Electrochemical investigations on corrosion protection oils

Tribologically affected surfaces of high‐strength steels often only may be protected against corrosion by the use of specific protecting oils. The protective effectiveness of these products is usually assessed by neutral salt spray test during qualification. As this test method takes a long time and because the reproducibility is poor a new test method was developed based on electrochemistry. It could be shown that a distinction was possible between well and nonprotecting oils based on current density curves and electrochemical impedance spectroscopy.     

合金元素Ga对Al-Zn-Bi系阳极材料腐蚀机理的影响

采用恒电流法测定了添加Ga元素前后的Al-Zn-Bi系合金在人造海水中的开路电位、工作电位和电流效率,观察了该试验过程后合金的表面腐蚀形貌;利用极化曲线和电化学阻抗谱研究了该阳极合金在3.5%NaCl溶液中腐蚀过程的演变规律。结果表明：Ga能使Al-Zn-Bi系合金开路电位负移,工作电位稳定,电流效率升高,腐蚀形貌更加均匀;Ga可均匀固溶于铝合金中,并与回沉积的阳离子形成Ga基汞齐,使得阳极合金的活化控制步骤由第二相粒子优先溶解-脱落机理转变为金属阳离子的溶解-再沉积机理,促进阳极合金的均匀溶解,从而提高其综合电化学性能;等效电路RL（Cs（CpRp）（Q1Rd1）（LRa））和RL（Cs（CpRp）（Q1Rd1）（LRa）（Q2Rd2））能较好地表征两种合金的腐蚀行为和活化机理。     

Effect of the T6 heat treatment on corrosion behavior of additive manufactured and gravity cast AlSi10Mg alloy

This study investigates the corrosion behavior of AlSi10Mg alloy produced by additive manufacturing and gravity casting before and after T6 heat treatment. Electrochemical tests showed that the additive manufactured material in as‐produced condition exhibits high corrosion resistance, due to the very fine microstructure, while immersion test allowed to identify an exfoliation‐like corrosion phenomenon, which caused a significant mass loss. In this case, T6 heat treatment was beneficial for corrosion resistance since the related change in microstructure led to a less detrimental corrosion mechanism. Therefore, the T6 heat treatment resulted necessary to use additive manufactured AlSi10Mg components in aggressive chloride‐bearing environments.     

稀土Ce对7A04铝合金耐腐蚀性能的影响

目的提高7A04铝合金的耐腐蚀性能。方法采用周期浸润腐蚀试验模拟海洋大气环境,研究了不同稀土Ce含量的7A04铝合金的腐蚀行为及规律。通过金相显微镜和扫描电子显微镜,观察了不同试样的组织和夹杂物形貌。采用失重法和电化学阻抗技术,分析了试样的腐蚀动力学规律及电化学行为特性。结果在Ce质量分数分别为0%、0.39%和0.81%的7A04铝合金中,稀土Ce的加入量为0.39%时,其晶粒最细小,第二相与夹杂最少且分布最均匀,合金的基体组织得到了改善。稀土7A04铝合金的腐蚀失重明显低于不含稀土Ce的7A04铝合金,且锈层电阻升高,其中含0.39%稀土Ce的7A04铝合金的锈层电阻最高。结论三种7A04铝合金均发生了明显的局部腐蚀,主要为点蚀。稀土Ce的加入,改变了非稀土铝合金中的T相和S相,生成了新的细小的块状金属间化合物,改善了组织的均匀性,提高了其腐蚀锈层电阻,增加了锈层对基体的保护能力,使铝合金耐海洋大气腐蚀性能提高。在三种稀土Ce含量的铝合金中,含0.39%稀土Ce的7A04铝合金的耐蚀性最佳。     

Effect of Schiff base as corrosion inhibitor on AZ31 magnesium alloy in hydrochloric acid solution

Schiff base derived from the condensation reaction of analar grade 1-amino-2-naphthol 4-sulphonic acid with cinnamaldehyde was prepared under microwave condition. The Schiff base was analysed by infrared spectroscopy. This Schiff base as a corrosion inhibitor of AZ31 magnesium alloy in 0.05 mol/L HCl solution was studied. The inhibition effect of the Schiff base compound (4Z)-4-(3-phenyl allylidene amino)-3-hydroxy naphthalene-1-sulfonic acid (AC) on AZ31 magnesium alloy corrosion was studied using mass loss, potentiodynamic polarization technique, electrochemical impedance spectroscopy methods. The potentiodynamic polarization curve shows that Schiff base AC inhibits both anodic and cathodic reactions at all concentration, which indicates it is a mixed type inhibitor. EIS results indicate that as the additive concentration is increased, the polarization resistance increases whereas double-layer capacitance decreases. The adsorption of AC on the AZ31 magnesium alloy surface in 0.05 mol/L HCl obeys the Langmuir adsorption isotherm.     

