Nanostructure and energy properties of the stainless steel <Emphasis Type="Italic">X18N10T</Emphasis> surface studied by scanning tunneling microscopy and scanning tunneling spectroscopy. 2. Measurements at different potentials in HCl and H<Subscript>2</Subscript>SO<Subscript>4</Subscript> solutions

Stainless steel Kh18N10T is studied by electrochemical scanning tunneling microscopy (ESTM) and electrochemical scanning tunneling spectroscopy (ESTS) at the interface with solutions of 0.01 N HCl and 0.1 N H₂SO₄ at the controlled sample and tip potentials. The sample potential varied from ?0.46 to +1.14 V in 0.01 N HCl and from ?0.06 to +0.74 V (NHE) in 0.1 N H₂SO₄. It is shown that although in the studied acid solutions at the controlled potential the surface is smother than in air, this does not allow one to determine the extremal values of parameters α, β, and γ corresponding to individual properties of Fe, Cr, and Ni or their oxides. It is shown that compared to the steel nanorelief, the sample potential has a stronger effect on the electrophysical properties that determine the tunneling transfer of electrons.     

Magnetron sputtered Au-Pd-In alloys: microgravimetric and electrochemical characterisation in simulated physiological solutions

An electrochemical quartz crystal microbalance (EQCM) has been applied in corrosion sensing of magnetron sputtered Au-Pd-In alloy in simulated physiological solutions. The piezoelectric resonators were prepared by alloy deposition on quartz substrates by a DC magnetron-sputtering (MS) technique. X-ray photoelectron spectroscopy (XPS) analysis showed that the deposit composition was similar to that of the MS target, which was a commercially available casting alloy. X-ray diffraction indicated that the sputtered alloy has a crystalline structure. Measurements by using impedance spectroscopy and DC voltammetry showed some differences in electrochemical behaviour of both sputtered and cast alloy; however, these data did not indicate superior corrosion resistance of the sputtered specimen. Alloy corrosion has been studied by EQCM in three simulated physiological solutions: 0.9 N NaCl, 0.1 N NaCl+0.1 N lactic acid and artificial saliva. The EQCM indicated corrosion as increase in electrode mass, which was due to accumulation of corrosion products on the surface. The mass gain curves were similar in both neutral (pH 6) and acidic (pH 2.2) solutions, what implies dissolution of corrosion products in both media to be insignificant. XPS analysis showed that In₂O₃ was the main corrosion product on the surface. Corrosion current calculations from the mass curves were undertaken, which yielded the same corrosion rate assuming different oxides on the surface. The average corrosion rates in oxygenated 0.9 N NaCl and 0.1 N NaCl+0.1 N lactic acid solutions were similar and about twice as high as that in saliva.     

Kinetics of hydrogen evolution from acidic solutions on pressed micro graphite electrodes modified with carbon nanotubes. II. Impedance studies

The kinetics of hydrogen evolution on pressed micro graphite electrodes modified with multi-walled carbon nanotubes (MWCNTs) is studied in chloride environments with a constant ionic strength equal to unity with the use of impedance spectroscopy. The impedance of electrodes containing from 0.1 to 8 wt % MWCNTs in solutions of a general composition x M HCl + (1 − x) M NaCl at a currentless potential and at E = −0.6 V (N.H.S.) is interpreted as impedance of porous electrodes. The data obtained indicate the absence of diffusion limitations of the processes that proceed at a currentless potential and of the hydrogen evolution reaction. When the content of MWCNTs in a micro graphite electrode increases to 8 wt % at E = −0.6 V (N.H.S.), the increase in the contribution of the double layer capacitance and the adsorption capacitance to the Faraday impedance is the most pronounced, which means that MWCNTs promote a specific interaction of the electrolyte ions and atomic hydrogen with the surface of the cathodically polarized electrode.     

