An investigation on the role of texture and surface morphology in the corrosion resistance of zinc electrodeposits

It has been shown in the literature that texture plays a major role in the corrosion resistance of zinc electrodeposits. This is because the grain dissolution rate depends on its orientation. In this research, the corrosion behavior of zinc electrodeposited coatings was investigated. It was observed that the corrosion resistance of zinc electrodeposits is related to the crystallographic planes exposed to aggressive solution, and not only the planes of texture components. The findings highlight the role of surface morphology of the coatings in exchange current density of water reduction and its subsequent effect on corrosion resistance.     

Enhancing the localised corrosion resistance of 316L stainless steel via FBR-CVD chromising treatment

The resistance of stainless steels to localised corrosion can be adversely affected by environmental and metallurgical heterogeneities existed in complex industrial infrastructures such as seawater desalination plants exposed to aggressive evnironments. It is therefore critical to enhance the localised corrosion resistance and understand the corrosion behaviour of stainless steels in complex and aggressive industrial environmental conditions. In this work, the localised corrosion resistance of chromised stainless steel 316L (SS316L) in simulated seawater desalination systems has been investigated by electrochemical and surface analytical techniques. It has been found that chromising processes have improved the localised corrosion resistance of SS316L by reducing its susceptibility to pitting, crevice, and welding zone corrosion in simulated seawater desalination environments. This increased corrosion resistance has been explained by electrochemical polarisation studies and surface analysis showing that the chromising treatment at 1050°C resulted in a continuous and stable chromium-enriched layer on the SS316L surface.     

Comparative effect of grain size and texture on the corrosion behaviour of commercially pure titanium processed by equal channel angular pressing

The effect of grain size and texture on the corrosion properties of commercially pure titanium was investigated. Equal channel angular pressing (ECAP) was used to produce different grain size and various crystallographic orientations. Electrochemical impedance spectroscopy was employed to measure the corresponding surfaces’ general corrosion resistance. Samples with the (0 0 0 2) planes parallel to the surface were found to offer the highest corrosion resistance, regardless of their grain size.     

The Effect of Surface Patterning on Corrosion Resistance of Biomedical Devices

In this study, two styles of surface topographies have been created on stainless steel wires to test their corrosion resistance as simulated implanted biomedical devices. Grade 316 LVM stainless steel wire was initially polished to G1500 surface finish before treatment to produce the two different topographies: 1. Unidirectional roughness was created using SiC papers and 2. Various patterns were created with specific hole diameter and inter-hole spacing using focused ion beam (FIB). In order to simulate the environment of implanted biomedical devices, a three-electrode electrochemical cell with 0.9% (by mass) NaCl solution has been used to test the corrosion resistance of the samples by potentiodynamic polarization test method. SEM and EDS analyzed the appearance and chemical composition of different elements including oxygen on the surface. The potential of stable pitting, time related to the initiation of the stable pitting, and the highest corrosion current associated with stable pitting have been compared for samples with the two styles of topography. It was found that surfaces with patterns have a relatively higher pitting potential and it takes longer time to initiate stable pitting than the surface without any patterns.     

Pitting corrosion behaviour of PM austenitic stainless steels sintered in nitrogen-hydrogen atmosphere

PM 304L and 316L stainless steel have been compacted at 400, 600 and 800 MPa and sintered in vacuum and in nitrogen-hydrogen atmosphere. Postsintered heat treatments (annealing solution and ageing at 375, 675 and 875 °C) have been applied. Pitting corrosion resistance has been studied using anodic polarization measurements and the ferric chloride test. Anodic polarization curves reveal that densities and atmospheres are relevant on anodic behaviour. Pitting resistance is higher for PM 316L and for higher densities and vacuum as sintered atmosphere. Ageing heat treatments at medium and high temperatures are detrimental to passivity although susceptibility to pitting corrosion barely changes. But heat treatments at 375 °C even show certain improvement in pitting corrosion resistance. The results were correlated to the presence of precipitates and mainly to the lamellar constituent which appears in some samples sintered in nitrogen-hydrogen atmosphere. The role of nitrogen on the samples sintered under nitrogen-hydrogen atmosphere and its relation to the microstructural features was described.     

Corrosion behaviour of Lotus-type porous high nitrogen nickel-free stainless steels

Corrosion behaviour of three austenitic Lotus-type porous high nitrogen Ni-free stainless steels exposed to an acidic chloride solution has been investigated by electrochemical tests and weight loss measurements. Polarization resistance indicates that the corrosion rate of Lotus-type porous high nitrogen Ni-free stainless steels is an order of magnitude lower than that of Lotus-type porous 316L stainless steel in acidic environment. The localised corrosion resistance of the investigated high nitrogen Ni-free stainless steels, measured as pitting potential, E_b, also resulted to be higher than that of type 316L stainless steel. The influences of porous structure, surface finish and nitrogen addition on the corrosion behaviour were discussed.     

