀性顺序为Q690>Q355NH>Q460FRW。Cr和Cu元素在锈层中富集,使耐候钢的锈层更致密,锈层电阻值更大,对钢基体的保护性更好。

一种新开发的车体钢S500AW在户外大气环境中的腐蚀行为及寿命预测

通过大气暴晒试验结合室内加速腐蚀试验,研究了新开发的车体钢S500AW和用于对比的传统Q450NQR1钢及Q345B钢的早期腐蚀行为,采用扫描电镜(SEM)、拉曼光谱仪,分析了试验前后试样表面的腐蚀形貌和腐蚀产物成分。结果表明:在北京大气环境暴露初期,S500AW钢表面更为平整光洁,仅有少量尘埃颗粒附着物,耐蚀性更优异;腐蚀产物为Fe_(2)O_(3)和一定量的γ-FeOOH,随着腐蚀时间的延长,γ-FeOOH含量逐渐增加,钢的耐蚀性逐渐提高;以腐蚀质量损失数据为参照,建立铁路车辆车体用钢腐蚀试验方法和腐蚀寿命预测模型,通过灰色关联度分析方法,证实了周期浸润试验与户外自然环境大气暴露试验良好的相关性。