环氧铝粉涂层和氟碳涂层耐蚀性能的比较

采用电化学阻抗谱技术(EIS)研究了环氧铝粉涂层和FEVE氟碳涂层/碳钢体系在天然海水介质中的电化学腐蚀行为,通过对两涂层的涂层电容分析及腐蚀后表面形貌的观察,评价了两种有机涂层的防腐蚀性能。结果表明,随着浸泡时间的延长,两种有机涂层体系的保护作用都有所降低。环氧铝粉涂层在浸泡初期呈现单容抗弧特征,浸泡57天时出现了双容抗弧。氟碳涂层在浸泡周期内EIS曲线均呈现单容抗弧特征,浸泡110天时低频阻抗模值仍高于108Ω.cm2。在整个浸泡周期内,氟碳涂层的涂层电容基本维持在1.6×10-10～1.8×10-10 F.cm-2,约为环氧铝粉涂层电容的1/20,表现出低渗水性。     

氯离子环境下混凝土钢筋的电化学阻抗谱特征

用电化学阻抗谱(EIS)方法研究了混凝土钢筋浸泡在氯离子溶液中的阻抗谱特征,研究结果表明:浸泡初期,钢筋电化学阻抗谱为一半径很大的容抗弧,钢筋处于钝化状态;随着腐蚀的发展,钢筋的阻抗谱表现为双容抗弧,钢筋表面的钝化膜已破裂,钢筋发生了孔蚀,其腐蚀过程受电荷传递过程控制;在浸泡后期,阻抗谱低频段出现了Warburg阻抗,...     

Zr-4合金表面氧化膜的电化学阻抗谱特征

电化学阻抗谱是分析锆合金表面氧化膜结构及其演化行为的有效方法。利用10%HCl溶液研究了锆合金在400 ℃, 10.3 MPa过热蒸汽中腐蚀后的表面氧化膜电化学阻抗行为。结果表明：锆合金过热蒸汽腐蚀初期表面氧化膜的阻抗谱为单一容抗弧，随着腐蚀进行而演变为双容抗弧。氧化膜表现为双层膜结构特征。氧化膜阻挡作用的降低是锆合金过热蒸汽腐蚀发生转折的一个原因。锆合金中第二相粒子对氧化膜阻抗谱及合金耐蚀性有较大影响     

温度对904L不锈钢耐点蚀性能的影响

采用FeCl3溶液浸泡试验、动电位极化、电化学阻抗谱及体式显微镜研究了904L超级奥氏体不锈钢在不同温度下的点蚀行为。结果表明:溶液温度为25℃时,904L不锈钢具有优异的耐点蚀性能,随着溶液温度的升高,其耐点蚀性能下降,在65℃FeCl3溶液中基体表面产生严重的点蚀坑。在不同温度模拟海水溶液中的电化学测试结果同样表明:随着试验温度的提高,自腐蚀电流密度增大,点蚀电位下降,点蚀敏感性提高;EIS均为单一的容抗弧,温度升高,容抗弧半径减小,材料腐蚀速率增大,耐蚀性降低。     

304L不锈钢在硼酸水溶液中的腐蚀行为

采用动电位极化曲线、电化学阻抗谱、扫描电镜和能谱分析方法研究了304L不锈钢在硼酸水溶液中的腐蚀行为。结果表明,304L不锈钢的自腐蚀电位和腐蚀电流密度随着硼酸水溶液温度的升高而增大;不同温度下的电化学阻抗谱呈单容抗弧,表现为一个时间常数,80℃硼酸水溶液中的阻抗模值较小;随时间的延长,304L不锈钢的均匀腐蚀速率逐渐降低,并且维持在较低的腐蚀速率。     

镁合金表面MgF_2/HA复合涂层的体外降解性能

为改善镁合金的耐蚀性和生物相容性,利用化学处理和电化学沉积法在镁合金AZ31表面制备MgF_2/HA复合涂层。采用Hank’s仿生溶液中浸泡和电化学阻抗(EIS)的方法,结合浸泡过程中涂层EIS谱和表面形貌成分的变化,研究MgF_2/HA涂层的体外降解行为。结果表明:在Hank’s仿生溶液浸泡过程中,涂层电化学阻抗谱的高频容抗弧明显减小,涂层电阻随浸泡时间而降低。浸泡至5 d时,出现感抗弧,涂层表面区域产生腐蚀孔核。浸泡至8 d时,镁合金基体发生点蚀,点蚀产生的腐蚀产物在孔中堆积形成胞状突起。浸泡至12 d时,Cl-渗透至镁合金基体,涂层表面形成MgCl_2结晶。浸泡过程中,表面涂层未发生脱落和明显的溶解,降解以溶液渗透至基体,然后发生局部点蚀为主。     

