模拟铁器文物脱盐清洗前后表面锈层的分析

采用FTIR、Laser Raman和EDS对模拟铁器文物脱盐清洗前后表面锈层的结构和成分进行了研究，结果表明：在含氯离子介质中浸泡的试样腐蚀产物主要是由α、β和γ-FeOOH相及非晶δ-FeOOH相组成.经过电化学脱盐清洗后，γ-FeOOH和β-FeOOH相基本消失，腐蚀产物中主要为Fe3O4，还有少量的Fe2O3和α-FeOOH相，证实了在脱盐清洗过程中发生了羟基氧化铁向Fe3O4的转变.SEM观察结果显示针状羟基氧化铁经过脱盐清洗后变为较致密的、细小的颗粒状腐蚀产物相.EDS的分析证实了经电化学脱氯清洗后模拟铁器文物中氯离子含量大幅度减少.      

耐酸性土壤腐蚀接地网用钢研究

采用硅藻土模拟法研究了Q235,A1和A2钢在模拟酸性土壤中的腐蚀行为,对比分析了材料的腐蚀失重,利用扫描电镜(SEM)和X射线衍射(XRD)等方法研究了材料的腐蚀形貌及腐蚀产物。结果表明,在模拟酸性土壤中,Q235,A1和A2钢周期360h的腐蚀速率别为0.48,0.14和0.097mm/a。碳层分析表明,降低碳含量有助于减少钢中的微电池腐蚀;Cr的加入可以提高基体的自腐蚀电位;腐蚀后内锈层位置Cr的富集可以提高锈层的致密性,并改变点蚀的扩展方式;3种材料主要腐蚀产物均为α-FeOOH,γ-FeOOH和Fe3O4,其中A1和A2钢内锈层腐蚀产物中α-FeOOH比例增大,其α/γ-FeOOH比值约为Q235的10倍,腐蚀产物保护性更优。     

桥梁耐候钢在含Cl~-离子环境中的腐蚀行为

选择3种Ni含量为3.5%的桥梁钢,采用干湿周浸加速腐蚀实验模拟海洋大气环境下桥梁钢的耐腐蚀性能变化,并利用金相显微镜、XRD和SEM等分析了不同Mn和Cu含量桥梁耐候钢组织以及其腐蚀不同时间的腐蚀形貌和锈层特征.结果表明:桥梁耐候钢的组织由准多边形铁素体、针状铁素体和粒状贝氏体组成;随着Mn含量的增加,钢的耐蚀性能增加;Ni和Mn在锈层中均匀分布,Cu在锈层的缝隙或孔洞等缺陷处富集.锈层主要由Fe_3O_4,γFeOOH和α-FeOOH组成,腐蚀不同时间后的试样锈层组成相有所不同;γ-FeOOH和α-FeOOH与钢的腐蚀速率密切相关;增加Mn含量可以促进γ-FeOOH和α-FeOOH的生成,同时抑制γFeOOH和αFeOOH的晶粒长大.     

模拟流动海水腐蚀环境下含Cr钢与C钢的锈层研究

采用人工海水对含有相同基本成分的C钢和添加了0.95％Cr元素的Cr钢进行120h的流动冲刷腐蚀试验.利用SEM和XRD等方法研究了Cr元素对普碳钢锈层的形貌、物相构成及相对含量的影响.结果表明,经冲刷腐蚀以后,含Cr钢的腐蚀质量损失小于C钢的.对两种钢的锈层分析表明,两种实验钢的锈层均出现分层现象,普碳钢外锈层疏松多孔,而含Cr钢的外锈层呈块状,致密性明显优于碳钢,内锈层亦是如此.两种钢的外锈层均由Fe3O4、α-FeOOH和γ-FeOOH等物相构成;C钢的内锈层由Fe3O4构成,Cr元素在含Cr钢锈层中的富集没有改变外锈层的物相类型,但内锈层则由Fe3O4转变为β-FeOOH.     

耐候钢在含MgCl2介质的干湿环境下的腐蚀行为

通过以0.3%MgCl2溶液为介质的浸渍干湿循环加速腐蚀试验,研究了Corten-A耐候钢在干/湿环境下的腐蚀行为.扫描电镜(SEM)和能量色散X射线谱(EDX)观察分析了各腐蚀循环下的腐蚀形貌及Cl、Mg元素含量的变化.结果表明Corten-A钢的腐蚀失重与循环次数呈线性关系.腐蚀产物中的晶体相初期主要是β-FeOOH,后期主要是γ-FeOOH和少量的ε-Fe2O3.电化学测试表明铁锈的还原反应加速了阴极反应;锈层的电容值比较大,说明锈层的结构比较疏松,不具保护性.     