Crystallographic pitting in magnesium single crystals

Abstract

The corrosion behaviour of three low index planes of an hcp magnesium (Mg) single crystal was investigated in 10^?2M NaCl/10^?4M dichromate solution. The Mg (0001) surface exhibited pitting corrosion susceptibility at the open circuit potential. However, the (1010), and (1120) surfaces were passive at open circuit and pitting only initiated at potentials slightly anodic to their open circuit potentials. The onset of stable dissolution in the three surfaces was marked by the formation and propagation of corrosion filaments. For the three surfaces investigated, pit shape was non-geometric, however, pit propagation was generally found to occur along preferential crystallographic directions. An analysis of the preferred crystallographic directions is presented.     

Corrosion behaviour of an Fe3Al-type intermetallic in a chloride containing solution

The corrosion behaviour of an Fe₃Al-base intermetallic compound with different crystal structures in a chloride containing solution has been investigated. The corrosion current densities of this intermetallic were independent of the material crystal structure showing a passive state stable with time. These corrosion rates were of the same order of magnitude as for 316L stainless steel. The pitting corrosion resistance evaluated by means of cyclic anodic polarization curves was high for all different states. Amongst the different crystal structures of this intermetallic alloy, the two ordered states present the lowest pitting probability. This Fe₃Al intermetallic shows higher pitting corrosion resistance than the 316L stainless steel but its capacity for repassivation is lower. A damaging factor of influence on the pitting corrosion behaviour is the presence of non-metallic inclusions on the surface which reduce the pitting corrosion resistance by almost a half.     

The effect of annealing on the corrosion behaviour of 444 stainless steel for drinking water applications

In this study, the corrosion behaviour of annealed and not annealed AISI 444 ferritic stainless steel in tap water with and without addition of selected concentrations of chloride ions was investigated. Cyclic potentiodynamic macro (large area) and micro (small area) polarization measurements (CPP), salt spray test, SEM and EDS analysis were employed to evaluate the pitting and crevice corrosion susceptibility of annealed and not annealed AISI 444. The results obtained indicate that annealing does not improve the resistance to pitting and crevice corrosion. Moreover, micro CPP indicates local susceptibility to pitting on both annealed and not annealed materials; such susceptibility was not evident from macropolarization tests.     

Investigation on Pitting Corrosion of Nickel-Free and Manganese-Alloyed High-Nitrogen Stainless Steels

Pitting corrosion behavior of three kinds of nickel-free and manganese-alloyed high-nitrogen (N) stainless steels (HNSSs) was investigated using electrochemical and immersion testing methods. Type 316L stainless steel (316L SS) was also included for comparison purpose. Both solution-annealed and sensitization-treated steels were examined. The solution-annealed HNSSs showed much better resistance to pitting corrosion than the 316L SS in both neutral and acidic sodium chloride solutions. The addition of molybdenum (Mo) had no further improvement on the pitting corrosion resistance of the solution-annealed HNSSs. The sensitization treatment resulted in significant degradation of the pitting corrosion resistance of the HNSSs, but not for the 316L SS. Typical large size of corrosion pits was observed on the surface of solution-annealed 316L SS, while small and dispersed corrosion pits on the surfaces of solution-annealed HNSSs. The sensitization-treated HNSSs suffered very severe pitting corrosion, accompanying the intergranular attack. The addition of Mo significantly improved the resistance of the sensitization-treated HNSSs to pitting corrosion, particularly in acidic solution. The good resistance of the solution-annealed HNSSs to pitting corrosion could be attributed to the passive film contributed by N, Cr, and Mo. The sensitization treatment degraded the passive film by decreasing anti-corrosion elements and Cr-bearing oxides in the passive film.     

Eis and XPS study of surface modification of 316LVM stainless steel after passivation

The effects of surface finish, nitric acid passivation and ageing in air on corrosion resistance of 316LVM stainless steel in 0.5% H₂SO₄ have been investigated by EIS, potentiodynamic polarization measurements and XPS. The results indicate that a smoother surface exhibits to a higher corrosion resistance. The effectiveness of the passivation treatment strongly depends on nitric acid concentration, passivation time and temperature. The passivation treatment significantly increases the corrosion resistance due to a high Cr content in the passive film and increased film thickness. Ageing after passivation increases the corrosion resistance whereas ageing before passivation has little effect.     

