Theoretical description of the practical possibility of stress corrosion cracking from crevice corrosion sites

Stress corrosion cracking (SCC) from crevice corrosion sites had been found in an experimental work at polarization potential of + 200 mV_SCE. In that work, an occluded U‐bend specimen of Type 316L (UNS S31603) stainless steel was used. The testing was done in sodium chloride (NaCl) solution. Based on that work, the practical possibility of SCC from the occluded U‐bend specimen was described theoretically. It was shown that it would also be possible for SCC to occur in practice (i.e. at practical corrosion potential), but the crevice needs to be tighter. Meanwhile, it would take a longer time for obvious SCC to emerge. For a practical crevice usually formed by placing a crevice former on a large uniform metal surface, the crevice geometry may have little effect on SCC although the crevice can sustain an acidified solution more easily than pitting. The possibility of SCC should mainly depend on the corrosion system itself, i.e. material and environment.     

ISO 4406新旧标准简介及修订原因说明

介绍了评定液压和润滑系统油液污染度等级的新旧两种国际标准ISO4406：1999和ISO4406：1987，其中ISO4406：1999污染度等级标准是对ISO4406：1987污染度等级标准的修订。新标准将等级代码增加到了30个，并且对报告形式和报告采用的污染颗粒尺寸都进行了修订。标准修订的根本原因是由于试验粉尘的改变（由ISOMTD粉末取代了ACFTD）以及相应的颗粒计数器校准方法的改变。     

Polyamine compound as a volatile corrosion inhibitor for atmospheric corrosion of mild steel*

Bis‐piperidiniummethyl‐urea (BPMU) was developed as a volatile corrosion inhibitor (VCI) for mild steel. Its vapor corrosion inhibition property was evaluated by volatile inhibiting sieve test (VIS). Electrochemical measurements were conducted in simulated atmospheric corrosion water. Electrochemical impedance spectroscopy of a volatile corrosion inhibitor monitor cell (VCIM) was applied to study the effect of BPMU on the corrosion inhibition of mild steel under a thin electrolyte layer. The results show that BPMU has good protection effect for steel. It suppressed the anodic reaction of the steel electrode in a manner of promoted passivation. Fourier transform infrared (FT‐IR) spectroscopy was used to characterize the adsorption of BPMU on the steel surface.     

Coatings against corrosion and microbial adhesion

A systematic study on anti‐corrosion and anti‐fouling effect of hydrophobic Langmuir–Blodgett and self‐assembled molecular layers deposited on metal surfaces, as well as anti‐microbial adhesion properties of coatings with biocide is presented. Both types of efficiencies produced by LB films are enhanced by Fe³⁺ ions built in the molecular film. The quaternary ammonium type biocide embedded into the cross‐linked gelatin decreased significantly the microbial adhesion, the biofilm formation.     

Effect of Sn addition on the corrosion behavior of Ti‐Ta alloy

In the present paper, the effect of Sn addition on phase constitution and corrosion behavior of Ti₆₅Ta_(35?x)Sn_x (x = 0, 1, 3, 5 at%) alloys has been investigated using X‐ray diffraction and electrochemical measurements. The results show that the β phase is stabilized when quenching after the addition of Sn into Ti₆₅Ta₃₅ alloy, with Ti₆₅Ta₃₀Sn₅ alloy consisting of single β phase at room temperature. The corrosion resistance is enhanced with increase in the Sn content. When the Sn content increases up to 5%, the addition of Sn results in a decrease of corrosion current density from 0.690 µA/cm² of the Ti₆₅Ta₃₅ alloy to 0.098 µA/cm², and corresponding passive current density decreased from 37.7 µA/cm² of the Ti₆₅Ta₃₅ alloy to 9.30 µA/cm².     