ESTM study of nanostructure and surface energetic properties of individual chromium and nickel

Individual chromium and nickel in air and at interfaces to 0.01 N HCl and 0.1 N H₂SO₄ solutions are studied with the use of electrochemical scanning tunneling microscopy (ESTM) and electrochemical scanning tunneling spectroscopy (ESTS) at the controlled potentials of the specimen and tip. The potential range of chromium specimens was 0.1 to 0.9 V in 0.01 N HCl and 0.3 to 1.1 V in 0.1 N H₂SO₄; the potential range of nickel was −0.01 to 0.64 V in 0.01 N HCl and 0.184 to 0.834 V (N.H.E.) in 0.1 N H₂SO₄. At the controlled potential, the surfaces in the studied acid solutions are smoother than in air. The potential of the specimen affects the electrophysical properties, which determine the electron tunneling transfer, more noticeably than the nanorelief of the metals. The obtained changes in the I _t,dZ spectra dependence on the distance in air on a field of 1 nm² at a step of 0.04 nm enabled us to estimate the effective barrier of tunneling K _ef between neighbor atoms, which is in good agreement with the known dependence of K _ef on the work function.     

Nanostructure and energy properties of the stainless steel X18N10T surface studied by scanning tunneling microscopy and scanning tunneling spectroscopy. 2. Measurements at different potentials in HCl and H2SO4 solutions

Stainless steel Kh18N10T is studied by electrochemical scanning tunneling microscopy (ESTM) and electrochemical scanning tunneling spectroscopy (ESTS) at the interface with solutions of 0.01 N HCl and 0.1 N H₂SO₄ at the controlled sample and tip potentials. The sample potential varied from −0.46 to +1.14 V in 0.01 N HCl and from −0.06 to +0.74 V (NHE) in 0.1 N H₂SO₄. It is shown that although in the studied acid solutions at the controlled potential the surface is smother than in air, this does not allow one to determine the extremal values of parameters α, β, and γ corresponding to individual properties of Fe, Cr, and Ni or their oxides. It is shown that compared to the steel nanorelief, the sample potential has a stronger effect on the electrophysical properties that determine the tunneling transfer of electrons. Original Russian Text ? Yu.M. Stryuchkova, E.V. Kasatkin, 2008, published in Fizikokhimiya Poverkhnosti i Zashchita Materialov, 2008, Vol. 44, No. 6, pp. 620–626.     

In situ ESTM and ESTS studies of the nanostructure and energetic properties of Fe-20% Cr-40% Ni and Fe-20% Cr-70% Ni alloy surfaces

Fe-20% Cr-40% Ni and Fe-20% Cr-70% Ni alloys are studied in air and in 0.01 N HCl and 0.1 N H₂SO₄ solutions at the controlled potentials of the specimen and needle using in situ techniques of electrochemical scanning tunneling microscopy (ESTM) and electrochemical scanning tunneling spectroscopy (ESTS). The changes in the potential of Fe-20% Cr-40% Ni alloy specimen fall in ranges of −0.3 to 1.1 V and 0–0.3 V (N.H.E.) in 0.01 N HCl and 0.1 N H₂SO₄, respectively, and the changes in the potential of Fe-20% Cr-70% Ni specimen, in ranges of 0.09–0.94 V and −0.1 to 0.5 V in 0.01 N HCl and 0.1 N H₂SO₄, respectively. Local spectral dependences of the tunnel current on the tunnel voltage are obtained and processed and the coefficients that characterize the local electrophysical properties of the surfaces are calculated on their basis. It is found that, in the studied acid solutions at the controlled potential, the surfaces are more energetically homogeneous than in air, where a substantially larger dispersion of the properties is observed. It is concluded that the energetic characteristics of separate surface sites of these alloys are determined on the atomic scale by the mutual effects of the neighboring atoms involved in its composition, i.e., by the matrix effect, which was discovered previously in the case of Kh18N10T stainless steel [1].     

