Influence of Ga and Bi on electrochemical performance of Al-Zn-Sn sacrificial anodes

The influence of Ga and Bi on the microstructure and electrochemical performance of Al-7Zn-0.1Sn （mass fraction,%） sacrificial anodes was investigated by means of optical microscopy （OM）,scanning electron microscopy/energy dispersive X-ray analysis （SEM/EDAX） and electrochemical measurements.It was found that the coarse dendrites structure transformed into the equiaxed grains as well as a small amount of dendrite grains after adding Ga and Bi into Al-Zn-Sn alloys.A high current efficiency of 97% and even corrosion morphology were obtained for Al-7Zn-0.1Sn-0.015Ga-0.1Bi alloy.The results indicate that the proper amount of Ga and Bi is effective on improving the microstructure and electrochemical performance of Al-Zn-Sn alloy.

Influence of Mg and Ti on the microstructure and electrochemical performance of aluminum alloy sacrificial anodes

The experiments focused on the influence of magnesium and titanium as additional alloying elements on the microstructure and electro-chemical behavior of Al-Zn-In sacrificial anodes. The electrochemical behavior of the aluminum sacrificial anode with 3 wt.% sodium chloride solution was studied by electrochemical impedance spectroscopy (EIS) tests. It was found that a microstructure with few precipitates and refined grains could be achieved by adding 1 wt.% Mg and 0.05 wt.% Ti to the Al-Zn-In alloy,resulting...

Effect of Zn/Mg ratio on cathodic protection of carbon steel using Al-Zn-Mg sacrificial anodes

Al-Zn-Mg alloys with different Zn/Mg mass ratios were evaluated as sacrificial anodes for cathodic protection of carbon steel in 3.5 wt.%Na Cl solution.The anodes were fabricated from pure Al,Zn and Mg metals using casting technique.Optical microscopy,SEM-EDS,XRD and electrochemical techniques were used.The results indicated that with decreasing Zn/Mg mass ratio,the grain size ofα(Al)and the particle size of the precipitates decreased while the volume fraction of the precipitates increased.The anode with Zn/Mg mass ratio>4.0 exhibited the lowest corrosion rate,while the anode with Zn/Mg mass ratio<0.62 gave the highest corrosion rate and provided the highest cathodic protection efficiency for carbon steel(AISI 1018).Furthermore,the results showed that the anode with Zn/Mg mass ratio<0.62 exhibited a porous corrosion product compared to the other anodes.

Effect of Oxide Inclusions on Electrochemical Properties of Aluminium Sacrificial Anodes

Oxide films are incorporated into melts by an entrainment process, and are expected to be present in most metals, but particularly cast Al alloys. The oxides are necessarily present as folded-over double films （bifilms） that are effectively cracks. Their effect on the electrochemical behaviour of cast Al-SZn-0.021n sacrificial anodes was studied in 3 wt pct sodium chloride solution using the NACE efficiency evaluation. Three methods were employed to entrain progressive amounts of oxide in the alloy, including the addition of Al-Zn-ln maching chips to the charge, increasing the pouring height, and agitating the melt. The introduction of oxide bifilms in the cast alloy resulted in the deterioration of the electrochemical properties of the sacrificial anodes, such as current capacity and anode efficiency, and introduced increasing variability in these properties. The results suggest that corrosion behaviour is strongly related to the presence of bifilms suspended in the liquid alloy because bifilms provide crack paths allowing the corrodant to penetrate deeply into the metal matrix, and simultaneously provide localized galvanic cells because of the precipitation of Fe rich intermetallic compounds on their outer surfaces.

Effects of strain-induced melt activation treatment on the microstructure and properties of Zn sacrificial anodes

The microstructural properties and electrochemical performance of zinc(Zn)sacrificial anodes during strain-induced melt activation(SIMA)were investigated in this study.The samples were subjected to a compressive ratio of 20%-50% at various temperatures(425-435℃)and durations(5-30 min).Short-term electrochemical tests(anode tests)based on DNV-RP-B401 and potentiodynamic polarization tests were performed in 3.5wt%NaCl solution to evaluate the electrochemical efficiency and corrosion behavior of the samples,respectively.The electrochemical test results for the optimum sample confirmed that the corrosion current density declined by 90% and the anode efficiency slightly decreased relative to that of the raw sample.Energy-dispersive X-ray spectroscopy,scanning electron microscopy,metallographic images,and microhardness profiles showed the accumulation of alloying elements on the boundary and the conversion of uniform corrosion into localized corrosion,hence the decrease of the Zn sacrificial anode’s efficiency after the SIMA process.