多弧离子镀Al涂层对310不锈钢在熔融碳酸盐中的腐蚀的影响

采用多弧离子镀技术在310不锈钢表面制备Al涂层并经高温扩散退火,在合金表面形成铝化物涂层.采用电化学阻抗谱技术研究其在650℃熔融碳酸盐中的腐蚀行为.结果表明,310不锈钢的腐蚀电化学阻抗谱由双容抗弧组成,随着时间的延长,在低频端出现传质控制的特征.而涂层的腐蚀电化学阻抗谱仍由双容抗弧组成,但阻抗值明显增加.铝涂层的优异抗腐蚀性能是由于在表面形成了连续的保护性LiAlO_2(Al_2O_3)膜.     

模拟酸雨组分对1Cr18Ni9Ti不锈钢土壤腐蚀行为的影响

利用极化曲线和电化学阻抗谱(EIS)等方法研究了模拟酸雨组分对1Cr18Ni9Ti不锈钢在土壤中腐蚀行为的影响。结果表明,酸雨组分对1Cr18Ni9Ti不锈钢腐蚀行为影响显著。随着SO42-与NO3-浓度比的减小,不锈钢的腐蚀速率减小,说明硫酸型酸雨对本体系的腐蚀性明显强于硝酸型酸雨。不锈钢的电化学阻抗谱表现为双容抗弧,其腐蚀过程主要受氧扩散过程控制。     

非晶合金Zr55Al10Cu30Ni5在3.5%NaCl溶液中的电化学行为

利用电化学极化曲线方法和电化学阻抗（EIS）技术研究了非晶合金Zr55Al10Cu30Ni5在3.5%NaCl溶液中的电化学行为。极化曲线测试结果表明，非晶合金Zr55Al10Cu30Ni5在3.5%NaCl溶液中具有很好的耐蚀性能，阳极过程表现出钝化特征，当极化电位很高时，非晶合金出现了点腐蚀。电化学交流阻抗测试表明，在阴极极化，开路电位和钝化电位下，非晶合金的Nyquist图由单容抗构成，具有很高的电荷转移电阻，表现出优良的耐蚀性，在点蚀电位附近和点蚀电位区EIS分别有两个时间常数和三个时间常数，非晶合金在3.5%NaCl溶液中浸泡12h后，耐蚀性能有所下降。     

添加Al粉对有机硅树脂涂层性能的影响

应用电化学方法研究了在有机硅涂料中添加不同含量的铝粉对其性能的影响.实验结果表明，添加5%和25%Al粉的有机硅涂层在相当长浸泡时间内保持优良的耐蚀性能.Al粉明显提高了304不锈钢的电化学反应电阻.添加Al粉的有机硅涂层的耐蚀性与其含量之间不是简单的线性关系.     

γ_N相在硼酸缓冲溶液中的腐蚀与钝化性能

采用等离子体源渗氮技术在304L奥氏体不锈钢表面制备高氮面心结构的γ_N相层,利用阳极极化曲线和电化学阻抗谱(EIS)研究γ_N相在pH=8.4硼酸缓冲溶液中的腐蚀行为。结果表明:γ_N相的阳极极化曲线呈现出自钝化-过钝化溶解过程,自腐蚀电位Ecorr较原始不锈钢提高了75mV,维钝电流密度Jp降低近一个数量级,耐蚀性能明显提高。与原始不锈钢钝化膜相比,γ_N相钝化膜的EIS容抗弧直径及|Z|值增大,相位角平台变宽,其电荷转移电阻Rct增至1.064×107Ω·cm2,双电层电容Cdl降至65.4μF/cm2,说明γ_N相钝化膜更致密,表现为近电容特性。随着浸泡时间增加,γ_N相钝化膜的Rct稳定在107Ω·cm2量级,具有良好的稳定性。     

Effect of hydrochloric acid on pickling of hot-rolled 304 stainless steel in iron chloride-based electrolytes

Weight loss, corrosion potential and EIS measurements were performed to understand the role of HCl in the pickling of oxidised 304 stainless steel in iron chloride-based electrolytes. The surface finish was analysed with SEM-EDX. The oxidised 304 stainless steel is active on immersion, resulting in a low corrosion potential and a high weight loss. After certain duration the stainless steel either remains active or becomes passive depending on HCl content. At low HCl contents, an ongoing active-to-passive transition results in localised corrosion at pits, grain boundaries and honeycombed recesses. The corrosion potential becomes high and the weight loss is suppressed. The weight loss decreases in the initial stage and rises on extended pickling with adding HCl. Because of anodic brightening, the 304 stainless steel is always active as HCl is concentrated. In contrast with the material that is passivated, the charge transfer resistance is considerably low and the double layer capacitance is large during that brightening.     