Cl–对冷变形316L奥氏体不锈钢在H2S环境下应力腐蚀的影响

目的研究H2S环境下不同Cl^-浓度对冷变形316L奥氏体不锈钢应力腐蚀行为的影响,探究Cl^-造成影响的原因,为不锈钢安全服役提供理论数据。方法采用力学方法研究了冷变形316L奥氏体不锈钢的力学行为,通过计算延伸率损失表征材料的应力腐蚀敏感性,通过电化学手段表征了点蚀电位。最后为了研究点蚀与基体中氢含量的关系,进行了扩散氢含量的测试,通过测量试样的扩散氢含量,进一步理解应力腐蚀行为。结果随着Cl^-浓度的增加,316L奥氏体不锈钢的延伸率损失逐渐增大,应力腐蚀敏感性增强。断口形貌从杯状的等轴韧窝转变为解理型脆性断裂。动电位极化测试表明,Cl^-浓度的增加,点蚀电位逐渐降低,直至–0.0228V,试样更容易发生点蚀。扩散氢含量的测量进一步显示了点蚀坑的存在促进了氢进入到金属内部。结论 Cl^-对316L奥氏体不锈钢在H2S环境中的应力腐蚀行为有重要影响,随着Cl^-浓度的增加,应力腐蚀敏感性增强,结合点蚀电位的测量结果,可能是由于Cl^-破坏金属表面的钝化膜,产生点蚀坑,裂纹形核并扩展,同时点蚀坑还促进了氢进入金属内部,应力腐蚀敏感性增强。     

Corrosion of aluminium,stainless steels and AISI 680 nickel alloy in nitrogen‐based fuels

Nitrogen‐based compounds can potentially be used as alternative non‐carbon or low‐carbon fuels. Nevertheless, the corrosion of construction materials at high temperatures and pressures in the presence of such fuel has not been reported yet. This work is focused on the corrosion of AISI Al 6061, 1005 carbon steel (CS), 304, 316L, 310 austenitic stainless steels (SS) and 680 nickel alloy in highly concentrated water solution of ammonium nitrate and urea (ANU). The corrosion at 50 °C and ambient pressure and at 350 °C and 20 bar was investigated to simulate storage and working conditions. Sodium chloride was added to the fuel (0–5 wt%) to simulate industrial fertilizers and accelerated corrosion environment. Heavy corrosion of CS was observed in ANU solution at 50 °C, while Al 6061, 304 and 316L SS showed high resistance both to uniform and pitting corrosion in ANU containing 1% of sodium chloride. Addition of 5% sodium chloride caused pitting of Al 6061 but had no influence on the corrosion of SS. Tests in ANU at 350 °C and 20 bar showed pitting on SS 304 and 316L and 680 nickel alloy. The highest corrosion resistance was found for SS 310 due to formation of stable oxide film on its surface.     

激光电子散斑干涉技术监测奥氏体不锈钢在NaCl溶液中的点蚀敏感性

用动电位极化和电化学阻抗等方法检测1Cr18Ni9Ti、304和316三种奥氏体不锈钢在3.5%NaCl溶液中的点蚀敏感性;用恒电位下的计时电流法结合激光电子散斑干涉技术（ESPI）实时监测这三种材料在3.5%NaCl溶液中阳极极化过程的表面动态变化及点蚀感应时间(τ)。结果表明,当电极表面发生点蚀时,激光电子散斑干涉图上会出现由点蚀产物扩散引起的亮斑。1Cr18Ni9Ti和 304不锈钢的τ值分别是1 s和9 s,316不锈钢的τ值大于50 s。由此可以判断1Cr18Ni9Ti的点蚀敏感性最大,304居中,316的点蚀敏感性最小。此结果与动电位极化和电化学阻抗等电化学方法得出的结果一致。激光电子散斑干涉技术可以做为一种实验室方法监测金属早期点蚀敏感性。     

The Effect of Texture on the Corrosion Behavior of AZ31?Mg Alloy

Magnesium (Mg) grains show anisotropic corrosion behavior, which implies that the single-phase, hot-rolled Mg alloy AZ31 sheet, if highly textured, will have different corrosion performance depending on its crystallographic orientation of the grains. Its rolling surface, dominated by (0001) basal crystallographic planes, is more corrosion resistant than its cross-section surface, which is mainly composed of $ \{ 10\overline{1} 0\} $ and $ \{ 11\overline{2} 0\} $ prismatic crystallographic planes. Furthermore, grain refinement by hot rolling is beneficial to the overall corrosion resistance of AZ31 because of the dissolution of AlMn(Fe) intermetallic precipitates in the alloy. Surface compressive deformation machining can lead to refined grains and an expected preferred grain orientation, thus improving the corrosion resistance of AZ31 alloy.     