动静态服役环境下SPHC钢腐蚀行为对比

目的 研究SPHC钢在不同服役环境下腐蚀行为的差异性。方法 采用户外暴露法对SPHC钢进行长达18个月的动静态暴露试验,取样时间分别为暴露后的 3、6、9、12、18个月。通过腐蚀动力学测试、SEM(扫描电子显微镜)、XRD(X射线衍射)、电化学测试,分别评价SPHC钢在一定时长大气暴露后的平均腐蚀速率、腐蚀产物形貌、腐蚀产物成分以及锈层的耐蚀性。结果 暴露3个月时,动态暴露下SPHC钢的腐蚀速率和锈层厚度均大于静态暴露试样,在暴露6个月时被静态暴露试样反超。随后,动静态暴露下SPHC钢的腐蚀速率均缓慢下降,锈层厚度逐渐增加。动态试样表面检测出静态试样表面未检测到的β-FeOOH和SiO2,动态试样自腐蚀电流小于同期的静态试样,锈层电阻则相反。结论 由于动态暴露过程中服役环境不断变化,导致SPHC钢初期腐蚀产物中含有β-FeOOH和SiO2,增大初期试样表面的反应活性区域,加速初期腐蚀。随着暴露时间的延长,β-FeOOH和SiO2虽然使得SPHC钢难以形成如静态暴露般均匀致密的锈层,但是提高了锈层电阻,增强了SPHC钢的耐蚀性,抑制了腐蚀反应的发生。     

建筑用低合金钢在污染性大气环境中的腐蚀行为

研究了09CuPTiRE、A3、10CrNiCuP和X60钢暴露在污染性大气中的腐蚀行为。结果表明,在相同的暴露时间内,A3钢的腐蚀深度最大,X60次之,10CrNiCuP钢的腐蚀深度最小。A3和10CrNiCuP钢的腐蚀产物主要为α-FeOOH和γ-FeOOH,但含量不同。α-FeOOH含量的增加可以增强锈层的保护性,从而提高钢的耐蚀性。     

Q235碳钢在宜宾不同大气环境中的腐蚀行为

通过室外暴露试验和电化学测试,研究了电网设备主要金属材料Q235碳钢在四川宜宾地区不同大气环境中的腐蚀行为。结果表明：在四川宜宾A、B、C三个变电站环境中,Q235碳钢的平均腐蚀速率分别为19.68μm/a、41.40μm/a和28.75μm/a,其表面腐蚀产物主要由α-FeOOH、γ-FeOOH和Fe₃O₄组成,在B和C变电站环境中,Q235碳钢表面腐蚀产物中的α-FeOOH含量较高;在B变电站环境中,Q235碳钢的腐蚀电流密度最大,膜层电阻最小,说明其表面锈层对基体的保护性能较差。     

不同NaCl浓度对耐候钢腐蚀产物的影响

对Q450耐候钢在不同浓度NaCl溶液中模拟海洋大气环境进行了周期浸润试验.采用光学显微镜、扫描哇镜和X射线衍射仪对钢的腐蚀形貌、锈层截面和腐蚀产物进行了观察和分析.结果表明:随着NaCl浓度的提高,锈层变得疏松多孔;不同浓度NaCl溶液中主要腐蚀产物相同,均为γ-FeOOH及少量Fe3O4.     

Q235钢在模拟海水全浸区腐蚀行为的研究

为了研究Q235钢在海水中的耐腐蚀性及腐蚀机理,采用静态浸泡试验方法,研究了Q235钢的腐蚀速率、局部腐蚀形貌、腐蚀断面形貌,并对腐蚀层成分进行分析。结果表明:Q235钢在模拟海水全浸区的腐蚀速率先降低,然后略有升高,再略微降低,最后趋于稳定,其抗腐蚀能力较好;腐蚀先出现点蚀,最后形成连续的腐蚀层;腐蚀层分为两层:内锈层是Fe3O4、α-FeOOH、γ-FeOOH、β-FeOOH的混合物,外锈层是γ-FeOOH。     