铀在干燥氯化氢气氛中的腐蚀行为

研究了铀在干燥氯化氢－空气介质中的加速腐蚀情况,半进行了干燥空气氧化对照实验。研究表明：在干燥的含氯化氢－空气介质下铀的腐蚀速度与干燥空气介质下的氧化速度相比差别不大,但在不同阶段的速度趋势有显著的判别;在干燥空气介质中,铀表面的氧化主要是形成ＵＯ２,ＵＯ２＋ｘ;氯化物夹杂对腐蚀有显著的促进作用;氯化氢中的氢元素与轴作用产生氢化负,后者在氧和氯存在的条件下,反应生成氢气,氢气在金属／氧化物的缺陷区     

电化学氧化对碳纤维表面电化学性质的影响

碳纤维表面呈现化学惰性,缺乏活性官能团,限制了碳纤维作为电化学分析电极的应用.目前,许多手段被用于碳纤维的表面改性处理.采用电化学氧化方法,在磷酸溶液中对碳纤维进行了处理,并进行了红外光谱和循环伏安试验.结果发现:处理后碳纤维的表面接上了活性官能团,大量活性碳原子被剥离出来.在K4Fe(CN)6加KCl、FeSO4加HClO4两组混合溶液体系中的电化学响应明显改善,适合作为电化学分析电极.     

Detection of gaseous species during KCl-induced high-temperature corrosion by the means of CPFAAS and CI-APi-TOF

Two different analytical approaches—collinear photofragmentation and atomic absorption spectroscopy (CPFAAS) and chemical ionization atmospheric pressure interface time-of-flight mass spectrometer (CI-APi-TOF)—were applied to detect and identify the online gaseous KOH and HCl formed in the addressed high-temperature reactions. Samples of pure KCl, KCl+Cr, KCl+Fe, and KCl+316 L were studied at 550°C under dry and humid conditions with varying oxygen concentrations. The goal was to shed more light on the gas-phase chemistry during KCl-induced corrosion under conditions relevant to biomass combustion. CI-APi-TOF proved to be a valuable tool for high-temperature corrosion studies: HCl was identified to have formed during the reactions under humid conditions. On the contrary, despite the known sensitivity of CPFAAS, the formation of KOH could not be verified in any of the performed measurements.     

Local reactions of KCl particles with iron,nickel and chromium surfaces

Corrosion of superheaters caused by the deposition and subsequent reaction of alkali chloride containing ashes is one of the main material problems by combustion of biomass for energy conversion. The alkali chloride particles are formed during combustion and transported as aerosol or in the vapor phase within the combustion gas, subsequently sticking on the surface of the metallic tube. The initial reaction between the tube surface and the salt particle plays a major role in the initiation of the corrosion process and, therefore, are studied in detail in this work. The salt particles were locally deposited by means of thermophoresis within an aerosol generator, available at MPIE. Studies on the reaction of KCl particles with iron surfaces showed that a reaction takes place already at 300 °C. In N₂‐O₂ atmospheres, the attack was very local, whereas the addition of 0.05 vol.% HCl to the reaction gas led to complete coverage of the iron surface with chloride. In contrast, reactions of KCl with nickel and chromium surfaces start to be significant only at 500 °C and higher. The paper summarizes the reaction behavior of Fe, Ni and Cr after thermophoretic deposition of KCl particles and subsequent reaction at elevated temperatures.     

氢对304不锈钢阳极行为的影响

<正> 虽然奥氏体不锈钢在42％MgCl_2沸腾溶液中的应力腐蚀并不是由氢致开裂引起的,但在应力腐蚀过程中生成的氢可以进入试样并可在裂纹前沿富集。为澄清进入试样的氢是否对阳极溶解过程产生促进作用,曾有人用失重法、晶间腐蚀和极化曲线变化等研究氢对阳极行为的影响,并得出氢促进阳极溶解的结论。应当指出,充氢试样的阳极电流包括了氢的氧化电流,因此充氢后阳极电流的增大并不证明氢促进了阳极溶解过程。虽然失重法能反映氢的促进作用,但只适用于腐蚀较为严重的情况。     

Corrosion Behaviour of Manganese-Containing Stainless Steels. III. Their susceptibility towards pitting corrosion

The pitting susceptibility of stainless steels with (%) 17.39 Cr, 5.3 Ni, 0.3–13.9 Mn in chloride solutions have been studied by a potentiodynamic cyclic polarization technique in solutions 0.1 N H₂SO₄ + 0.9 N Na₂So₄ + various amounts of NaCl. At low NaCl concentrations no pronounced influence of the chloride can be found and even at medium concentrations the passivation behaviour is generally maintained; in this region, however, there is an increase of dissolution and passivation current densities. High chloride concentrations, however, result in pitting which may be completely suppressed by a cyclic (anodic/cathodic) polarization technique. As to pitting resistance an alloy containing (%) 17.3 Cr, 5.3 Ni, 5.6 Mn is comparable to the steel CrNi 18 9.     

