INFLUENCE OF NaCl DEPOSITION ON ATMOSPHERIC CORROSION OF A3 STEEL IN THE PRESENCE OF SO_2

The regularities of atmospheric corrosion of A3 steel deposited with different amount of NaCl exposed to the air containing 1ppm SO2 at 80%RH and 25℃ were studied in laboratory. NaCl can accelerate the corrosion of A3 steel obviously under such condition. The relationship between the weight loss of A3 steel and the amount of NaCl deposition can be well described by using a quadratic function. Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), Scanning electron microscopy and electron dispersion X-ray analysis (SEM/EDAX) were used to characterize the corrosion products. In the absence of NaCl, FeSO4 · xH2O is the dominant corrosion products, while Fe3O4, FeSO4·H2O, β-FeOOH and γ-FeOOH dominate in the presence of NaCl.

Influence of NaCl Deposition on Atmospheric Corrosion of A3 Steel

Regularity of the initial atmospheric corrosion of A3 steel in the presence of NaCI was investigated. The results showed that NaCI can accelerate the corrosion of A3 steel. Dry mass gain of A3 steel in the presence of NaCI deposition increases with the exposure time, which can be correlated by using exponential decay function. The relationship between dry mass gain and amount of NaCI deposition at a certain exposure time follows a quadratic function. More amount of NaCI deposition will slow down the corrosion rate to some extent after exposure for a certain time. SEM/EDAX was used to characterize the corrosion surface and products. The surfaces of the NaCI treated A3 steel were obviously uneven, and some tiny crevices appear in the corrosion products that could help O2 transmit to the inner layer. The amount of oxygen in atomic percentage in the corrosion products increases with the amount of NaCI deposition.

Atmospheric Corrosion of Steel A3 Deposited with Ammonium Sulfate and in the Presence of Sulfur Dioxide

A laboratory study of the atmospheric corrosion of carbon steel deposited with (NH4)2SO4 in the presence of SO2 is reported. The different levels of (NH4)2SO4 (0, 15, 30, 45, 60 μg·cm-2) were added on the surface of the samples before the exposure. The corrosion was investigated by a combination of gravimetry, Fourier transform infrared spectroscope and scanning electron microscopy. A detailed knowledge about the corrosion products was acquired, both quantitatively and qualitatively. The results show that the metal loss increased and the increasing tendency of corrosion rates slowed down with the increasing exposure time. The phase constituents of the corrosion products are mainly α-FeO(OH), γ-FeO(OH), and δ-FeO(OH).

Effect of CO_2 on Atmospheric Corrosion of UNS G10190 Steel under Thin Electrolyte Film

The atmospheric corrosion of UNS G10190 steel under a thin electrolyte film in the atmosphere polluted by CO_2, has been studied in the lab using an atmospheric corrosion monitor (ACM) in combination with XRD and SEM observations of the surface of steel. The ACM study indicated that the corrosion rate of the steel increased with increasing carbon dioxide concentration. The XRD and SEM observations showed that no carbonate was found in the corrosion product on the steel surface. The corrosion product consisted of two layers, i. e., inner and outer layer. From the experimental results, it was concluded that CO_2 played an enhancing role in the atmospheric corrosion of UNS G10190 steel. The film of the corrosion product showed slight protection.

凝露状态下SO_2对A3钢腐蚀机理的影响

采用红外光谱、电化学交流阻抗和扫描电镜等方法研究了大气中对金属腐蚀性最强的污染物SO2 在凝露状态下对A3钢的腐蚀作用规律 .结果表明 ,A3钢在加SO2 试验环境中腐蚀失重随试验时间延长呈正指数变化规律 ;试样表面呈龟裂状腐蚀形貌 ,红外光谱的分析结果显示出腐蚀产物为FeSO4 ·7H2 O、Fe2 (SO4 ) 3 ·9H2 O和γ -FeOOH ,还含有δ -FeOOH及少量的Fe(OH) 2 和Fe3 O4 .A3钢在未加SO2 试验环境中腐蚀失重随时间呈直线变化规律 ;腐蚀产物主要为Fe2 O3 和γ -FeOOH ;试样表面未形成连续的腐蚀产物膜 .

