Electrochemical impedance spectroscopy of a free-standing oxide film

The corrosion of low carbon steel in natural sea-water is characterized by the formation and growth of compact and thick layers composed of oxides, insoluble salts and organic materials. These layers are the result of corrosion processes induced by local environmental conditions, water oxygen supply; ionic species; bacteria and organic matter. The exchange of various species (ions, molecules, gas) between sea-water and the rust layers or the metal depends both on the kinetics of the Faradaic reactions of the entities with either the oxides or the metal, as well as on their transport properties through the different strata of the rust layers. In this work, an impedance study was carried out using the 4-electrodes cell arrangement with corrosion products picked up on steel sheet piling immersed for 25 years and analyzed as free standing membranes. This new approach is a good way to reach the specific transport and transfer properties of the oxide without being blurred by the metal influence. The physical model developed in this work was based on a transmission line, and accurately described the experimental diagrams. The electronic resistivity of the oxide layer, its porosity, the mean pore size and the reaction kinetics parameters could be determined from the fittings.     

凸轮进给式双管平头倒棱机

研制的凸轮进给式双管平头倒棱机可自动完成上料→夹紧→平头倒棱→松开→退料动作循环，同步准确，可靠性高，平头倒棱质量好。介绍了该装置的工作原理、工作程序、技术性能、设备组成以及刀具和夹具的特点。     

钢纤维聚合物混凝土抗压本构关系

钢纤维聚合物混凝土是由聚合物混凝土基体和钢纤维共同组成的纤维增强复合材料，它的力学行为不仅依赖于聚合物混凝土基体的行为，而且与钢纤维的掺量、分散特征以及钢纤维的几何尺寸有关，本文将基于损伤力学原理研究在不同纤维掺量下的钢纤维聚合物混凝土的全程压力-应变曲线及其本构模型。     

西气东输工程用X70热轧板卷屈服强度检测值波动大的探讨

对西气东输工程用X70热轧板卷检验过程中出的屈服强度σ0.5波动大的情况进行了分析，认为拉伸试样弯曲是主要原因。这一问题可通过反复压平试样，确保试样的平直度以及适当提高钢的强度的方法加以解决。     

Influence of the surface conditions on permeation in the deuterium–MANET system

The condition of the surfaces is of crucial importance for the deuterium permeation through materials. In this work a study of the surface constants for the adsorption (σk₁) and release (σk₂) of deuterium under different surface conditions on the martensitic steel DIN 1.4914 (MANET) has been carried out. The growth of an oxide surface layer (Cr₂O₃) of about 25–30 nm in a MANET sample, heat treated in an oxidizing environment, compared to the bare MANET that have a ‘natural' oxide of about 5 nm has provoked a reduction of both the permeation rate and the recombination coefficient (about 3 orders of magnitude). In addition, the permeation governing process has changed from diffusion-limited to surface-limited. The measurements of the permeation rate of deuterium were performed by a gas-phase permeation technique over the temperature range 574–746 K and for deuterium driving pressures in the range from 3 to 10⁵ Pa.     

A comparative study of color measurement lntstrumentation

A multiplant Quality Improvement Team [QIT] was firmed to develop and implement an evaluation program for various color measurement .systems as potential replacements for the then-current aging systems. The emphasis qf this article is the analytical methodology utilized to evaluate the various color systems. The evaluation program consisted cf two phases. Phase I was a general overview/review of several systems, while Phase II was an extensive internal comparative evaluation measurement systems. These were Milton-Roy's ColorMate HDS, HunterLab's Ultrascan, Datacolor's CS-5, and BYK-Gardner's The Color Sphere [TCS]. The main comparison criteria were interinstrument agreement [agreement between two instruments ofthe same system], user-friendly software and computer interface capability, vendor amenability to a long-term logistical and maintenance relationship, and price. All systems were evaluated by duplicate measurements on various color tiles, yarns, and polymer flakes-over 1600 measurements on each system. The systems were compared with an instrument matrix, a decision matrix, and a product matrix. The instrument matrix was a comparison qfinstrument parameters, software/math treatments, and economics. The decision matrix was a forced ranking of each system by each criteria category [1–4 scale, with 1 representing the best and 4 representing the worst]. The product matrix accentuated the relative importance ofone criterion category over another by multiplying the forced ranking by the criticality of the category. The criticality of a given category wus determined by consensus within the QIT. Thr combination qf the three matrices allowed the evaluator[.s] t o select the color rneasuremmt system that best satixfied the color measurement needs and requirements of their facility and their products. For this evaluation, all ofthe evaluated systems were superior to the then-current agingsystems. As a result of this methodology, one instrument emerged as clearly superior. © 1994 John Wrley & Sons, Inc.     

A new alloy design concept for austenitic stainless steel with tungsten modification for bipolar plate application in PEMFC

The feasibility of a new alloy design concept utilizing the principle of ‘tungsten bronze effect’ is critically evaluated for the development of metallic bipolar plates for proton exchange membrane fuel cell (PEMFC). An austenitic stainless steel (ASS) is modified with W and La to improve the stability of the passive film in an acidic environment as well as to reduce the contact resistance by the tungsten bronze effect. The experimental ASS containing W and La was evaluated in a simulated PEMFC environment of H₃PO₄ and H₂SO₄ solutions at 80 °C, and the electrical property was evaluated by performing a contact resistance test. The test results show that the ASS modified with W and La has good passive film stability for corrosion resistance and low contact resistance. The X-ray photoelectron spectroscopy (XPS) analysis clearly suggests the possibility of the tungsten bronze effect from the change in valency state of W⁶⁺ to W⁵⁺ in the passive film formed on the modified ASS. The feasibility of a new alloy design concept utilizing the ‘tungsten bronze effect’ is well demonstrated; however, more study is highly required for the development of metallic bipolar plates of PEMFC.     

Evaluation of different coating systems by electrochemical methods

Corrosion protection of organic coated steel is determined by free corrosion potential measurements and impedance spectroscopy. The results are classified by means of very basic considerations and evaluation figures are developed. These electrochemical data are correlated with the extent of the corrosion for each coating system. The evaluation figures are used for ranking coating systems and this ranking is correlated with the ranking with reference to the results of standardized and exposure tests.