镁水泥混凝土中钢筋的电化学腐蚀研究

为解决分布在西部盐湖地区出现的煤矿矿区钢材腐蚀问题,结合煤矿矿区实际环境,采用实验、理论分析等方法研究了镁水泥混凝土中钢筋的腐蚀.采用CS350电化学工作站,研究镁水泥混凝土中钢筋的电化学腐蚀,结合SEM微观实验和EDS元素扫描结果,对镁水泥混凝土中裸露钢筋腐蚀状况进行描述.研究表明:美加力涂层钢筋状态良好,未出现腐蚀状态;锌美特涂层钢筋出现了低腐蚀现象;而裸露钢筋表面出现了严重腐蚀.钢筋涂层防腐蚀性美加力涂层较好,锌美特涂层次之;涂层钢筋虽然防腐效果不同,但对裸露钢筋的防腐蚀性能有明显有利影响.     

碳酸钙晶须与硅灰的复合效应对水泥砂浆力学性能的影响

研究了水泥砂浆的抗压强度、抗折强度以及劈裂抗拉强度在固定硅灰掺量的条件下随着碳酸钙晶须掺量的变化关系,并以试验结果和微观形貌观察为基础探讨了碳酸钙晶须对水泥砂浆的增强增韧机理。     

Electrochemical activity of heavy metal oxides in the process of chloride induced corrosion of steel reinforcement

The influence of heavy metal oxides on the chloride induced corrosion of steel reinforcement in concrete was studied. Significant inhibition and stimulation of chloride induced corrosion have been observed. Basicity and acidity of the relevant metal ions, and their ability to form complexes are considered as the main factors of the observed effects.     

Behaviour of high volume fibre cement mortar in flexure

Tests are reported on the behaviour of high volume percentage steel fibre mortar specimens subjected to flexure. Flexural and cyclic load tests were conducted; in addition, comparison tests were made on conventional fibre mortar and ferrocement specimens. Both strength and deflection characteristics were studied. The results of the investigation indicate that with 8% high volume, steel fibre mortar specimens possess a flexural strength of about 40 MPa.     

复合缓蚀剂对模拟混凝土孔隙液中钢筋的阻锈作用

应用电化学技术和扫描电子显微镜(SEM)等方法,研究了亚硝酸钠和D-葡萄糖酸钠复合缓蚀剂对模拟混凝土孔隙液中钢筋腐蚀行为的影响及其阻锈作用.结果表明,复合缓蚀剂主要起阳极型缓蚀剂作用.含3.5%NaCl,pH值为11.00的模拟液中加入含5g/L亚硝酸钠的复合缓蚀剂后,钢筋的腐蚀电流降低至未加缓蚀荆的1%,缓蚀效率达99%.     

冷却工艺对货油舱用耐蚀钢组织性能的影响

基于货油舱用耐蚀钢的服役环境设计并冶炼了一种新型耐蚀钢,根据试验钢变形奥氏体连续转变曲线,采用控制轧制和控制冷却的技术将锻后110 mm坯料减薄至16 mm。热轧板材的年平均腐蚀速率分布在0.235~0.273 mm/a,小于船级社要求的1 mm/a。利用扫描电镜、透射电镜、拉伸试验机和冲击试验机进行了耐蚀钢的显微结构分析及力学性能研究,探究了控制冷却工艺对耐蚀钢组织性能的影响规律。结果表明:在终冷温度669 ℃、冷却速度8.9 ℃/s的条件下,耐蚀钢显微组织主要为铁素体、贝氏体和退化珠光体。降低终冷温度或提高冷却速率有利于抑制珠光体转变,促进针状铁素体和贝氏体相变进程,增加小角度晶界数量,提高耐蚀钢的组织均匀性和力学性能。当终冷温度降低至597 ℃,冷却速度增大到13.1 ℃/s,耐蚀钢组织为针状铁素体、粒状贝氏体和板条贝氏体混合结构,不均匀分布且粗大尺寸的板条结构弱化了材料的抗冲击性能。     

Protection of reinforcement steel corrosion by phenylphosphonic acid pre-treatment PART II: Tests in mortar medium

A pre-treatment of steel reinforcement in mortar by a 72 h immersion in 0.1 M phenyl-phosphonic acid (C₆H₅P(O)(OH)₂; PPA) was investigated. Then effectiveness of this procedure for protection against the corrosion of steel bars embedded in pre- or post-addition of sodium chloride mortar was evaluated by electrochemical impedance spectroscopy, visual inspection, SEM, and EDS analyses.The results showed that for non-treated steel reinforcement, the charge transfer resistance (R_t) decreases considerably with time indicating a very advanced state of corrosion after 54 months corrosion test. In contrast, for pre-treated steel rebar, this resistance remains high reflecting the effectiveness of the pre-treatment method against corrosion. The corrosion rate evaluated from the charge transfer resistance at 54 months corrosion in chloride containing medium was 0.5 μm year⁻¹.     

Stress corrosion cracking of AISI 321 stainless steel in acidic chloride solution

The stress corrosion cracking (SCC) of AISI 321 stainless steel in acidic chloride solution was studied by slow strain rate (SSR) technique and fracture mechanics method. The fractured surface was characterized by cleavage fracture. In order to clarify the SCC mechanism, the effects of inhibitor KI on SCC behaviour were also included in this paper. A study showed that the inhibition effects of KI on SCC were mainly attributed to the anodic reaction of the corrosion process. The results of strain distribution in front of the crack tip of the fatigue pre-cracked plate specimens in air, in the blank solution (acidic chloride solution without inhibitor KI) and in the solution added with KI measured by speckle interferometry (SPI) support the unified mechanism of SCC and corrosion fatigue cracking (CFC).     