Corrosion behaviors of arc spraying single and double layer coatings in simulated Dagang soil solution

Three kinds of single layer coatings of Zn, Zn15Al, 316L stainless steel and two kinds of double layer coatings with inner layer of Zn or Zn15Al and outer layer of 316L stainless steel by arc spraying were developed to protect the metal ends of prestressed high-strength concrete (PHC) pipe piles against soil corrosion. The corrosion behaviors of the coated Q235 steel samples in the simulated Dagang soil solution were investigated by potentiodynamic polarization, electrochemical impedance spectroscopy (EIS) and natural immersion tests. The results show that the corrosion of the matrix Q235 steel is effectively inhibited by Zn, Zn15Al, Zn+316L and Zn15Al+316L coatings. The corrosion rate value of Zn15Al coated samples is negative. The corrosion products on Zn and Zn15Al coated samples are compact and firm. The corrosion resistance indexes of both Zn and Zn15Al coated samples are improved significantly with corrosion time, and the latter are more outstanding than the former. But the corrosion resistance of 316L coated samples is decreased quickly with the increase in immersion time. When the coatings are sealed with epoxy resin, the corrosion resistance of the coatings will be enhanced significantly.     

Electrochemical Evaluation of Corrosion on Borided and Non-borided Steels Immersed in 1 M HCl Solution

In this study the corrosion resistances of AISI 1018 and AISI 304 borided and non-borided steels were estimated using polarization resistance and electrochemical impedance spectroscopy (EIS) techniques. Boriding of the steel samples was conducted using the powder-pack method at 1223 K with 6 h of exposure. Structural examinations of the surfaces of the borided steels showed the presence of a Fe₂B layer with isolated FeB teeth on the AISI 1018 steel, whereas a compact layer of FeB/Fe₂B was formed on the AISI 304 steel. Polarization resistance and EIS of the borided and non-borided steels surfaces were performed in a corrosive solution of 1 M HCl. The EIS data were analyzed during 43 days of exposure to the acid solution. Impedance curves obtained during this period for the borided and non-borided steels were modeled using equivalent electrical circuits. The results of both electrochemical techniques indicated that boride layers formed at the steel surfaces effectively protect the samples from the corrosive effects of HCl. The main corrosion processes observed on the boride layers were pitting and crevice corrosion.     

304不锈钢晶间腐蚀过程中的电化学阻抗谱特征

用电化学阻抗谱（EIS）方法研究了固溶态、敏化态304不锈钢在0．5mol／LH2SO4＋0．01mol／LKSCN溶液中的阻抗谱特征．研究表明，不锈钢在不同极化电位下的阻抗谱呈现活性溶解、活化一钝化、钝化及再活化的特征．达到再活化之前，固溶态和敏化态的不锈钢在0．5mol／LH：SO4＋0．01mol／LKSCN溶液中呈现相同的EIS特征；而在再活化区，钝化膜局部溶解，EIS图有两个容抗弧，低频容抗弧延伸到第二象限，呈现负电阻特征，低频下敏化态比固溶态不锈钢阻抗模值小一个数量级．     

Study of the electrochemical behaviour of 304 stainless steel in postgate medium in the presence and absence of desulfovibrio desulfuricans

A comparative study has been undertaken on the behaviour of AISI 304 steel in Postgate medium with and without the presence of Desulfovibrio desulfuricans subspecies desulfuricans bacteria (strain DSM 642). Electrochemical studies were carried out with open circuit potential measurements, linear polarization, electrochemical impedance spectroscopy (EIS) and scanning electronic microscopy (SEM). In Postgate medium without bacteria, and as expected in stainless steels, the formation is observed of a protective surface passive film on the AISI 304 steel. On measuring the corrosion potentials (E_corr), it is noted that the potential tends to rise with the immersion time, and in the impedance graphs an increase is observed in the charge transfer resistance and a higher phase angle with respect to the other systems tested. However, in Postgate medium with Desulfovibrio desulfuricans (strain DSM 642), the tendency of the corrosion potentials (E_corr) is not uniform, though the recorded values are less noble than those for the medium without bacteria. A variation is observed in the properties of the layer of corrosion products in the presence of bacteria as the immersion time advances (due to the effects caused by the formation of corrosion products which gives rise to changes in the corrosion speed).     