Die Lochkorrosionsbegrenzung bei hochlegierten Sonderedelstählen und NiCrMo‐Legierungen in Chloridlösung – Einflußfaktoren und Ausmaß

Limit of pitting corrosion at high‐alloyed special steels and NiCrMo alloys in chloride solution The phenomenon of the limit of pitting corrosion in direction to positive potentials is studied by potentiokinetic polarization after a jump in the transpassive range and by potentiostatic tests at technical wrought materials and at model alloys of the systems NiCrMo and NiMo in CaCl₂ solution in the concentration range 1 to 9 mol/l chloride at pH‐values of 1 to 9 at temperatures of 30 to 110°C. Surface‐analytical investigations gives in connection with knowledges from anodic polarization studies directions to the mechanism of the limit of pitting corrosion. Ranges of the limit of pitting corrosion are obtained at materials with a Mo content above 6.5% and contents of chloride of the media above 2 mol/l chloride. Increasing temperatures, increasing contents of chloride and sulfate shift the potential of the limit of pitting corrosion being always above 0.2 V (SCE) at potentiostatic determination to noble direction. There are indications that the mechanisms of limit of pitting corrosion is resulting from an inactivation of pitting nuclei by the formation of hardly soluble molybdenum chlorides in the potential range of limit of pitting corrosion.     

Determination of the corrosion rate of powder materials by electrochemical methods

The application of polarization and impedance measurements to determine the corrosion rate of porous materials and those infiltrated with copper, produced by powder metallurgy, in neutral chloride electrolyte is examined. The determination of the corrosion rate of porous powder materials per true surface area in view of their heterogeneity is described.     

Analysis of the variability of chloride threshold values in the literature

Efforts are being devoted in standards and construction codes in order to give rules and guidelines for designing durable structures. Also efforts are focused in developing the models in a more accurate approach to the calculation of the service life of concrete structures. Service life models consider that reinforced concrete exposed to chloride polluted environments initiate corrosion when a certain amount of chlorides arrives to the rebar surface. The so‐called chloride threshold level is considered as an essential parameter for assessing the probability of reinforcement corrosion, and becomes one of the key parameters needed for service life prediction, being of interest to have testing methods and expressions to introduce in the models. Numerous studies have been carried out to establish a critical chloride level for the onset of corrosion, but a wide range of chloride threshold values has been suggested which makes not feasible to define a single value. Present paper includes the analysis of the variability of the chloride threshold values published in the literature. Data from mortar and concrete and from laboratory and field exposure are compiled and included in the analysis. The influence of the testing method used for determination and several variables are considered.     

亚共析钢 C72D2奥氏体晶粒度腐蚀剂的选用

采用直接淬硬法测定亚共析钢 C72D2的奥氏体晶粒度。选用苦味酸溶液和不同配比的三氯化铁溶液作为腐蚀剂对亚共析钢 C72D2进行腐蚀,观察并对比不同腐蚀剂的腐蚀效果。结果表明：用三氯化铁溶液（三氯化铁 5g＋浓盐酸 5滴＋水 100mL）腐蚀后的奥氏体晶界比较完整,且颜色较深,便于观察和测定,可替代苦味酸溶液进行亚共析钢 C72D2奥氏体晶界腐蚀。     

Elektrochemische Rauschmessungen zum Nachweis der Wirksamkeit von neuen Korrosionsschutzschichten auf Aluminium und Magnesium

Electrochemical noise measurements for the determination of the effectiveness of new corrosion protection layers on aluminium and magnesium The corrosion behaviour of the aluminium alloy AlMg1 and of the magnesium alloy AM60 have been investigated by electrochemical noise measurements in chloride and sulfate solutions. It should be proved, whether protecting layers based on self assembling molecules, which have been adsorbed on the samples before the electrochemical noise measurements, could inhibit pitting corrosion. The measurements do show, that several systems have an inhibitive effect, others not. Potentiostatic tests in combination with the measuements of the current noise are useful for a quick determination of the break through potential.     