Effect of latex and superplasticiser on Portland cement mortar in the fresh state

This report deals with the individual and combined effect of latex and superplasticiser on Portland cement mortar in the fresh state. The compatibility of five commercial superplasticisers with four latexes of the vinyl polymer group and SBR latex in varying dosages was studied with respect to setting time, consistency of fresh cement pastes, subjective workability (surface texture, segregation), bleeding, air content, water reduction capacity and the flow-time relationship of fresh mortar. It has been observed that superplasticisers of melamine formaldehyde and a blend of melamine and naphthalene formaldehyde eliminated shortcomings like delayed setting, high air entrainment in the fresh latex-modified system whereas lignosulphonate and a blend of lignosulphonate and naphthalene formaldehyde aggravated it. In a consequent report, performances in the hardened state will be discussed.     

Cu合金化对Cr9Mo1钢耐腐蚀及力学性能的影响

为了研究Cu元素对含Mo高Cr钢耐腐蚀性及力学性能的影响,本文通过添加Cu元素和热轧工艺,制备了含有0.2%(质量分数)Cu元素的两组不同含C量的Cr9Mo1钢.利用拉伸试验机、光学显微镜(OM)及盐雾试验箱等,对比研究了添加Cu元素前后,Cr9Mo1钢力学性能、组织形貌及耐盐雾腐蚀性能的变化.结果表明,添加Cu元素均可显著提高Cr9Mo1钢的耐腐蚀性,但对力学性能及组织形貌无显著影响.低C钢组添加Cu元素后耐腐蚀性显著提高,强度和延伸率仅略有提高;高C钢组添加Cu元素后耐腐蚀性显著提高,强度略有提高,延伸率有所降低.热轧后的低C钢组的基体组织为混晶铁素体,高C钢组的基体为马氏体组织和少量δ铁素体.C含量的多少主要影响钢的力学性能,对耐腐蚀性的影响无显著差异.相较于含C量低的Cr9Mo1钢,含C量高的Cr9Mo1钢强度较高、塑性较差,但耐腐蚀性基本相同.     

模拟混凝土孔隙液中钢筋电化学腐蚀行为及pH值的影响作用

应用极化曲线法和电化学阻抗技术,结合扫描电子显微镜方法,测试钢筋在模拟混凝土孔隙液中的钝化与去钝化行为,以及溶液pH值对钢筋电化学腐蚀行为的影响作用.结果表明,钢筋在pH值为12.50的模拟液中处于钝态,随着溶液pH值的降低,钢筋的耐蚀性下降.钢筋表面去钝化发生腐蚀的临界PH值在11.12-11.05范围内.     

萘系减水剂对硬化水泥浆体及孔隙液中钢筋腐蚀的影响

为了研究外加剂对混凝土中钢筋腐蚀的影响,模拟了混凝土孔隙液及制备了硬化水泥浆体,研究了添加不同含量的萘系减水剂对钢筋腐蚀的影响.结果表明:在模拟混凝土孔隙液中加入萘系减水剂对钢筋腐蚀有轻微的促进作用,当减水剂含量达到一定值时腐蚀增大的趋势就会消失;在硬化水泥浆体中加入萘系减水剂可以减缓钢筋的腐蚀,添加0.5%萘系减水剂阻锈效果最明显,且随着时间的延长,萘系减水剂对硬化水泥浆体中钢筋的阻锈效果增加;加入减水剂增强了硬化水泥浆体的密实性,从而减缓了钢筋的腐蚀.     

钨和碳双注入H13钢抗磨损和抗腐蚀特性

首次研究了钨和碳双注入对抗磨损和抗腐蚀特性的影响，研究了抗磨损和抗腐蚀相生成的条件，以及这些相对抗磨损和抗腐蚀特性的作用，并对其改进机理进行了讨论。实验结果表明，钨和碳双注入H13钢可注入层中形成超饱和的钨和碳原子浓度。因此在注入层中形成钨的碳化物WC和W2C相，合金相Fe2W和Fe2W6C等，这些弥散相不但可以使注入具有钨和碳单注入的特性，所以能进一步地提高H13钢的抗腐蚀性，随着W和C注入剂量的增加，抗磨损和抗腐蚀特性进一步提高，抗磨损特性可改善2倍，双注入样品抗腐蚀特性也有明显也提高，如样品W5C8的腐蚀电流峰值密度Jp经55个周期腐蚀后，其值是H13钢Jp的1／26.7-1/33.3，而钨样品C5W5经过88个周期腐蚀后，其值是H13钢的1／16－1／20。     

Effect of cathodic potential on stress corrosion cracking behavior of different heat-affected zone microstructures of E690 steel in artificial seawater

In this work,the stress corrosion cracking(SCC)behavior of E690 steel base metal(BM)and different heat-affected zone(HAZ)microstructures,i.e.,coarse grain HAZ(CGHAZ),fine grain HAZ(FGHAZ),and intercritical HAZ(ICHAZ),was investigated at different cathodic potentials in artificial seawater by slow strain rate tensile tests,scanning electron microscopy and electron back-scattered diffraction measurements.The results show that the HAZ microstructures and BM exhibit different SCC susceptibilities:FGHAZ相似文献   

Corrosion inhibition of benzyl triethanol ammonium chloride and its ethoxylate on steel in sulphuric acid solution

The inhibitive effect of benzyl triethanol ammonium chloride (BTAC) and ethoxylated benzyl triethanol ammonium chloride (EBTAC) on the corrosion of carbon steel in sulphuric acid solution is measured by the weight loss method. The adsorption of these compounds (surfactants) leads to the formation of a monolayer on the metal surface. The relationships between the concentrations of these inhibitors and their surface properties, thermodynamic properties, surface coverage (θ) and inhibiting efficiency have been investigated. The results indicate that EBTAC is superior to BTAC.