Effect of Sacrificial Anode Protection for Steel Pipe Piles at Dandong Port

The sacrificial anode protection system for the steel pipe piles of the 3rd berth of Dandong; wharf at Dandong port has operated for eight years. In this paper, the program design and the protection effect of the sacrificial anode protection system are presented. The results of various inspections show that the piles are protected very satisfactorily.

Sacrificial Anode Stability and Polarization Potential Variation in a Ternary Al-xZn-xMg Alloy in a Seawater-Marine Environment

In this paper, the effects of zinc （Zn） and magnesium （Mg） addition on the performance of an aluminum-based sacrificial anode in seawater were investigated using a potential measurement method. Anodic efficiency, protection efficiency, and polarized potential were the parameters used. The percentages of Zn and Mg in the anodes were varied from 2% to 8% Zn and 1% to 4% Mg. The alloys produced were tested as sacrificial anodes for the protection of mild steel in seawater at room temperature. Current efficiency as high as 88.36% was obtained in alloys containing 6% Zn and 1% Mg. The polarization potentials obtained for the coupled （steel/Al-based alloys） are as given in the Pourbaix diagrams, with steel lying within the immunity region/cathodic region and the sacrificial anodes within the anodic region. The protection offered by the sacrificial anodes to the steel after the 7th and 8th week was measured and protection efficiency values as high as 99.66% and 99.47% were achieved for the A1-6%Zn-l%Mg cast anode. The microstructures of the cast anodes comprise of intermetallic structures of hexagonal Mg3Zn2 and body-centered cubic A12Mg3Zn3. These are probably responsible for the breakdown of the passive alumina film, thus enhancing the anode efficiency.

Effects of Zinc Addition on the Performance of Aluminium as Sacrificial Anode in Seawater

In this work, the effect of zinc addition on the performance of aluminium-based sacrificial anode in seawater was investigated. The parameters used in assessing the performance of the cast anodes are anodic efficiency, protection efficiency and polarized potential. The percentages of Zn in the anodes were varied from 1 to 8%Zn. The alloys produced were tested as sacrificial anode for the protection of mild steel in seawater at room temperature. Current efficiency as high as 86.69% was achieved at 6%Zn in the alloys. The polarized potential obtained for the couples(steel/Al based alloys) are as given in the pourbaix diagrams with the steel lying within the immunity region/cathodic region ( S-0.5V SHE) and the sacrificial anodes within the anodic region. The protection offered by the sacrificial anodes to the steel after the 7th and 8th week were measured. Protection efficiency values as high as 99.26% and 99.13% were achieved after the 7th and 8th with Al-6%Zn. The microstructure showed the intermetallic structures of β-phase which breakdown the alumina passive film and thus enhancing the anode efficiency.

Environmental Impact Assessment of Sacrificial Anode Method in Taiwan Strait

Taiwan Strait is one of the potential wind farm in the world. Cooperate with the development of national policies, thousands of offshore wind turbines will be installed in Taiwan Strait. In order to enable offshore wind turbine foundation to be erected in the ocean for a long time, the offshore structure facilities are protected by sacrificial anode or impressed current of today. This study utilized the MIKE21 numerical model, combined with ocean parameters such as sea waves and tidal current to simulate the change of the diffusion concentration and diffusion range of the materials released by the aluminum sacrificial anode blocks by the Changhua offshore wind farm located on Taiwan Strait in winter and summer, thus to evaluate the impact on the marine environment.

Performance of Sacrificial Anodes in Reinforced Concrete

The electrochemical performance of the anodes was measured in the reinforced concrete test block in artificial sea water. Their chemical composition,metallographic structure and surface morphology were analyzed. It was found that concrete mix proportion and the covering layer thickness had an impact on the performance of sacrificial anodes. The thermal-sprayed zinc alloy anodes had a more negative corrosion potential and larger galvanic current than metallurgy ones in the same conditions. They had similar chemical composition. But metallographic structure showed that the structure of thermal-sprayed zinc alloy anodes was a loose porous. This structure had the catalytic effect on the andes electrochemical reactions and made the anodes the electrochemical exchange current density increase and the corrosion potential move to negative direction.

