Mn-Cu低合金钢在模拟海岸大气条件下的锈蚀演化规律

利用干湿循环加速腐蚀实验方法研究了Mn-Cu低合金钢在模拟海岸大气条件下的锈蚀演化规律.结果表明,在腐蚀初期锈蚀速度随干湿循环次数的增加而增大,随后转为随干湿循环次数的增加而降低.带锈层的Mn-Cu低合金钢的电化学极化行为表明,干湿循环下的腐蚀产物促进阴极过程,抑制阳极过程.在干湿循环加速腐蚀进程中Mn-Cu低合金钢表面铁锈的化学组成、结构变化表现为在锈蚀初期α-FeOOH含量较低,锈层疏松,锈蚀速度呈随干湿循环次数增加而上升趋势;后期随α-FeOOH含量的增加和锈层变得更加致密,腐蚀速度转变为随干湿循环次数增加而下降.锈蚀演化过程中,腐蚀速度和极化行为随干湿交替次数的演化与相应的锈层组成、结构形貌的变化有对应关系.     

低碳钢带锈电极的腐蚀行为

研究了一种低碳钢在干湿交替腐蚀加速实验条件下的锈蚀速度变化.结果表明：在初期，锈蚀速度随干湿交替次数的增加而增大，随后转为随干湿交替次数的增加而降低；低碳钢锈蚀速度的转变与铁锈组成的变化有关，γ-FeOOH和Fe3O4的形成是腐蚀速度出现转化的因素之一.带锈低碳钢的电化学极化行为表明 ，干湿交替初期的腐蚀产物对阴极和阳极过程都有促进作用，在后期表现为对阳极过程抑制，而对阴极过程促进.同时，提出了一种描述低碳钢大气腐蚀行为的流程图.     

耐候钢在含MgCl2介质的干湿环境下的腐蚀行为

通过以0.3%MgCl2溶液为介质的浸渍干湿循环加速腐蚀试验,研究了Corten-A耐候钢在干/湿环境下的腐蚀行为.扫描电镜(SEM)和能量色散X射线谱(EDX)观察分析了各腐蚀循环下的腐蚀形貌及Cl、Mg元素含量的变化.结果表明Corten-A钢的腐蚀失重与循环次数呈线性关系.腐蚀产物中的晶体相初期主要是β-FeOOH,后期主要是γ-FeOOH和少量的ε-Fe2O3.电化学测试表明铁锈的还原反应加速了阴极反应;锈层的电容值比较大,说明锈层的结构比较疏松,不具保护性.     

桥梁耐候钢在含Cl~-离子环境中的腐蚀行为

选择3种Ni含量为3.5%的桥梁钢,采用干湿周浸加速腐蚀实验模拟海洋大气环境下桥梁钢的耐腐蚀性能变化,并利用金相显微镜、XRD和SEM等分析了不同Mn和Cu含量桥梁耐候钢组织以及其腐蚀不同时间的腐蚀形貌和锈层特征.结果表明:桥梁耐候钢的组织由准多边形铁素体、针状铁素体和粒状贝氏体组成;随着Mn含量的增加,钢的耐蚀性能增加;Ni和Mn在锈层中均匀分布,Cu在锈层的缝隙或孔洞等缺陷处富集.锈层主要由Fe_3O_4,γFeOOH和α-FeOOH组成,腐蚀不同时间后的试样锈层组成相有所不同;γ-FeOOH和α-FeOOH与钢的腐蚀速率密切相关;增加Mn含量可以促进γ-FeOOH和α-FeOOH的生成,同时抑制γFeOOH和αFeOOH的晶粒长大.     