The Influence of KCl and HCl on the High-Temperature Oxidation of a Fe-2.25Cr-1Mo Steel at 400 °C

The influence of alkali- and chlorine-containing compounds on the corrosion of superheater alloys has been studied extensively. The current paper instead investigates the corrosive effects of KCl and HCl under conditions relevant to waterwall conditions. A low-alloy (Fe-2.25Cr-1Mo) steel was exposed to KCl(s), 500 vppm HCl(g) and (KCl?+?HCl) in the presence of 5%O₂ and 20% H₂O at 400 °C. The results indicate that alloy chlorination by KCl occurs by an electrochemical process, involving cathodic formation of chemisorbed KOH on the scale surface and anodic formation of solid FeCl₂ at the bottom of the scale. The process is accompanied by extensive cracking and delamination of the iron oxide scale, resulting in a complex, convoluted scale morphology. Adding 500 vppm HCl to the experimental environment (KCl?+?HCl) initially greatly accelerated the formation of FeCl₂ at the scale/alloy interface. The accelerated alloy chlorination is attributed to HCl reacting with KOH at the scale surface, causing the cathodic process to be depolarized. A rapid slowing down of the rate of chlorination and corrosion in KCl?+?HCl environment was observed which was attributed to the electronically insulating nature of the FeCl₂ layer which forms at the bottom of the scale, disconnecting the anodic and cathodic regions.

     

铜表面BTA薄膜在强酸中耐蚀性的电化学阻抗研究

用电化学阻抗法研究铜在强酸中添加BTA(苯并三唑)及铜表面预覆BTA薄膜后在强酸中的耐蚀行为和机理。研究表明:在强酸溶液中,BTA与二价铜离子形成不同配位数的Cu—BTA配合物,在硫酸中抑制阳极反应,在盐酸中抑制阴极反应。在铜表面预覆BTA薄膜,对铜有更好的防蚀保护性能。     

快速凝固富钛Ti-V合金的微观组织和储氢性能

研究目的在于优化Ti0.8-0.9V0.2-0.1二元合金的相结构成分、微观组织和储氢性能。该合金主要用于从含有大量一氧化碳的高温气态混合物中吸收氢气。Ti0.8-0.9V0.2-0.1合金中的α-（HCP）和β-（BCC）相在纯氢气中基于氢化作用,形成单相FCC结构的氢化物,此过程与合金的化学成分无关。同步辐射X射线衍射的原位分析表明,在含有氢气和10%一氧化碳的混合气体中,只有β相转变成相应的氢化物。快速凝固（RS）处理细化了Ti0.8V0.2和Ti0.9V0.1合金的晶粒组织,而且,快速凝固处理增加了Ti0.9V0.1合金中的β相,其所占比例是普通熔铸条件下的两倍。扫描电子显微镜（SEM）分析表明,Ti0.9V0.1合金含有片状组织,层片的厚度约为300nm。热脱附谱（TDS）显示,微观组织的细化可以加快氢脱附的动力学过程。     

Physicochemical and catalytic properties of palladium deposited on polyaniline-coated silica gel

The chemical incorporation of palladium into polyaniline (PANI) deposited onto the silica gel microparticles (15-μm in diameter) was studied. The as-prepared silica particles coated with PANI–hydrochloride (AC) were treated with aqueous ammonia solution (0.1 M) to transform polyaniline to its base (BA) form. Both AC and BA samples were reacted with PdCl₂ solutions (2.3×10⁻³ M) strongly differing in the concentration of HCl (0.1 M HCl, series K; 6.6×10⁻⁴ M HCl, series Z). Two series of samples with 0.43–2.14 wt.% Pd were obtained. Fourier-transform infra red (FTIR), UV-Vis, X-ray photoelectron spectroscopies (XPS) and scanning electron microscopy have been used to examine the nature of processes involved upon insertion of Pd and to characterize palladium species in the final samples. Very similar palladium species were found in the polymer matrix independently of the acidity of PdCl₂ solutions and the extent of PANI protonation (AC and BA samples). Pd²⁺ was the only form if no more than 0.86% Pd was introduced. Incorporation of higher content of palladium resulted in the partial reduction (14.6–28.7%) of Pd²⁺ to Pd⁰. The presence of Pd²⁺ species in the form of complexes in which besides Cl⁻ ligands also nitrogen groups of PANI participated has been postulated. The catalytic properties of Pd/PANI-SiO₂ have been studied in the liquid-phase hydrogenation of 2-ethylanthraquinone (EAQ) at 60 °C under 1 atm of hydrogen. Very low activity of the as-prepared catalysts significantly increased due to reduction of the samples with NaH₂PO₂ and subsequently with dihydrogen. The specific activities of reduced series K and Z samples were comparable and the maximum activity exhibited catalysts with 1–1.5% Pd.     