A new theory for the negative difference effect in magnesium corrosion

An unusual feature known as the negative difference effect (NDE) can be observed in magnesium when recording corrosion current density–potential curves. More hydrogen is evolved at a more positive potential which does not occur in conventional metals. Several models have been proposed in the literature in order to explain the phenomenon of NDE. They succeed in explaining some effects, and fail to deal with others. A new model, which explains the NDE by two electron consuming processes, is presented in this paper. By potentiostatic investigations of magnesium in a chloride electrolyte, measurements of hydrogen evolution and chemical analysis of the electrolyte the new model was experimentally verified.     

浅谈贯彻ISO9000系列标准及进行内部审核的必要

本文对贯彻ＩＳＯ９０００标准及进行内部审核的必要性作了阐述。     

Integral diagnostic in the failure causes of external corrosion of a natural gas transport pipeline

The objective of this study consisted in investigating the possible causes which give rise to the presence of low wall pipe thicknesses on a 16″ natural gas transport pipeline, even though during the last 12‐year period cathodic protection (CP) potentials were kept in the protection range at which external corrosion should not occur. Results from in‐line inspection from a 16″ natural gas transport pipeline showed 46 indications with more than 80% wall thickness lost due to external corrosion in the second segment of the pipeline. Direct inspection at the indication locations, review of the CP system performance, pipeline maintenance programs and studies, allowed to make an integral diagnostic where it was found out that the main cause of external corrosion was an inappropriate coating application since the pipeline construction, this situation has originated the increase of CP shielding effects through time.     

ISO9000质量管理体系在耐磨铸件生产中的作用

本文对耐磨铸件生产过程中影响产品质量的因素进行了分析。提出建立科学的IS09000质量管理体系，对稳定、提高耐磨铸件的质量是极为有利的。     

Morphology of corrosion products of steel in concrete under macro‐cell and self‐corrosion conditions

In this paper investigations into the formation of specific corrosion products during the process of chloride induced corrosion of steel in concrete are presented. The extension of corrosion products within concrete was established by means of X‐ray tomography analyses. Then a detailed analysis of the nature of corrosion products has been conducted by means of Raman micro‐spectroscopy and energy dispersive spectroscopy. Results emphasize two different corrosion patterns. The first one is composed of shallow cavities, where mostly magnetite and goethite were identified, traducing aerated to moderate aerated conditions in these media. The second pattern was identified as deep, needle‐like pits, where chlorinated‐iron‐oxides phases were present associated with more or less important chloride enrichments. The presence of these particular species is indicating low redox and low pH conditions within these pits.     

基于协同商务的Web三维零件库研究

协同产品商务可以使得目前的制造业企业在更短的时间内，以更个性化的服务，更低的成本，更少的缺陷制造出更好的产品。协同产品商务要求产品生命周期中的设计人员。供应商等能够方便地访问和共享产品数据，包括零件库。文章提出并建立了一种基于Web的、遵从ISO13584标准的、可用于协同商务的三维零部件库。     

A practical method for calculating the corrosion rate of uniformly depassivated reinforcing bars in concrete

The quantification of active corrosion rate of steel in concrete structures through nondestructive methods is a crucial task for scheduling maintenance/repair operations and for achieving accurate service life predictions. Measuring the polarization resistance of corroding systems and using the Stern‐Geary equation to calculate the corrosion current density of active steel is a widely‐used method for this purpose. However, these measurements are greatly influenced by environmental factors; therefore, accurate monitoring of corrosion requires integrating the instantaneous corrosion rates over time. Although advanced numerical models are helpful in research settings, they remain to be computationally expensive and complex to be adopted by general engineering community. In this paper, a practical numerical model for predicting corrosion rate of uniformly depassivated steel in concrete is developed. The model is built on Stern's earlier work that an optimum anode‐to‐cathode ratio exists for which the corrosion current on the metal surface reaches a maximum value. The developed model, which represents the corrosion rate as a function of concrete resistivity and oxygen concentration, is validated using experimental data obtained from the literature.