Corrosion characteristics of nickel, copper, and stainless steel in a Lewis neutral chloroaluminate ionic liquid

Corrosion of nickel, copper, and 316 stainless steel in aluminum chloride/1-ethyl-3-methylimidazolium chloride ionic liquid (IL) is investigated by means of electrochemical techniques. SEM analyses are performed to examine the reaction mechanisms. While Ni shows good stability, Cu has high corrosion susceptibility in this IL. For 316 steel, pitting corrosion occurs at a lower potential than that of passivation. In the non-aqueous, low-oxygen, and high-ion-containing IL, the material corrosion properties are totally different from those found in conventional environments. Since ILs have found increasing potential in diverse applications, new corrosion prevention strategies are needed to overcome the IL-derived material corrosion problems.     

脉冲偏压对316L不锈钢表面类金刚石薄膜腐蚀行为影响EI北大核心CSCD

为了提高不锈钢的耐局部腐蚀性能,采用等离子体增强化学气相沉积(Plasma-enhanced chemical vapor deposition,PECVD)技术,在316L不锈钢表面制备含氢类金刚石(Diamond-like carbon,DLC)薄膜,研究不同脉冲偏压对薄膜的杂化结构及腐蚀行为的影响,并对相关影响机制进行讨论。结果表明,脉冲偏压主要影响316L不锈钢表面DLC薄膜的杂化结构及微观形貌,并最终影响其腐蚀行为。随着脉冲偏压的增加,等离子体电离程度增大,沉积过程中的热峰效应和溅射效应增强,DLC薄膜中的氢含量减少,降低了薄膜局部腐蚀敏感性,薄膜点蚀坑数量减少。但同时薄膜中sp^(2)杂化结构的相对含量会随脉冲偏压升高而增加,导致薄膜腐蚀速率加快,点蚀坑半径增大。随着偏压从1.4 kV增加到2.6 kV,316L不锈钢的年腐蚀速率由9.33 nm/y增大到62.4 nm/y。脉冲偏压为1.4 kV时,虽然年腐蚀速率最低,但薄膜最易发生点蚀,其长期服役寿命较差;而偏压为2.6 kV时,等离子体能量过高,薄膜被过度刻蚀,导致其缺陷增多,耐蚀性变差。在研究范围内,脉冲偏压为2200 V时,DLC薄膜具有较高的耐点蚀能力和较低的年腐蚀速率,表现出最佳的综合耐蚀性能。     

Effect of Alloying Tin on the Corrosion Characteristics of Austenitic Stainless Steel in Sulfuric Acid and Sodium Chloride Solutions

The effect of tin on general and pitting corrosion behaviors of the austenitic stainless steel in sulfuric acid and sodium chloride solutions was investigated by potentiostatic critical pitting temperature, cyclic potentiodynamic polarization, electrochemical impedance spectroscopy, and scanning electron microscopy. The results showed that there is an optimal tin addition which is around(0.062–0.1) wt%, and the general corrosion resistance of B316 LX with 0.08 wt% tin addition in boiling H2SO4 increased remarkably with a corrosion rate of an order of magnitude lower than that of 316 L.Hydrolyzation of tin ions induces more metastable pit occurrence on the material surface. However, the pitting resistance of B316 LX increases because tin oxides improve the density and uniformity of the passive film, and hydroxide and oxide of tin inhabit the process of pit growing. The effect of tin on pitting corrosion process is illustrated schematically.     

Characterization of Localized Corrosion in an Al-Cu-Li Alloy

Corrosion behaviors of recently developed 2A97-T6 aluminum-copper-lithium alloy in sodium chloride solution are investigated using scanning electron and transmission electron microscopies in conjunction with electron backscatter diffraction. It has been found that corrosion product rings were established on the alloy surface as early as 5 min during immersion in sodium chloride solution. Meanwhile, hydrogen continuously evolved from within the rings. Pitting corrosion is evident with crystallographic dependant corrosion channel facets mainly parallel to {100} planes. Non-uniform distribution of misorientation in the 2A97 aluminum alloy results in a portion of grains of relatively high stored energy. Such grains were preferentially attacked, serving as local anodes, during the development of crystallographic pitting.     

Pitting corrosion behaviour of austenitic stainless steels with Cu and Sn additions

The influence of Cu and Sn on the pitting corrosion resistance of AISI 304 and 316 stainless steels in chloride-containing media has been investigated. The corrosion behaviour was evaluated by cyclic polarization, potentiostatic CPT measurements and electrochemical impedance spectroscopy in 3.5 wt% NaCl. The corrosion resistance was also studied in FeCl₃ under Standard ASTM G-48. According to the results, Cu addition favours pit nucleation but inhibits its growth, whereas Sn exerts the opposite effect, favouring pit growth and inhibiting its nucleation. Studies by SEM, X-ray mapping and EDS analysis showed Cu-, Cl- and O-rich corrosion products that reduce the extent of corrosion damage.