二氧化碳在A3钢大气腐蚀中的作用

通过电化学法并结合 ＸＲＤ及 ＳＥＭ；研究了大于临界相对湿度条件下， ＣＯ_２浓度对 Ａ３钢在薄层液膜下大气腐蚀的影响电化学实验结果表明，Ａ３钢的大气腐蚀速率随ＣＯ_２浓度的上升而增加.Ｘ射线衍射分析及ＳＥＭ观察表明，金属表面腐蚀产物中无碳酸盐生成；腐蚀产物在金属表面分为内、外双层结构，ＣＯ_２在Ａ３钢表面的吸附是不均匀的．故ＣＯ_２对金属的大气腐蚀起着加速作用，腐蚀产物膜对金属的保护作用微弱，同时提出了

微量SO_2条件下硫酸铵颗粒沉积对A3钢大气腐蚀的影响

研究微量 SO2 存在的实验室模拟条件下 ,沉积不同质量硫酸铵颗粒的 A3钢的大气腐蚀行为 ,发现沉积硫酸铵颗粒的 A3钢试样比其空白试样的腐蚀严重 ,而且随着沉积量的增加 ,样品的腐蚀现象更为严重。用 IR和 SEM分析研究了不同周期样品表面的结构和形貌 ,发现腐蚀主要沿着硫酸铵颗粒沉积的地方进行 ,腐蚀产物的颗粒逐渐变大 ,随着腐蚀时间的延长 ,样品表面的铵根离子逐渐减少 ,腐蚀产物主要由 α- Fe O (OH) ,γ- Fe O (OH)和 δ- Fe O(OH)

SO_2质量分数对污染海洋大气环境中高强钢E690腐蚀行为的影响

采用干湿交替腐蚀试验方法,结合电化学测试、锈层截面和腐蚀产物X射线衍射(X-ray diffraction,XRD)分析,研究SO_2质量分数对E690钢在模拟污染海洋大气环境中腐蚀行为的影响。结果表明,海洋大气环境中的SO_2改变了E690钢海洋大气腐蚀的电化学机制,使得极化曲线的阳极分支由弱钝化特征转变为活性溶解特征,阴极分支由氧扩散过程控制转变为氧扩散和析氢反应共同控制,因而大大促进了阳极和阴极的电化学反应过程。同时,SO_2又显著促进α-Fe OOH的生成和Ni、Cr合金元素在内锈层中的富集,大大促进锈层的致密化,使均匀腐蚀速率逐渐减低,并促进锈层底部点蚀坑的生长。随着模拟溶液中Na HSO_3浓度的增加,E690钢在60 d内的平均腐蚀速率逐渐增加,当Na HSO_3浓度达到0.03 mol/L时,又出现一定程度的降低;同时,锈层底部的点蚀坑随Na HSO_3浓度的增加显著长大。

Zn在SO_2环境中大气腐蚀初期表面特性研究

采用扫描电镜 (SEM EDAX)和显微红外光谱技术对Zn在相对湿度为 90 %和 0 .9× 1 0 -6SO2 的控制气氛条件下初期腐蚀表面和腐蚀产物进行了研究 .1 0h以后腐蚀表面呈现均匀分布的凹凸形貌特征 ,直到数日后开始萌生局部腐蚀 .

万宁滨海与西沙群岛大气腐蚀性对比研究

统计分析了西沙群岛和万宁试验站近海场的润湿时间、空气中二氧化硫和氯离子沉积速率,根据环境因素法和标准金属法评定了两地的大气腐蚀性,两地的大气腐蚀等级同为C5级,但西沙群岛的腐蚀性稍弱于万宁试验站近海场。Q235钢、镀镍钢、镀铬钢、不锈钢钝化件在两地的试验结果证实了上述结论,试验结果表明,万宁试验站近海场积累的大量试验数据可应用于西沙群岛。

含SO_2大气中湿度对低碳钢腐蚀行为的影响

采用模拟污染大气腐蚀系统,利用光学显微镜、SEM、XRD和XPS等研究了湿度对含体积分数为5×10-6的SO2环境中20低碳钢腐蚀形貌和腐蚀产物生长过程的影响。结果表明:在不同湿度环境中,腐蚀产物均主要由α-FeOOH、γ-FeOOH、FeSO4、Fe3O4、γ-Fe2O3组成;随湿度增大,FeOOH含量增多,低碳钢的腐蚀速率增大;在相对湿度为65%,75%时,腐蚀曲线分为指数增加和线性增加2个阶段,在85%,95%时,腐蚀曲线符合线性增长规律;在相对湿度为65%的环境中,腐蚀产物主要以腐蚀圈形式生长,随着相对湿度增加,腐蚀圈周围有短小丝状腐蚀产物出现;在相对湿度为95%时主要为丝状腐蚀产物,其上伴随有胞状腐蚀产物生成,且在胞状腐蚀产物下存在明显的腐蚀坑。