Gas free oxidation of NaCN for presodiating and stabilizing the anodic host of sodium-ion capacitors

Sodium-ion capacitors(NICs)trigger considerable attention due to their higher specific energy than electrical double-layer capacitors(EDLCs)at comparable specific power.However,the presodiation process of the anodic host is extremely crucial for the construction of high-performance NICs.Herein,a positive EDL electrode containing activated carbon(AC)mixed with sodium cyanide(NaCN)as a sacrificial material was electrochemically oxidized to presodiate a Sn_(4)P_(3) anodic host buffered by hard carbon(HC).The oxidation of CN-occurred ca.2.9 V vs.Na/Na+and finished by a short region of linearly increasing potential with a total capacity close to the theoretical value of 547 mAh g^(-1).The operando electrochemical mass spectrometry(EMS)analysis of the atmosphere in the cell together with the internal pressure measurements realized during the galvanostatic oxidation of a YP80F-NaCN electrode demonstrate that the process occurs without any gas evolution.A precursor cell of an NIC was constructed in a pouch with YP80FNaCN and HC/Sn_(4)P_(3) electrodes.After the oxidative sodium transfer from NaCN to HC/Sn_(4)P_(3),the realized YP80F//Nax(HC/Sn_(4)P_(3))NIC demonstrated a discharge capacitance retention higher than 80%for 8900 cycles in the voltage range from 2.0 to 3.8 V.The infrared analysis of the anode obtained by the herein described transfer process detected polycyanogen,which stabilizes the electrode structure during cycling,and thereof is at the origin of the enhanced life span of the NIC.

碳化及氯盐侵蚀条件下锌牺牲阳极对钢筋保护行为研究

采用水泥基材料包覆的金属锌作为牺牲阳极,通过混凝土模拟孔溶液模拟碳化及氯离子侵蚀环境,研究牺牲阳极材料对钢筋的保护作用。电化学测试结果表明,当Q235钢片和纯锌片形成电偶对时,Q235钢在质量分数为1.5%的氯化钠溶液中易发生锈蚀,而在溶液中添加适量的碱(LiOH)以及卤素碱金属化合物(LiBr)能够激发金属锌持续溶解,持续提供牺牲阳极保护,有效抑制钢片的腐蚀。结合XRD测试结果可知:LiOH可以维持锌的溶解,并且与锌片反应生成锌的氢氧化物;卤素碱金属化合物可以诱发金属锌的腐蚀。相比于卤素碱金属化合物,加入高浓度LiOH对钢筋的阻锈效果更好。本研究有助于完善牺牲阳极材料的激发技术,提升牺牲阳极技术对钢筋的保护作用。

基于COMSOL的导管架平台阴极保护研究

牺牲阳极阴极保护技术是防止海洋平台腐蚀的一种可靠手段。该文以导管架平台为研究对象,选取DNV设计准则,确定牺牲阳极的数量及相关布置,设计一套可靠的牺牲阳极阴极保护系统方案。借助数值仿真技术,通过研究导管架表面电位分布及腐蚀速率的变化来探究服役期间导管架平台阴极保护效果随阳极溶解的变化。

新型平衡舵阴极保护设计与保护效果评价

目的 针对新型平衡舵结构的电偶腐蚀薄弱区域,设计并优化牺牲阳极保护系统,并对保护效果进行评价。方法 基于边界元法,开展新型平衡舵电偶腐蚀仿真研究,分析电偶腐蚀薄弱区域。针对腐蚀薄弱区域,采用经验法设计牺牲阳极保护系统,开展服役初期和服役3 a后阴极保护效果仿真。从涂层破损率和阳极数量对阴极保护效果的影响出发,优化阴极保护系统。开展物理模型试验,对优化后阴极保护系统的保护效果进行评价。结果 电偶腐蚀主要发生在壳体和底座等支撑材料处,必须采取严格的防腐措施。采用经验法设计的牺牲阳极保护系统在服役初期可以使平衡舵保护电位均负于–800m V,处于良好的阴极保护状态。随着阳极的消耗,服役3 a后,阴极保护系统无法为平衡舵提供有效保护。涂层破损率的增加和阳极数量的减少,都会使平衡舵阴极保护电位正移。通过物理模型试验验证了优化后阴极保护模型的可靠性,对比试验结果,模型的预测误差在5%以内。结论 优化后的阴极保护方案为涂层+8块牺牲阳极,可以在服役3 a涂层破损率达20%的严苛工况下,为平衡舵提供有效阴极保护。优化后的阴极保护系统,铝阳极用量减少30%,有助于节省船舶动力。

Effect of lanthanum addition on microstructure and corrosion behavior of Al-Sn-Bi anodes

Novel Al-Sn-Bi anodes with and without lanthanum （La） were prepared.To evaluate the corrosion properties of the anodes,constant current and dynamic loop tests were carried out to determine its efficiency and corrosion rate.Optical microscopy （OM）,transmission electron microscopy （TEM） and energy spectrum analysis techniques were used to examine and analyze microstructure and corrosion behavior of the specimens.The result showed that the Al-Sn-Bi anodes with La additions revealed higher current efficiency and anticorrosion in artificial environment.Segregation phase of anodes with La additions got more homogenous than that without La additions.Its grains were fined and the amount of segregation Fe-phase was reduced.