X90管线钢焊接接头耐腐蚀性能研究

采用金属浸泡腐蚀试验、电化学腐蚀试验研究不同浓度或pH的HCl、NaOH、NaCl溶液对X90管线钢焊接接头(SMAW、GMAW、SAW)耐腐蚀性能的影响。结果表明:三种焊接接头的腐蚀速率随溶液浓度增加而增加,其中焊接接头对碱性环境耐蚀性较好,耐酸、盐类腐蚀性能较差,在较低浓度或pH下腐蚀接近轻度级别,SMAW焊接接头在pH=1的HCl溶液和5%的NaCl溶液中腐蚀达到重度级别。电化学腐蚀试验表明,SMAW试样自腐蚀电流最高,阻抗最低,三种焊接接头腐蚀均为重度级别,因此在强电解质溶液中建议采取保护措施。     

The corrosion characteristics and solderability of immersion tin coatings on copper

Immersion tin is widely used as a lead free surface finish in the printed circuit board technology. Tin prevents the underlying copper from corrosion and preserves its solderability during a long storage and lead‐free assembly processes. Investigated immersion tin coatings were deposited on copper foil from thiourea‐type baths with hydrochloric acid addition (SnHCl coatings) or methanesulfonic acid addition (SnMSA coatings). Obtained coatings were investigated in the as deposited state and after aging (4 h at 155 °C, in air). The scanning electron microscopy studies revealed differences in structure of tin samples deposited from different baths. Results of polarization and impedance investigations indicated that as deposited SnHCl coatings had better corrosion resistance in 0.5 M NaCl solution than SnMSA coatings. The aging resulted in the improvement of the corrosion resistance of thinner coatings (0.2 and 0.5 µm thick SnHCl and 0.3 µm thick SnMSA), which were thoroughly converted into Sn–Cu intermetallic (IMC) phases. In contrary, thicker coatings exhibited some worsening of the corrosion resistance upon aging. The solderability of all as‐deposited tin coatings was acceptable, but decreased after aging, especially for thinner coatings, showing the through conversion into Sn–Cu IMC phases.     

Comparison of the in vitro corrosion behavior of biodegradable pure Zn in SBF, 0.9% NaCl,and DMEM

Zn-based alloys are considered to be the new biodegradable implant materials due to their suitable degradation rate and good biocompatibility. The biocorrosion behavior of pure Zn in 0.9% NaCl, simulated body fluid, and Dulbecco's modified Eagle's medium (DMEM) was investigated by electrochemical and immersion tests. These tests revealed that pure Zn has the lowest corrosion rate in DMEM and the highest in 0.9% NaCl. Aggressive Cl⁻ has an important effect on the corrosion process. Buffering agents, amino acids, and glucose have a close connection with corrosion resistance. Among the three solutions, DMEM with a similar ion concentration and necessary nutriments is recommended as the more suitable choice for estimating biodegradable alloys' in vitro degradation.     

Mechanistic study of stress corrosion cracking of carbon steel in ethanol

Mechanistic study of stress corrosion cracking of carbon steel in fuel‐grade ethanol was made using slow strain rate testing and constant tensile load testing at yield strength stress level of the steels. Characterization of the fracture surface was made using SEM and SEM–EDS. Selective dissolution of ferrite from pearlite phase was observed. Crack initiation took place preferably from pearlite phase. Corroded zones consisting of crystallographic pits were found from fracture surfaces.     

Influence of a biopolymer admixture on corrosion behaviour of steel rebars in concrete

Among the multitude of concrete structure pathologies, corrosion of rebars is one of the most important problems of concrete durability. In the context of sustainable development, it appears of primary importance to develop new means to protect the rebars against corrosion. This study aims to develop a new eco‐friendly and corrosion‐inhibiting admixture based on EPS 180 exopolysaccharides, biopolymers used in coatings already studied for the corrosion inhibition on steel in seawater. C15 rebars embedded in CEMI and CEMV cement paste containing EPS 180 were immersed in natural seawater and their electrochemical behaviour was studied using open circuit potential measurements and electrochemical impedance spectroscopy. These tests highlight the decrease of the cathodic reaction kinetics due to the EPS 180 action at the rebars surface, and the absence of effect on the passive layer. Capillary imbibition tests carried out on cement paste and mortars showed that although limiting the imbibition kinetics for cement pastes, the EPS 180 did not influence the water imbibition of mortars. Tests comparing capillary imbibition of soaked cement pastes and mortars with EPS 180 solution and the same samples containing the EPS 180 admixture highlight that the corrosion inhibition induced by EPS 180 admixture is more due to the modification of the cement – rebars interface than to the clogging of the cement porous network.     

Cl-浓度对2A12铝合金电化学行为的影响

通过干湿周浸试验、扫描电镜观察和电化学阻抗谱(EIS)测试,研究了2A12铝合金在不同质量浓度NaCl溶液中干湿周浸48 h和480 h后带锈样的电化学行为与规律.试验结果表明,干湿周浸48 h后,低浓度NaCl溶液中2A12铝合金的腐蚀过程主要受电荷转移电阻控制;随浓度增加,其电化学特征转变为受电荷转移电阻和Warb...     

