特殊排水管道防腐保护层局部腐蚀原因分析及处理措施

将排水管道用Q235低碳钢,在无氧条件下浸泡在NaHCO3溶液中,研究NaHCO3浓度对其极化曲线、开电位、电化学阻抗谱、腐蚀产物及其形貌的影响。结果表明,当碳酸氢钠溶液浓度高于0.02 mol/L时,Q235低碳钢表面被钝化,低于这个值时,Q235低碳钢将处于活性溶解状态。     

建筑用钢在碳化混凝土孔溶液中的腐蚀行为研究

制备了碳化作用下不同pH值的混凝土孔溶液,研究了建筑用HRB335钢的腐蚀性能。结果表明,在pH值较低时(pH=10.0),钢表面形成均匀的腐蚀产物。随着pH值的升高(pH=10.5或11.5),钢表面形成局域腐蚀产物。当溶液pH值达到12.5时,含钙氧化铁和CaCO3沉积膜附着在材料钝化膜表面,提高了钢的耐蚀性。     

模拟高放废物地质处置环境下重碳酸盐浓度对低碳钢活化/钝化腐蚀倾向的影响

在除氧的HCO-3溶液中,采用原位测量开路电位方法研究了HCO-3浓度对低碳钢腐蚀活化/钝化状态的影响,用SEM观察了低碳钢电极在除氧的HCO-3溶液中长期腐蚀后的表面形貌,用电化学阻抗谱(EIS)方法研究了电极的腐蚀演化特征及规律,用XRD方法检测了腐蚀产物的相组成.结果表明,低碳钢的开路电位随浸泡时间的延长以及HCO-3浓度的升高而升高;长期浸泡后,在0.01 mol/L HCO-3溶液中低碳钢的阳极溶解处于极限扩散状态,而在高于0.02 mol/L HCO-3溶液中处于钝化状态;锈层的主要腐蚀产物为a-FOOH和Fe3O4.     

碳钢在点蚀/缝隙腐蚀闭塞区模拟溶液中的腐蚀行为

研究了低碳钢在点蚀孔/缝隙腐蚀闭塞区模拟溶液中的腐蚀 行为.结果表明低碳钢在pH等于2～4的模拟闭塞区溶液中,阴极过程由氢离子的扩散步骤控 制,阴极去极化起着主要作用.当pH值小于2时,阴极过程表现为活化特征.阳极溶解过程遵 循着Bockris机理.碳钢在闭塞区的腐蚀不存在临界pH值和临界Cl-浓度,腐蚀速度(V c)的对数与pH值呈线性关系.闭塞区内溶液pH的微小变化,对腐蚀速度有明显的影响.外部 溶液中的Cl-离子迁入闭塞区后,会促使溶液pH下降.     

重碳酸盐溶液中SO_4~(2-)和Cl~-对低碳钢活化/钝化腐蚀行为的影响

在除O_2的0.1 mol/L NaHCO_3,0.1 mol/L NaHCO_3+0.1 mol/L Na_2SO_4以及0.1 mol/L NaHCO_3+0.1 mol/L NaCl溶液中,用恒电位法在低碳钢电极表面制备腐蚀产物,并原位监测低碳钢的开路电位,用SEM观察腐蚀形貌,用XRD确定腐蚀产物的相组成.结果表明.在0.1 mol/L NaHCO_3溶液中,低碳钢的开路电位最终处于再钝化区间,其表面未观察到明显的腐蚀现象;在0.1 mol/L NaHCO_3+0.1 mol/L Na_2SO4溶液中,低碳钢的开路电位最终处于再活化区间,其表面发生均匀腐蚀;在0.1 mol/L NaHCO_3+0.1 mol/L NaCl溶液中,低碳钢的开路电位最终亦处于再活化区间,而其表面却发生局部腐蚀,XRD结果表明,低碳钢表面的腐蚀产物主要为Fe_3O_4和α-FeOOH.     

H2S水溶液中的腐蚀与缓蚀作用机理的研究Ⅲ.不同pH值H2S溶液中碳钢的腐蚀电化学行为

利用极化曲线和阻抗技术 ,对低碳钢在不同pH值H2 S溶液中的腐蚀电化学行为进行了研究。结果表明 ,在溶液pH值较低时 ,腐蚀电极主要受阳极酸性溶解过程控制 ,表面无硫化物沉积 ,其阻抗谱除高频容抗弧外 ,低频有一感抗弧存在 ;随pH的升高 ,腐蚀电位明显负移 ,电流密度减小 ,表面出现硫化物的不连续沉积 ,腐蚀因溶液pH值的增加和硫化物的沉积而减小 ,电极过程主要受硫化物的生长所控制 ;在pH值为 6.2时 ,由于HS 的阴极去极化 ,腐蚀电流增加 ;当pH大于 7后 ,电极表面因氧化膜的生成而呈现钝化特征 ,极化电阻显著增加。基于溶液中HS 同OH 的竞争吸附 ,提出可能的腐蚀历程 ,据此可解释有关实验事实。     