Optimization of Manganese and Magnesium Contents in As-cast Aluminum-Zinc-Indium Alloy as Sacrificial Anode

In this study, effects of manganese and magnesium content on the electrochemical properties of Al-Zn-ln sacrificial anode were studied in 0.5 mol/L NaCl solution （pH=5）. The aluminum base alloy with different amounts of Mn and Mg were melted at 750℃, then casted at molds at 25℃. Corrosion experiments were mounted to determine the optimal effect of Mn and Mg on the efficiencies of the aluminum alloy anodes. The corroded and unexposed sample surfaces were subjected to microstructure characterization by optical and scanning electron microscopy. AI-Zn-ln alloy doped with 0%, 0.01%, 0.05%.0.2% and 0.3% by weights of Mn and 0%, 0.5%, 1.0%, 1.5%, 2.0%, 2.5% and 3.0% by weights of Mg were prepared to determine the effect of Mn and Mg on anode efficiency in the environment. The different microstructures of the evolved AI- Zn-ln-Mg-Mn alloy were correlated with the anode efficiencies. The Al-5.0%Zn-2.0%Mg-0.15%Mn-0.02%ln gave the best anode efficiency （about 83%）. The microstructures of the corroded surface of the optimized alloy revealed decreased distribution of the pockets of localized attacks which are characteristics of pitting （or crevice） corrosion.

Influence of yttrium addition on properties of Mg-based sacrificial anode

To improve lower current efficiency of Mg-based sacrificial anode,a Mg-based sacrificial anode material with yttrium addition was investigated.Its electrochemical properties were evaluated by the galvanostatic method,and its microstructure and constitution were characterized by metallurgical microscope and X-ray diffraction.The results showed that,the addition of yttrium refined dentrite grains,maximized current efficiency,and minimized potential of magnesium sacrificial anode.When 0.1% yttrium was doped,the anode showed the highest current efficiency,62.5%,which improved its current efficiency by 14%.

哈利波特中国行主题创新科普实验——武汉站:化学魔法与现实世界的交融

本科普实验以青少年喜爱的魔幻文学人物哈利波特中国行为主题,以他的武汉之旅展开行程,用实验呈现博物馆的青铜器修复技术,“知音号”游轮的牺牲阳极法防腐技术,武汉长江大桥的水泥固化和桥头堡及桥墩的3D打印技术,黄鹤楼绘制的碳量子点制备技术;在潜移默化中传播化学知识。

某深水海底管道牺牲阳极消耗异常的原因

近年来,南海东部海域出现了海底管道牺牲阳极加速消耗的情况,深水阴极保护系统面临失效风险。为了探究海底管道牺牲阳极消耗异常的原因,对管道开展了设计资料调研与室内评价试验,其中室内评价试验包括管线钢的保护电流密度需求量试验、阳极电化学性能评价试验和海管与水下系统结构电连接的室内缩比试验,着重探究了温度以及海管与水下结构物电连接对牺牲阳极消耗的影响。结果表明:温度不是引起海底管道阳极消耗异常的主要因素,而当管道与阴极保护状态较差的水下结构物电连接时,靠近水下结构物的海管牺牲阳极输出电流增大,阳极使用寿命将大幅降低,这是造成牺牲阳极加速消耗的主要原因。

活化元素对锌合金牺牲阳极电化学性能的影响

目的 满足深潜装备用高强钢材料阴极保护需求,探明活化元素对锌合金牺牲阳极电化学性能的影响规律。方法 采用合金化设计方法,控制活化元素,制备新型锌合金牺牲阳极。通过常规电化学性能试验、电化学测试、扫描开尔文探针测试数据及微观形貌表征结果,综合分析活化元素对锌合金牺牲阳极组织和综合性能的影响,探明低驱动电位锌合金牺牲阳极性能的变化规律。结果 添加Ga、Mn、Sn和Cd活化元素的牺牲阳极,表面溶解形貌相对均匀,阳极电位发生不同程度的正移,用于阴极保护时,驱动电位得到降低,其工作电位基本处于–1.02~–0.8 V(vs. Ag/AgCl),牺牲试样呈现表面溶解活性降低、溶解速率变慢的趋势。结论 通过添加各类活化元素,均使锌合金牺牲阳极性能得到不同程度的优化改善。Cd元素可增大阳极试样表面的杂乱度,随Sn、Mn含量的增加,牺牲阳极试样的晶粒尺寸得到一定细化。其中,Zn-0.5Mn系列牺牲阳极较满足高强钢阴极保护的需求,工作电位为–0.95~–0.84V(vs.Ag/AgCl),表面活性位点分布均匀,可进一步开发适用于高强钢结构材料阴极保护的新型牺牲阳极。