Application of LPR and EIS techniques for on-site corrosion monitoring at the geothermal plant in Central Poland

Corrosion monitoring station was installed at ‘Geotermia Mazowiecka’ geothermal plant in Poland. Linear polarisation resistance and electrochemical impedance spectroscopy techniques were applied to estimate the corrosion rate and the surface changes of K55 carbon steel, L80-13CR and 316 stainless steels directly in the geothermal water flux. The enhanced corrosion of K55 carbon steel and corrosion rate of L80-13CR and 316 stainless steels was observed. The formation of biofilm increased the resistivity of the surface.     

热镀锌钢表面乙烯基三乙氧基硅烷膜的腐蚀电化学行为

采用开路电位(OCP)、交流阻抗(EIS)和动电位极化法对热镀锌钢表面乙烯基三乙氧基硅烷膜腐蚀电化学行为进行了研究。结果表明,在3.5%NaCl溶液中,涂覆硅烷膜层的热镀锌钢与空白热镀锌钢相比,其低频阻抗值提高至少2个数量级,同时腐蚀电流密度减小1个数量级以上,乙烯基三乙氧基硅烷膜防腐蚀效果良好。     

Hg和Ga元素对Mg阳极材料组织和电化学腐蚀性能的影响(英文)

采用动电位极化、恒电流和交流阻抗测试方法研究了Hg和Ga元素对Mg2%Hg,Mg2%Ga和Mg2%Hg2%Ga合金电化学腐蚀性能的影响,并用扫描电镜、X射线衍射和能谱分析了上述合金的显微组织和腐蚀表面形貌。结果表明:Mg2%Ga合金是固溶体,Mg-2%Hg和Mg-2%Hg2%Ga合金的晶界有白色第二相。Mg-2%Ga合金的平均电位为1.48V,腐蚀电流密度为0.15mA/cm2,电化学活性差,耐腐蚀性能好。Mg-2%Hg-2%Ga合金的平均电位1.848V,腐蚀电流密度为2.136mA/cm2,电化学活性好,耐腐蚀性能差。MgHgGa合金的活化机制是Hg和Ga原子的溶解沉积。     

Effect of Ti3SiC2 content on the corrosion behavior of Al/Ti3SiC2 composite coatings

The purpose of this study was to investigate the electrochemical corrosion properties of flame-sprayed Al and Al/(5, 10, 15)% Ti₃SiC₂ coatings in a 3.5% NaCl solution. Scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDS) were used for analyzing the microstructural characteristics of the coatings. For examining the corrosion behavior of the coatings, a potentiodynamic polarization test and electrochemical impedance spectroscopy (EIS) were used. After the potentiodynamic polarization test, the SEM micrograph of coatings indicated that Ti₃SiC₂ particles played a significant role in pitting corrosion. The results of potentiodynamic polarization tests revealed that Al/Ti₃SiC₂ coating is nobler than that of the pure aluminum coating. On the contrary, the addition of Ti₃SiC₂ particles reduced the process of thickening the passive layer. The results of the EIS tests demonstrated that the presence of Ti₃SiC₂ particles significantly enhances the corrosion resistance of the coatings.     

稀土对超高强度钢耐海洋大气腐蚀性能的影响

目的提高超高强度钢耐海洋大气腐蚀的性能。方法采用周期浸润腐蚀试验箱模拟一般条件下海洋大气腐蚀试验,通过金相显微镜和扫描电子显微镜观察低合金超高强度钢的组织和夹杂物的形貌,采用失重法和电化学阻抗技术分析腐蚀动力学规律及电化学行为规律。结果稀土在低合金超高强度钢中具有细化组织和变质夹杂物的作用,稀土增强了锈层的致密性,使得低合金超高强度钢的耐蚀性能显著提高,且随着稀土含量的增加,锈层电阻值逐渐增大,即稀土提高了锈层对基体的保护能力。结论在低合金超高强度钢中添加稀土能够细化组织、变质夹杂物。稀土低合金超高强度钢的夹杂物主要为球形稀土复合氧硫化物。稀土质量分数为0.08%的低合金超高强度钢的耐腐蚀性能最好。     

Electrochemical techniques for monitoring stress corrosion cracking of Type 40Cr steel in acidified chloride solution

Electrochemical impedance spectroscopy （EIS） and electrochemical noise （EN） techniques were used to detect stress corrosion cracking （SCC） on 40Cr steel specimens exposed to the acidified chloride solution at ambient. To test these two techniques, slow strain rate tensile （SSRT） tests were performed with 40Cr specimen in the identical corrosive solution at room temperature. In impedance measurements, phase shifts in frequency range from 1 to 1 000 Hz show a clear difference between the stressed and non-stressed specimens, suggesting that stress corrosion cracks are detected by the impedance measurements. EN signals in the process of SCC were recorded and then analyzed by standard deviation （STD）. On the other hand, the mechanical properties, such as maximum tensile strength （MTS） and fracture strain （FS） measured by the SSRT, decrease significantly when the specimens are exposed to the corrosive solution relative to that in an inert medium. The SSRT results are consistent with fractography of the tested specimens by scanning electron microscopy （SEM）. Analysis of the fracture surface clearly shows intergranular attack, suggesting that stress corrosion cracks are formed.