Q235钢在海水淡化一级反渗透产水中的腐蚀行为

采用旋转挂片和SEM, EDS及IR分析研究Q235钢在海水淡化一级反渗透产水中(RO)的腐蚀速度和腐蚀产物变化规律,并利用动电位扫描、电化学阻抗法研究腐蚀过程及腐蚀反应控制步骤。结果表明,Q235钢在海水淡化一级反渗透产水中腐蚀速度在48 h内迅速增大至1.4 mm/a,其后保持稳定。锈层初期为γ-FeOOH薄层,随时间延长逐渐转为由Fe₃O₄构成的内锈层及由γ-FeOOH和α-FeOOH构成的外锈层。腐蚀过程受阴极控制,初期腐蚀阻力达到最大,其后由于大量γ-FeOOH在酸性条件下极易转化为对腐蚀反应没有阻滞作用的Fe₃O₄,腐蚀阻力迅速减小,腐蚀速度迅速增大,当Q235钢表面γ-FeOOH生成和转化达到平衡后,腐蚀阻力保持稳定,腐蚀速度也不再发生变化。     

Cu、Mn的协同作用对低合金钢在模拟海洋大气环境中腐蚀的影响

    用增重法、扫描电镜、X射线衍射、电子探针和X射线光电子能谱等手段研究了在模拟海洋大气干湿交替环境下16Mn钢和Cu-Mn耐候钢的腐蚀行为及Cu、Mn共添加对低合金钢腐蚀行为的影响.结果表明：Cu-Mn耐候钢的腐蚀速率低于16Mn钢,其锈层更致密;两种钢的铁锈均由Fe₃O₄,α-FeOOH,β-FeOOH,γ-FeOOH和大量无定形相组成;添加Cu使Fe₃O₄含量增加,添加Mn使γ-FeOOH含量减少;Cu在Cu-Mn耐候钢锈层中以CuFeO₂存在;Mn在两种钢锈蚀初期以MnO存在,后期为Mn₃O₄.Cu、Mn的协同作用使Cu-Mn耐候钢抗大气腐蚀性能优于16Mn钢.     

新型复配阻锈剂在混凝土模拟液和试块中对钢筋锈蚀的抑制

利用半电池腐蚀电位、线性极化和电化学交流阻抗技术,分别在混凝土模拟液和干湿循环加速腐蚀混凝土试块中,研究了新型复配有机阻锈剂(IMC-16)对钢筋锈蚀行为的影响,并将其与常规Ca(NO2)2阻锈性能相对比。结果表明,无论在混凝土模拟液中还是在混凝土试块中,空白条件下,随实验时间延长钢筋电极腐蚀电位不断下降,腐蚀电流密度迅速升高,表明在Cl-侵蚀性作用下钢筋表面钝性遭到破坏,并发生严重局部腐蚀;而添加IMC-16阻锈剂后,钢筋电极腐蚀电位升高,阻抗模值增大,腐蚀电流密度与双电层电容显著下降,表明钢筋的锈蚀得到很好的控制。复配阻锈剂对Cl-诱导的钢筋局部腐蚀具有优良的抑制效果,并可有效延缓钢筋的起始锈蚀时间。干湿循环实验结果进一步表明,实验初期Ca(NO2)2虽可较好抑制钢筋的锈蚀,但其后期阻锈性能却明显下降;而复配阻锈剂在实验初期阻锈性能虽不明显,但相同使用浓度下,其后期阻锈效果及稳定性却明显优于Ca(NO2)2。     

低碳钢Q235在模拟酸雨大气腐蚀条件下的电化学阻抗谱监测

使用干湿交替方法模拟酸雨大气腐蚀条件,并利用电化学阻抗谱(EIS)技术对腐蚀过程进行实时监测,对低碳钢Q235在模拟酸雨大气环境下的腐蚀行为进行研究,着重探讨阴极还原反应的演化特征.结果表明,低碳钢Q235的阴极反应为氧的还原反应和锈层(腐蚀产物)的还原反应并行.随着干湿交替循环次数的增加,氧还原反应的活性逐渐减弱,最后几乎完全消失;而锈层还原反应的活性逐渐增虽,并取代氧还原反应成为主要的阴极反应.在同一个干湿交替周期内,腐蚀速率随着液膜厚度的减小呈现先增加,然后迅速降低的规律,这是由于液膜厚度对腐蚀反应同时存在2种效果相反的作用所致.     