Super304H钢在含1.5%SO_2模拟烟气中的腐蚀行为研究

目的研究Super304H钢在650℃和700℃模拟烟气中的腐蚀行为和机理。方法将Super304H钢试样置于含SO2(体积分数1.5%)的模拟烟气中,间隔一定时间取出样品称量,获得腐蚀动力学曲线。采用XRD、SEM和EDS分析不同腐蚀阶段的腐蚀产物形貌、成分和物相组成。结果腐蚀初期,Super304H钢在700℃下的腐蚀速率明显比650℃下的快,腐蚀过程中,腐蚀产物不断生成和剥落。650℃时,样品初期的主要成分为Cr_2O_3和Fe2O3,随腐蚀时间的延长,生成了Fe_3O_4;700℃时的腐蚀产物剥落更明显。腐蚀产物具有双层结构,主要由Fe2O3、Cr_2O_3、Fe_3O_4和少量(Ni,Cr)Fe_2O4、Cu Fe_2O4尖晶石类化合物组成,在腐蚀产物内层生成了硫化物。结论 Super304H钢在650℃和700℃含SO2(1.5%)的模拟烟气中,腐蚀产物不断生成和剥落,导致腐蚀加速。

珠光体组织对重轨钢U71Mn腐蚀行为的影响

通过实验室加速腐蚀试验研究了不同珠光体片层间距重轨钢在模拟大气环境中的腐蚀行为,采用场发射电镜、XRD、电化学测试等方法对重轨钢组织和腐蚀结果进行了表征。不同冷却制度下所得实验用U71Mn重轨钢珠光体片层间距为155 nm、241 nm、340 nm、446 nm。随腐蚀时间延长和珠光体片层间距减小,腐蚀失重和腐蚀速率明显下降,珠光体片层间距为155 nm时,腐蚀速率最小,为0.0014 mg·cm^(-2)·h^(-1)。四种试样锈层中均含有α-FeOOH、γ-FeOOH、Fe_(3)O_(4),当珠光体片层间距减小到241 nm以下,α-FeOOH峰值明显增强,腐蚀产物中最先出现少量α-Fe_(2)O_(3),锈层形貌较为致密。珠光体组织片层间距从446 nm减小到155 nm,形成致密的保护性锈层的时间从240 h提前120 h,内锈层厚度和致密性明显提高,腐蚀480 h后珠光体片层间距最小的实验钢腐蚀电流最小,腐蚀电位最大,抗大气腐蚀性能最好。

Evaluation of increasing service life of epoxy zinc-rich coating on 3 wt.%Ni-advanced low-alloy steel in marine atmospheric environment

The addition of Ni element into steel to prolong the service life of coated steel was investigated in marine atmospheric environment by laboratory simulated accelerated experiment.The scanning electron microscope and electron probe microanalysis combined with electrochemical impedance spectroscopy were used to characterize coated steel properties and examined the anti-corrosion performance.The results showed that 3 wt.%Ni-advanced steel(3Ni steel)substrate obviously delayed the failure time of coating compared to carbon steel,therefore prolonging the service life of coating on the steel.X-ray diffraction patterns for the corrosion products under the scratched coating on 3Ni steel exhibited that FeNi_(2)O_(4) and Fe_(2)O_(3) occurred in the corrosion product of 3Ni steel.It was also found that Ni element enriched in the product layer through analyzing the appearance and composition of corrosion products by electron probe micro-analysis.Chloride ions were blocked out of product by the enrichment of Ni element in rust layer.

XDSS合金配酸系统在硫酸法钛白粉生产中的应用

详细探讨了硫酸的腐蚀特性及机理。介绍了高硅XDSS合金的性能及XDSS合金配酸系统在硫酸法钛白粉生产中的应用。XDSS合金配酸系统具有维护方便、效率高、全生命周期成本低的特点,值得在硫酸法钛白粉配酸过程中推广应用。

O_(3)/SO_(2)复合大气环境中Q235B钢的腐蚀演化特性

采用干/湿交替的实验方法模拟大气腐蚀过程。运用X射线衍射、3D激光测量显微镜、电化学阻抗谱以及极化曲线等手段,研究了O_(3)/SO_(2)复合大气环境中Q235B钢的腐蚀演化特性。结果表明,O3和SO2的交互作用对Q235B钢的腐蚀有明显的抑制作用。腐蚀演化特性方面,当模拟环境中Na_(2)SO_(3)浓度为0.01 mol/L时,O_(3)/SO_(2)复合大气环境中Q235B钢的腐蚀速率呈先迅速增大而后缓慢减小的趋势;当模拟环境中Na_(2)SO_(3)浓度为0.05 mol/L时,O_(3)/SO_(2)复合大气环境中Q235B钢的腐蚀速率呈先缓慢增大后迅速下降的趋势;当模拟环境中Na_(2)SO_(3)浓度为0.10 mol/L时,O_(3)/SO_(2)复合大气环境中Q235B钢的腐蚀速率呈先增大而后缓慢减小的趋势。相比于不含O3的大气环境,当模拟大气中SO2含量较低时,O_(3)和SO_(2)的交互作用会促进具有保护性腐蚀产物中α-FeOOH生成;而当大气中SO_(2)含量较高时,O_(3)对腐蚀产物相组成影响不明显。