交流电干扰下Q235钢与铜在不同含水量北京土壤中的短期腐蚀行为

利用电化学测试和埋片试验研究了交流电干扰下Q235钢和铜在不同含水量北京土壤中短期腐蚀行为。结果表明:交流电对Q235钢与铜的腐蚀起到明显促进作用,对铜影响更大;交流电与土壤含水量对Q235钢的影响有明显的交互作用,对铜则无明显的影响;交流电主要影响材料的阳极反应过程,含水量主要影响材料的阴极反应过程;土壤含水量未达到饱和时,Q235钢与铜表面均发生腐蚀,且随着土壤含水量的增加,腐蚀均逐渐加重,其表面点蚀坑密度和深度均逐渐减小;在土壤含水量达到饱和时,Q235钢与铜表面均又出现较严重点蚀。     

Modeling and experimental calibration of the corrosion of RHA steel in immersion and salt-fog environments

ABSTRACT

An investigation into the general and pitting corrosion rates of rolled homogeneous armour (RHA) steel in immersion and salt-fog environments is presented. Although the mechanical properties of RHA steel have been studied, the corrosion effects on RHA steel have not been quantified. An immersion environment of 3.5% NaCl was used to induce corrosion for four immersion samples. A Q-fog corrosion tester was used to simulate a salt-fog/humidity/drying environment for four salt-fog samples. The different mechanisms of corrosion and their rates were quantified through mass loss, laser profilometry and scanning electron microscopy. The immersion samples show a linear rate of corrosion of 1.47?g/year (R²?=?0.994) throughout the entire testing period. The salt-fog samples had a significant mass gain for the first 500?h of corrosion, as the corrosion products are retained. Immersion samples showed no signs of pitting, while the salt-fog samples had sustained pit nucleation, growth, and coalescence.     

Effects of Tafel slope,exchange current density and electrode potential on the corrosion of steel in concrete

A parametric study is carried out to investigate the effect of variations in anodic and cathodic Tafel slopes, exchange current densities and electrode potentials on the rate of steel corrosion in concrete. The main goal of this investigation is to identify the parameters that have significant influence on steel corrosion rate. Since there is a degree of uncertainty associated with the selection of these parameters, particularly during modelling exercises, it is intended that the results of this study will provide valuable information to engineers and researchers who simulate steel corrosion in concrete. To achieve this goal, the effect of a parameter on the corrosion rate of steel is studied while all other parameters are kept constant at a predefined base case. For each parameter, two extreme cases of anode‐to‐cathode ratio are studied. The investigation revealed that the variations in the anodic electrode potential have the greatest impact on the corrosion rate, followed by the variations in the cathodic Tafel slope.     

Assessment of stress corrosion crack initiation and propagation in AISI type 316 stainless steel by electrochemical noise technique

Electrochemical noise (EN) analyses, using time domain, frequency domain and statistical parameters, were carried out on the potential and current data obtained on AISI type 316 stainless steel during (i) pitting corrosion in deaerated 0.5 M sodium chloride (NaCl) solution, and during (ii) stress corrosion cracking (SCC) in boiling acidified NaCl solution. Visual records and statistical analysis of the current and potential data alongwith the spectral estimation using maximum entropy method (MEM) gave useful informations on differentiating between these corrosion processes and on the effect of stress in accelerating pitting corrosion. The results correlated well with the optical microscopic observations.     

Electrodeposition of Tin Alloys from Alkaline Stannate Baths

The paper reports on a small development programme designed to concentrate on devising a relatively simple technique for the deposition of copper only in drilled holes of a conventionally produced printed wiring board. It is essential to start with a laminate containing catalysed resin base, producing the printed wiring pattern in the normal manner and plating up holes using autocatalytic electroless copper. Thickness measurements and microsections of electroless copper deposits have been obtained and appear to be encouraging.     

温度和外加电位对X70管线钢在土壤模拟溶液中应力腐蚀行为的影响

采用动电位扫描、慢应变拉伸（SSRT）和扫描电镜观察研究了温度和外加电位对X70管线钢在成都土壤模拟溶液中的应力腐蚀行为的影响。结果表明,在不同温度和不同电位下,X70管线钢在土壤模拟溶液中表现出不同的应力腐蚀敏感性。在温度和外加电位的交互试验中,电位的变化对X70管线钢在成都土壤模拟溶液中的应力腐蚀敏感性的影响占主导地位,应力腐蚀敏感性在不同温度下的变化趋势保持一致。在－450 mV(vs SCE,下同)的阳极电位下,SCC的机理为阳极溶解;在－850 mV电位下,阴极保护作用抑制了阳极溶解;当电位负移至－1200 mV时,表现出较强的应力腐蚀敏感性,SCC机理以氢脆为主。温度对应力腐蚀敏感性的影响主要体现在对阴极极化电位的影响,但是各种因素综合在一起导致应力腐蚀敏感性随温度变化的复杂性。     

Evaluation of the BEASY program using linear and piecewise linear approaches for the boundary conditions

The boundary element method (BEM) was used to study galvanic corrosion using linear and logarithmic boundary conditions. The linear boundary condition was implemented by using the linear approach and the piecewise linear approach. The logarithmic boundary condition was implemented by the piecewise linear approach. The calculated potential and current density distribution were compared with the prior analytical results. For the linear boundary condition, the BEASY program using the linear approach and the piecewise linear approach gave accurate predictions of the potential and the galvanic current density distributions for varied electrolyte conditions, various film thicknesses, various electrolyte conductivities and various area ratio of anode/cathode. The 50‐point piecewise linear method could be used with both linear and logarithmic polarization curves.