紫外光下锈层光电催化性能对碳钢腐蚀行为的影响

采用电化学阻抗方法,研究了在紫外光辐照下带锈层碳钢的腐蚀电化学行为,探究了紫外光所致的锈层光电催化效应及其对碳钢腐蚀的影响。结果表明,紫外光辐照能引发锈层光电催化反应,促使电极的腐蚀加速;锈层由γ-FeOOH外锈层和Fe2O3与Fe3O4内锈层组成,但它们在光电催化中的作用仍待研究。长期腐蚀过程的电化学阻抗谱图表明,带锈低碳钢电极的腐蚀比裸电极的大,随时间延长锈层逐步增厚引起光电催化效应强度增大,促进基体电极腐蚀程度增加;锈层积累42 d达到一定厚度时,随时间延长锈层促进基体电极腐蚀程度减缓,引起光电催化效应的强度会趋于一个稳定值。     

Ni含量对铜时效易焊接钢在模拟热带海洋大气环境下的腐蚀行为影响

通过室内干湿交替加速实验模拟热带海洋大气环境，研究了2.5Ni、2.0Ni、1.5Ni不同Ni含量的铜时效易焊接钢的腐蚀行为。采用失重法表征了实验钢的耐蚀性，采用扫描电镜(SEM)、X射线衍射(XRD)、电子探针(EPMA)和电化学测试等方法对锈层的保护性能进行分析。结果表明，在热带海洋大气环境下，3种实验钢的腐蚀速率均先增加后降低随后保持稳定，Ni含量越高腐蚀速率越低，2.5Ni实验钢腐蚀速率较1.5Ni实验钢降低25%。锈层分析表明，Ni和Cu主要富集在锈层内部，钢中添加Ni会在锈层内部生成NiFe₂O₄，促进γ-FeOOH相向α-FeOOH转化，使得锈层更加致密，且Ni含量越高，效果越明显，锈层的保护性越好。随着Ni含量的增加，带锈试样的自腐蚀电位以及锈层电阻随之增加，锈层可以有效抑制阳极溶解以及带电粒子的转移。     

Corrosion behavior of steel under wet and dry cycles containing Cr ion

The corrosion behavior of mild steel has been investigated during the wet and dry cyclic transitions containing Cr³⁺ ion added as sulfate in order to gain a better understanding of the influence of Cr on the atmospheric corrosion of steels. The corrosion rate during drying is greatly suppressed by the existence of Cr³⁺ ion in the electrolyte covered with the surface. Lower corrosion rates are observed during drying even if the surface have been polarized to negative potentials below −200 mV_SHE during the wet corrosion conditions in which the surface-covered electrolyte contains Cr³⁺ ion. This corrosion behavior is identical to the case of Cr-containing steel for the wet and dry cyclic transitions without the addition of Cr³⁺ ion. The composition of rust layer after the wet and dry cyclic transitions is composed of α-FeOOH, γ-FeOOH and Fe_3−δO₄ for both cases of non-Cr³⁺ and Cr³⁺-containing condition, and no significant difference in the mass fraction of the above rust substances between two conditions is observed by means of Mössbauer spectroscopy. The only difference in the rust layer is that the rust formed under the wet and dry cyclic transitions containing Cr³⁺ ion contains a certain amount of Cr near the steel/rust interface. Those results suggest that the role of Cr during the wet and dry cyclic transitions is the inhibition of the rust reduction and the formation of Fe²⁺-state intermediate by the existence of Cr in the rust layer. This can lead to the inhibition of the oxygen reduction during drying.     