Study of the correlation between corrosion resistance and semi‐conducting properties of the passive film of AISI 316L stainless steel in physiological solution

In this work the corrosion resistance of AISI 316L biomedical stainless steel was assessed through electrochemical impedance spectroscopy (EIS) measurements in Hanks' solution at 37 °C. Specimens were immersed in the electrolyte during 21 days. Semi‐conducting properties of the passive film naturally formed on the surface of the metallic material during the test were evaluated through the Mott–Schottky approach. The aim was to investigate the correlation between corrosion resistance and semi‐conducting properties in the physiological solution. The corrosion resistance was found to decrease with the immersion time. The density of defects in the passive film increased accordingly as indicated by the Mott–Schottky plots. The passive film presented a semi‐conducting behavior with a duplex character. Above the flat band potential the behavior was typical of an n‐type semiconductor whilst below such value it was typical of a p‐type semiconductor. The results from EIS measurements and Mott–Schottky were in good agreement, suggesting that the corrosion resistance of biomedical stainless steels may be associated with the semi‐conducting properties of the passive films formed during immersion in physiological medium.     

The effect of temperature on the galvanic corrosion of the copper/AISI 304 pair in LiBr solutions under hydrodynamic conditions

The corrosion behaviour of copper and AISI 304 stainless steel and the galvanic corrosion generated by the copper/AISI 304 pair, have been studied by electrochemical methods. These materials have been tested in an 850 g/L LiBr solution at different temperatures (25-75 °C) and at different Reynolds numbers (1456-5066) in order to study their performance in absorption machines. Results show that copper was always the anodic element of the pair and its corrosion resistance decreases due to the AISI 304 stainless steel galvanic effect. Galvanic corrosion increases with temperature and Reynolds number. However, it was proved that the effect of temperature on galvanic corrosion is more influential than the Reynolds number effect. This fact is also certain for corrosion of uncoupled copper and for corrosion of AISI 304 stainless steel. Experimental values of the corrosion current densities fit well the Arrhenius plot at all the Reynolds numbers analysed and a potential relation between the corrosion current densities and the Reynolds number has been found.     

The corrosion behavior of zinc-rich paints on steel: Influence of simulated salts deposition in an offshore atmosphere at the steel/paint interface

The corrosion behavior of an epoxy zinc-rich paint on interface-contaminated carbon manganese-silicon steel was studied. SEM observation on the cross-section of the paint indicates that the zinc corrosion products grew from the surface to the inner of the paint and salts contamination promoted the growth at locations close to the steel/paint interface. The results of electrochemical impedance spectroscopy show that the corrosion resistance of the contaminated paint was significantly influenced by diffusion of zinc corrosion products during the initial stage of immersion, and diffusion of iron corrosion products at the end of immersion. Three transmission line models were applied to account for the corrosion process of the uncontaminated and contaminated zinc-rich paints.     

The effect of ionic peneration on semiconducting behaviour of temporarily protective oil coating on the surface of AISI 304 stainless steel

In this paper, the semiconducting behaviour of temporarily protective oil coatings on the surface of naked and prepassivated AISI 304 stainless steel immersed in 3% aqueous NaCl solution was studied by utilizing potential‐capacitance methode, Mott‐Schottky analysis and impedance analysis. It was pointed out that the temporarily protective oil coating behaves as a semiconductor during its degradation. The ionic penetration and the substrate greatly affect the conduction behaviour of the oil coating. On the surface of naked AISI 304 stainless steel, the oil coating behaves as a n‐type semiconductor. With increasing immersion time, the donor density of the space charge layer in the temporarily protective oil coating increases from 10¹⁹ to 10²⁵ m^?3. However, on the surface of the prepassivated substrate the space charge layer in the oil coating is significantly affected by the oxide on the steel electrode. In this case immersion time does not influence the density of charge carriers in the oil coating (10²¹ m^?3). Impedance analysis also verify above results.