X70钢在模拟土壤溶液中点蚀敏感性影响因素交互作用研究

通过正交试验法,采用动电位扫描技术研究了Cl-浓度、pH值和温度对X70钢在HCO3-+Cl-介质中电化学行为的交互影响.结果表明:Cl-浓度、pH值、温度三因素对X70管线钢在模拟土壤溶液中腐蚀及钝化行为影响较大,三因素对其点蚀敏感性影响依次为:pH值Cl-浓度温度;在Cl-浓度为0.010 mol/L、温度35℃、pH值为8.2的模拟土壤溶液中X70钢的点蚀敏感性最大,钝化区间较窄(-0.257~0.204 V),当电位超过0.204 V时已处于过钝化状态.     

镍基合金G3在高含H2S／CO2环境中的腐蚀影响因素研究

针对目前高含H2S和CO2油气田开发中的油套管严重腐蚀问题,通过动电位扫描、扫描电镜(SEM)分析腐蚀产物膜等手段,研究了在高含H2S和CO2腐蚀环境中,CO2、pH值、Cl-等不同因素对镍基合金G3腐蚀行为的影响.结果表明:Cl-不利于G3钝化膜的形成,且使腐蚀加剧;CO2的加入促进了G3的腐蚀,pH值的增加使G3的自腐蚀电位出现较大负移.并影响了腐蚀产物膜的稳定性.     

碳化对模拟混凝土孔溶液中HRB335钢腐蚀行为的影响

应用电化学阻抗谱、循环伏安与动电位极化等方法研究了碳化后模拟混凝土孔溶液pH值的变化对钢筋腐蚀电化学行为的影响.结果表明,随着pH值的下降钢筋表面钝化膜的稳定性与耐蚀性不同程度地降低.当模拟液pH值为12.5与11.5时,钝化膜的稳定性处于因pH值降低导致的钝化膜溶解与表面沉积物CaCO3或含钙氧化物CaFe2O4等耐...     

pH值对碳钢在高含硫油田水中腐蚀行为的影响

采用电化学测试方法和动态腐蚀失重实验并结合扫描电镜和能谱分析, 研究不同pH值下J55钢在高含硫油田水中的腐蚀行为。结果表明, 随着溶液pH值升高, J55钢阴极去极化作用减弱, 腐蚀速率下降。当pH值在5.6~7.2时, 腐蚀产物主要是疏松且易脱落的粗晶粒四方硫铁矿FeS_1-x, 无法在碳钢表面形成保护膜, 形成大量腐蚀坑, 使碳钢表面腐蚀较严重;当pH值在8.7~11.0时, 腐蚀产物主要是氧化铁, 在碳钢表面形成了致密的保护膜, 阳极有明显的钝化现象, 碳钢表面腐蚀轻微。     

A3钢在富营养化东湖水中初期腐蚀研究

    以A3钢为研究对象,采用失重实验和电化学技术研究了A3钢在富营养化东湖水中的腐蚀行为.结果表明：A3钢在实验过程中腐蚀电流随时间增长逐渐减小;自腐蚀电位先降后升,而极化电阻逐渐增大,说明电极表面刚开始处于活化状态,然后电极表面“保护膜”不断生长,将电极表面覆盖,减缓了基体的腐蚀;电化学方法计算出富营养化水中A3钢的腐蚀电流与线性极化电阻的比例常数B值为23.6242;通过XPS分析得出A3钢腐蚀产物的成分为FeOOH,Fe³⁺与C、N、S结合的有机产物和FeSO₄,其中Fe²⁺/Fe³⁺=0.24.     

Corrosion of carbon steel in concentrated LiNO3 solution at high temperature

The corrosion of carbon steel in concentrated LiNO₃ solution at high temperature was investigated by a weight loss method. Results showed that increasing temperature and pH would increase the corrosion rate, and increasing concentration and adding Li₂CrO₄ would reduce the corrosion rate. The corrosion in LiNO₃ solution was general corrosion and the corrosion products were composed of Fe₃O₄ and Fe₂O₃. A compact passive layer comprising of Cr₂O₃, Fe₃O₄ and Fe₂O₃ was observed with adding Li₂CrO₄, and it could effectively depress the corrosion. The carbon steel corrosion in LiNO₃ solution was much smaller than that in LiBr solution.     