In situ observation of initial rust formation process on carbon steel under Na2SO4 and NaCl solution films with wet/dry cycles using synchrotron radiation X-rays

Atmospheric corrosion of steel proceeds under thin electrolyte film formed by rain and dew condensation followed by wet and dry cycles. It is said that rust layer formed on steel as a result of atmospheric corrosion strongly affects the corrosion behavior of steel. The effect of environmental corrosiveness on the formation process and structure of the rust layer is, however, not clear to date. In this study, in situ observation of the rusting process of a carbon steel covered with a thin film of Na₂SO₄ or NaCl solution was performed under a wet/dry repeating condition by X-ray diffraction spectroscopy with white X-rays obtained from synchrotron radiation. The present in situ experiments successfully detected initial process of the rust formation. In the early cycles, the rust constituents were not well crystallized yet, but the presence of Fe(OH)₂ and Fe(OH)₃ was confirmed. In the subsequent cycles, two different solutions resulted in difference in preferential phase of the rust constituents. α-FeOOH was preferentially formed in the case of the Na₂SO₄ solution film, whereas β-FeOOH appeared only under the NaCl solution film.     

周期干湿浸条件下P265GH钢和Q235钢的大气腐蚀行为简

以NaCl+NaHSO3为腐蚀介质,通过浸渍干湿复合循环实验及腐蚀失重分析,并利用SEM,XRD和FTIR技术,研究了Q235碳钢和P265GH低合金钢的大气腐蚀行为。结果表明,两种钢的腐蚀遵从相同的动力学规律,腐蚀产物中均存在大量致密的α-FeOOH和非晶态δ-FeOOH,锈层具有很好的保护性,使得腐蚀速率降低。实验开始阶段两种钢的腐蚀量基本相同,但随着腐蚀的进行两者差距增大,P265GH低合金钢较Q235碳钢的失重小、锈层致密、耐腐蚀性好。     

Control of Fe(O,OH)6 nano-network structures of rust for high atmospheric-corrosion resistance

A new-type of weathering steel containing 3.0 mass% Ni and 0.4 mass% Cu (“advanced weathering steel”) exhibits good atmospheric-corrosion resistance in an atmosphere containing relatively high air-born salinity. Here, we show that the high performance was successfully achieved by controlling Fe(O,OH)₆ nano-network structures of rust formed on their surfaces. A novel technique using synchrotron radiation has been developed for the in situ observation of rust-formation during wet-dry cycles. It has been revealed that the evolution of Fe(O,OH)₆ nano-network structures of rust formed on the advanced weathering steel was more unique than those of conventional weathering steel and mild steel. At an early stage of reaction, Fe₂NiO₄ and CuO phases precipitate, which provide sites for the nucleation of the Fe(O,OH)₆ nano-network resulting in the formation of rust composed of fine and dense-packed grains. The existence of Fe₂NiO₄ in the nano-network changes the ion-exchanging properties of rust from anion to cation selective. Then, the rust on the advanced weathering steel “breathes out” chloride ions from the rust/steel interface, and protects steel for more than a century by reducing the life cycle maintenance cost in an environment-friendly manner.     

Electrochemical methods study on corrosion of 5% Al–Zn alloy‐coated steel under thin electrolyte layers

The corrosion behavior of a 5% Al–Zn alloy (GF) coated steel was investigated under cyclic wet–dry condition using electrochemical techniques. The wet–dry cycle was conducted by exposure to alternate condition of 1 h immersion in seawater and 7 h drying at ambient temperature. The polarization resistance, R_p of the coating was monitored during the wet–dry cycles by two points AC impedance method and the corrosion potential, E_corr was measured only when the coating was immersed in seawater. Simultaneously, the electrochemical impedance spectroscopy (EIS) of the coating was obtained after it was immersed in different cycles of wet–dry condition. The results obtained by two points AC impedance method had good agreement with those achieved from EIS technique, which proved that the two points AC impedance method was correct and an effective method for atmospheric corrosion study. The monitoring results indicated that the corrosion rate of GF coating firstly increased, then decreased slowly with time, and at last reached a relative steady state with local corrosion under the cyclic wet–dry alternate condition.     