Korrosionseigenschaften laserstrahlgeschweißter Aluminium- und Magnesium-Automobilwerkstoffe

Corrosion behaviour of laser beam welded aluminium and magnesium alloys in the automotive industry The pitting behaviour of unwelded and laser beam welded AlMgSi alloys and an AlMgMn alloy was investigated. Electrochemical investigations and the metallographic determination of the pit volume were used to characterize the susceptibility to pitting corrosion. Both investigation methods showed that, in the unwelded condition, the material AlMgMn was the most resistant. In the case of laser beam welded materials, the resistance to pitting corrosion is lower or also higher than that of the non-affected materials depending on the material combination selected. The material combination AlMgSi0.5/AlMgSi1 F21 proved to be the most suitable. Magnesium extruded alloys with approx. 3 to 8% Al and 0.5 to 0.8 % Zn are susceptible to filiform corrosion and pitting corrosion in aqueous chloride solutions depending on chloride concentration. The resistance of unwelded alloys increases with Al content. On welding of the alloys, the corrosion resistance is determined by the Al/Mg proportion at the surface of the non-affected material and the laser welding seam. The pits occur mainly in the heat affected zone of the welding seam. The laser beam welded material AZ61 HP was found to have the highest resistance.     

Corrosive effects of smoke with different concentrations from PVC on 304 stainless steel and 6061 aluminium alloy

Three hundred and four stainless steel and 6061 aluminium alloy samples were exposed to different concentrations of smoke generated by polyvinyl chloride in high humidity. The corrosion kinetics of 304 stainless steel and 6061 aluminium alloy under smoke were found to obey the power function and a linear rule, respectively. Pitting corrosion in smoke became increasingly obvious with exposure time. Surface morphology and chemical compositions of corrosion products were analysed by scanning electron microscope, energy dispersive spectroscopy and X-ray photoelectron spectroscopy. Possible corrosion mechanisms were proposed and compared. All the analysis helps to provide basic information for the determination of smoke damage and timely rescue after fire.     

N-methyl-2-hydroxyethylammonium oleate ionic liquid performance as corrosion inhibitor for mild steel in hydrochloric acid medium

The aim of the present study is to evaluate the performance of N-methyl-2-hydroxyethylammonium oleate ([m-2HEA][Ol]) as a corrosion inhibitor for mild steel in a 0.1-mol/L hydrochloric acid solution and also investigate the role of chloride in the inhibition mechanism. This protic ionic liquid (PIL) has formerly shown a high efficiency as a corrosion inhibitor in a neutral chloride medium. Electrochemical and weight loss measurements, surface contact angle determination, scanning electron microscopy, and Raman spectroscopy were used to understand the factors that influence the response of the studied inhibitor. Results revealed that [m-2HEA][Ol] behaves as a mixed-type adsorption inhibitor, by blocking cathodic sites and by modifying the activation energy of the anodic reaction, and it can reach up to 94–97% of inhibition efficiency. PIL adsorption was enhanced by the excess of positive charge of the mild steel. The effect of inhibitor molecule has been discussed to propose a mechanism that explains the inhibitory action of the corrosion inhibitor, pointing out the role of chloride in the inhibition mechanism.     

Determination of critical pitting temperatures for Ni?Cr?Mo alloys using electrochemical noise measurements

The determination of critical pitting temperatures (CPT) in various test solutions like ferric chloride solution according to ASTM G48 or “Green Death” solution is a common test method for the comparative assessment of the pitting corrosion resistance of highly alloyed steels and Ni? Cr? Mo alloys. In addition to the well‐known disadvantages of standard methods, like long test times, subjective examination, and large scatter, for the highest alloyed Ni? Cr? Mo alloys no stable pitting corrosion can initiate even at the highest test temperatures. This paper describes the limitations of standard test methods and shows how these problems can be solved by an alternative test solution and an adjusted test method. By capturing and examining the current noise under potentiostatic conditions during continuous heating in a 4.5 M calcium chloride solution the transition from metastable to stable pitting corrosion as a criterion for CPT can be detected in a reproducible way.     

Galvanic corrosion behavior of Ni?C filled conductive silicone rubber coupled to AZ31 magnesium alloys

The galvanic corrosion behaviors of Ni? C filled conductive silicon rubber (CSR) with different resistivity coupled to magnesium alloys were investigated in 3.5% sodium chloride solution at different temperatures. Such investigations were carried out by means of electrochemical measurement, weight‐loss determination, and surface characterization. The results indicated that the changes of CSRs' resistivity and the temperature of the electrolyte would affect the Tafel slope, cathodic corrosion current, and linear polarization resistance of the cathodic branch of the polarization curve. The lower the resistivity, the larger the average galvanic corrosion current density and the average galvanic corrosion rate of Mg alloys at the same temperature. The corrosion morphology revealed that the greater the corrosion current density, the more serious the corrosion on the surface of Mg alloys.