Impedance of Cr18Ni10 stainless steel in sulphate solutions after a low‐temperature plasma nitriding

The 00Cr18Ni10 stainless steel was examined before and after plasma nitriding in a 80%N₂/20%H₂ gas mixture at 425°C for 30 h, resulting in the formation of a supersaturated solid solution of nitrogen in austenite (S phase) with 12.9 wt.% N at the surface. Electrochemical measurements were made on the as‐nitrided surface and after abrasion to various depths. Polarisation curves and impedance were measured in 0.1 M Na₂SO₄ acidified to pH 3.0; some measurements were also made at pH 6 and 9. It was found that nitrogen decreased the corrosion resistance of the steel in the acidified solution (pH 3.0), but increased it in the neutral and near‐neutral solutions (pH 6.0 and 9.0). The deleterious effect of nitrogen at pH 3.0 was at potentials of the active state much stronger and more dependent on the nitrogen concentration than in the passive state. It was suggested that the increased anodic reactivity of the nitrided steel in the active state is inherent for the lower thermodynamic stability of the supersaturated solid solution of nitrogen, whereas the increased corrosion resistance in the neutral and near‐neutral sulphate solutions is associated with the effect of nitrogen on anodic films.     

An electrochemical investigation of Fe75B25-xSix amorphous alloys

The glassy alloys of the family Fe₇₅B_25-xSi_x exhibit a low corrosionresistance. Their corrosion rate decreases with increasing solution pH and they undergo the active/passive transition only when pH attains 8.4. There is a minor effect of Si on the corrosion rate at the open circuit potential. However, remote from E_corr in acidic solutions Si enhances the active dissolution at anodic potentials and suppresses the hydrogen evolution. On the other hand the ability to passivate and the stability of the passive state increases distinctly with Si concentration.     

Corrosion of X65 steel in CO2-saturated oilfield formation water in the absence and presence of acetic acid

Electrochemical corrosion behavior of X65 steel in CO₂-saturated formation water in the absence and presence of acetic acid was studied by electrochemical measurements, scanning vibrating micro-electrode (SVME), localized electrochemical impedance spectroscope (LEIS) and surface analysis techniques. It is found that, when steel is immersed in formation water, the dissolution of Fe dominates the anodic process and the steel is in active dissolution state. Adsorption of intermediate product on the electrode surface results in generation of an inductive loop in the low frequency range of EIS plot. As corrosion proceeds, the concentration of Fe²⁺ in the solution increases. When the product of [Fe²⁺] × [] exceeds solubility product of FeCO₃, FeCO₃ will deposit on the electrode surface, and protects the steel substrate from further corrosion. The steel is in a “passive” state. When the electrode surface is completely covered with FeCO₃ film, the inductive loop in the low frequency range disappears. In the presence of acetic acid in formation water, the cathodic reaction will be enhanced due to the direct reduction of undissociated acetic acid. Addition of acetic acid degrades the protectiveness of corrosion scale, and thus, enhances corrosion of steel by decreasing the FeCO₃ supersaturation in solution.     

亚铵法制浆过程中碳钢蒸球的腐蚀行为与防腐蚀措施

在亚铵法制纸浆蒸煮过程中升温到120℃附近时,碳钢蒸球内壁将由活化转为钝化。钝化膜表层为亚硫酸亚铁铵结晶层,里层为铁的氧化物层。活化碳钢的表面大部份是疏松多孔的Fes层。对影响碳钢钝化的因素也进行了研究。 根据碳钢在亚铵法蒸煮时的腐蚀特性,在纸厂现场试验了控制蒸煮液pH、设置防滑钉和快速升温等三种简易的防腐蚀措施,使用这些方法可使蒸球腐蚀率降到0.2mm/y以下。     

Corrosion mechanisms of steel concrete moulds in contact with a demoulding agent studied by EIS and XPS

The behaviour of E24 mild steel was studied by XPS analysis and electrochemical impedance spectroscopy (EIS) in a filtered solution of cement (pH 13), and an alkyl N-aminodiphosphonate aqueous solution called Aquadem^® (7?pH?13). XPS results showed that the corrosion products developed in both media consisted of Fe₂O₃, covered by a very thin layer of goethite. The thickness of this oxide layer was estimated to be 3 nm. XPS analysis also demonstrated the adsorption of Aquadem^® on the outer layer of FeOOH for pH lower than the zero charge pH of goethite (7.55). From XPS and EIS results, physical models of the E24 steel/electrolyte interface are proposed as a function of pH. For 11?pH?13, the steel is covered by a passive film, while for pH?10, pitting corrosion takes place. At pH 7, an additional mass transport phenomenon must be taken into account. The fitting procedure provided values for several physical parameters (electrolyte resistance, passive film resistance), from which the film capacitance and the dielectric constant of the oxide layer were calculated.