Effects of NH4 +, Na+, and Mg2+ ions on the corrosion behavior of galvanized steel in wet–dry cyclic conditions

The effect of cations on the corrosion of galvanized steel (GS) is scarcely reported. In this study, a wet–dry cyclic test was conducted to study NH₄ ⁺, Na⁺, and Mg²⁺ cation effect on the corrosion behavior of GS available in Nepal. Fourteen wet–dry cycles (18 h wet and 6 h dry) were performed by exposing samples at 298 K with a relative humidity of 90% in a wet cycle and 50% in a dry cycle for 14 days. The cations strongly affect the corrosion rate of the GS sample estimated by weight loss and potentiodynamic polarization. The potentiodynamic polarization curves showed the inhibition of cathodic and anodic reactions by Mg²⁺ ion, while the NH₄ ⁺ ion only changed the cathodic reaction. Mg²⁺ ion was found to shift the corrosion potential to noble values compared with NH₄ ⁺ and Na⁺ ions. A compact and thin corrosion products layer was developed in Mg²⁺ salt solution in contrast to a thick and porous corrosion products layer in NH₄ ⁺ and Na⁺ salt solutions. Red rust due to corrosion of underlying steel appeared in the presence of NH₄ ⁺ and Na⁺ salt solutions. Finally, the weight loss data revealed that the corrosivity of cations for GS decreased in the order Na⁺ > NH₄ ⁺ > Mg²⁺.     

Corrosion behavior of carbon steel coated with a zinc-rich paint containing metallic compounds under wet and dry cyclic conditions

The corrosion behavior of carbon steel coated with a zinc-rich paint containing two metallic compounds, Al₂(SO₄)₃ and CaO, as anticorrosive additives was examined under wet and dry cyclic corrosion test conditions. The zinc-rich paint coating without the two metallic compounds formed a white corrosion product and red iron rust on the surface after the corrosion test, whereas the coating with the metallic compounds showed reduced surface corrosion products. The corrosion current density of the painted steel substrate decreased drastically due to the incorporation of metallic compounds in the paint. The zinc-rich paint coating modified with the metallic compounds contained dispersed simonkolleite (Zn₅(OH)₈Cl₂·H₂O) phase and possibly very fine CaSO₄ particles, which remarkably improved the protectiveness of the zinc-rich paint coating.     

The influence of copper upon the atmospheric corrosion of iron

The atmospheric corrosion of pure iron and the binary alloy Fe-0.5Cu has been analyzed by a simultaneous measurement of the anodic current density of the metal dissolution and the cathodic current density of the O₂ reduction reaction during several wet/dry cycles using a magnetic and a gas volumetric technique, respectively. The results show three typical stages of the atmospheric corrosion: stage 1 (wetting of a dry surface): rapid corrosion with rust reduction as cathodic process; stage 2 (wet surface): slow corrosion with O₂ reduction as cathodic process; and stage 3 (drying out of the surface): very rapid corrosion with O₂ reduction as the cathodic process during critical wetting of the surface. The effect of copper is restricted to stage 3, where the corrosion rate is much smaller for the Fe-0.5Cu alloy than for pure iron. Two models are discussed to explain these results.     

Ex-situ and in-situ X-ray diffractions of corrosion products freshly formed on the surface of an iron-silicon alloy

Ex-situ X-ray diffraction measurements of a small amount of samples extracted from wet corrosion products freshly formed on a pure iron and iron-2 mass% silicon surfaces have been conducted using synchrotron radiation for clarifying the formation process of corrosion products. The results showed that γ-FeOOH was formed on the outer side of wet corrosion products formed on the surface of the pure iron by sodium chloride solution, while γ-FeOOH, α-FeOOH, Fe₃O₄, and green rusts were formed on the inner side. On the other hand, in comparison to the case of the pure iron, a significant formation of β-FeOOH was observed in the iron-silicon alloy. Influences of silicon alloying on corrosion products formed by aqueous solution containing sulfate ions were also observed. Furthermore, in-situ diffraction measurements by a conventional X-ray source were conducted for analyzing corrosion products formed on the pure iron and iron-silicon alloy surfaces by cyclic exposure to wet and dry atmospheres. The results obtained by the in-situ diffraction and ex-situ diffraction measurements on the corrosion products were consistent.