Influence of cobalt,nickel and copper-based metal-organic frameworks on the corrosion protection of mild steel

Three metal-organic frameworks (MOFs) were synthesised and their corrosion prevention behaviour was evaluated. Trimesic acid was used as a ligand to synthesis cobalt, nickel and copper-based MOFs in a mixture of solvents. MOFs were characterised by X-ray diffraction, FT-IR spectroscopy and thermogravimetric analysis. FE-SEM images of Ni-MOF and Cu-MOF showed one-dimensional nanorods, and foam-like morphology respectively. That of Co-MOF displayed large chunky particles with etched edges, and of non-uniform size and shape. The corrosion behaviour of MOF pigmented paint coated on mild steel was studied in 3.5% NaCl and 0.1?N HCl solutions using electrochemical impedance spectroscopy (EIS). In both solutions, Ni-MOF exhibited higher corrosion resistance than the Co-MOF and Cu-MOF.     

Zr0.9Ti0.1V2合金循环吸放氢稳定性

研究了Zr0.9Ti0.1V2合金的循环吸放氢性能。合金在吸氢P-C-T曲线的特征区域内具有良好的循环吸氢稳定性,在P-C-T曲线的吸氢平台区（H/A为0.5左右）、吸氢形成氢化物初始阶段（H/A为1~1.2）、吸氢形成氢化物中间阶段（H/A为1.4左右）吸放氢循环测试中,每组循环内合金的吸氢量差别非常小,循环吸氢稳定性很好。经过70次吸氢循环后,合金的吸氢量可以恢复到1.957 (H/A),合金的粉碎程度很低,表明合金具有良好的循环吸氢能力     

Adsorbability of Thiourea on Iron Cathodes

The adsorption of thiourea on iron cathodes has been studied in 0.1 N sulphuric acid solution containing 10^?1 and 10^?2 Mol of thiourea at 30, 40 and 50 °C. The surface coverage has been calculated by comparing current density (at constant potential and temperature) of solutions with and without inhibitor. The results show that adsorption is due to specific adsorption forces of molecules and HS^? anions as well as to electrostatic forces of cations. The authors have determined the adsorption energy and the enthalpy, free standard energy and entropy of adsorption. On the basis of these results it is feasible to presume that thiourea would be rather efficient an inhibitor of the corrosion for iron acid solution.     

Effect of Thermal Oxidation on Corrosion Resistance of Commercially Pure Titanium in Acid Medium

This article addresses the characteristics of commercially pure titanium (CP-Ti) subjected to thermal oxidation in air at 650?°C for 48?h and its corrosion behavior in 0.1 and 4?M HCl and HNO₃ mediums. Thermal oxidation of CP-Ti leads to the formation of thick oxide scales (~20???m) throughout its surface without any spallation. The oxide layer consists of rutile- and oxygen-diffused titanium as predominant phases with a hardness of 679?±?43?HV_1.96. Electrochemical studies reveal that the thermally oxidized CP-Ti offers a better corrosion resistance than its untreated counterpart in both HCl and HNO₃ mediums. The uniform surface coverage and compactness of the oxide layer provide an effective barrier toward corrosion of CP-Ti. The study concludes that thermal oxidation is an effective approach to engineer the surface of CP-Ti so as to increase its corrosion resistance in HCl and HNO₃ mediums.