The development of ion-bombardment surface structures on stainless steel

A brief review is given of the formation and characteristics of conical surface structures resulting from ion etching. The effect of low-energy ion bombardment of 18-8 stainless steel surfaces has been studied. The topography generated has been related to microstructural detail. The conical protrusions are found to arise from slag silicate particles while the pillar type structures result from fibrous manganese sulphide inclusions. Scanning electron microscopy has shown the development of both of these structure types to be in accord with previously published ion-etching models.     

Laser cleaning of steel structure surface for paint removal and repaint adhesion

Paint removal from steel structure is executed for shipyards of marine and offshore engineering. Due to environmental unfriendliness and unhealthy drawbacks of sand blasting technique, laser ablation technique is proposed as a substituting method. By absorbing high energy of the 1064 nm pulsed laser, the paint is vaporized quickly. The ablated debris is then collected by using a suction pump. Initial metal surface of the steel is exposed when laser beam irradiates perpendicularly and scans over it. The cleaned surface fulfills the requirements of surface preparation standards ISO 8501 of SA2. The adhesion is further characterized with pull-off test after carrying out painting with Jotamastic 87 aluminum paint. The repainting can be embedded onto the laser cleaned surface to bond much more tightly. The excellent adhesion strength of 20 MPa between repainted coating and the substrate is achieved, which is higher than what is required by shipyards applications.     

Bond of ribbed galvanized reinforcing steel in concrete

The ASTM beam end test (ASTM A944) has been used to compare the bond and slip behaviour of deformed (i.e. ribbed) galvanized, epoxy-coated and black steel bars in concrete. The objective was to determine whether galvanizing adversely affects bond strength. From a series of thirty specimens, the average bond strength of black steel and galvanized steel reinforcement used in these tests has been determined and bond stress has been shown to act uniformly over the embedded bar area. A slip value of approximately 0.4 mm has been confirmed to be associated with bond failure by concrete splitting. The results indicated that while epoxy coating resulted in a significant loss in bond strength of the order of 20% compared to black steel, there is no adverse effect on bond with the use of galvanized steel. Chromate treatment of galvanized bars is deemed unnecessary since there was no evidence of long term reduction in bond due to the possible effects of hydrogen gas evolution resulting from the reaction between zinc and wet concrete.     

Prediction of fatigue resistance of a hot-dip galvanized steel

The paper clarifies the effect of a galvanizing coating on the fatigue strength of a ferritic steel. Depending on experimental conditions and on the microstructure of the coating, a reduction in fatigue strength is observed especially when the coating is thick. Cracks in the galvanizing coating rapidly form under cyclic loading and then propagate into the steel substrate. This completely modifies the distribution of crack lengths. Very short cracks are not observed in the steel when galvanized. It is shown that the propagation of a crack in the substrate from the coating is only possible when the crack completely crosses the coating. By assimilating the coating thickness to a crack in the steel substrate, the fatigue resistance of hot-dip galvanized steel can be predicted using the Kitagawa–Takahashi diagram.     

In vitro study of platelet adhesion on medical nickel-free stainless steel surface

A new nickel-free austenitic stainless steel, named BIOSSN4, has been recently developed to avoid the sensitivity to Ni ions. In the present study, the blood compatibility of the nickel-free stainless steel was evaluated in vitro by the platelet-rich plasma adhesion test with comparison to 316L stainless steel. The result shows that the nickel-free stainless steel only causes less activation of platelets, which was indicated by their morphology and low spreading. The result suggests that the nickel-free stainless steel should have better blood compatibility compared with 316L stainless steel and, as a bio-material, it should have obvious advantage and potential applications.     

Dissimilar metals TIG welding-brazing of aluminum alloy to galvanized steel

Dissimilar metals TIG welding-brazing of aluminum alloy to galvanized steel was investigated, and the wettability and spreadability of aluminum filler metal on the steel surface were analyzed. The resultant joint was characterized in order to determine the brittle intermetallic compound (IMC) in the interfacial layer, and the mechanical property of the joint was tested. The results show that the zinc coated layer can improve the wettability and spreadability of liquid aluminum filler metal on the surface of the steel, and the wetting angle can reach less than 20°. The lap joint has a dual characteristic and can be divided into a welding part on the aluminum side and a brazing part on the steel side. The interfacial IMC layer in the steel side is about 9.0 μm in thickness, which transfers from (α-Al + FeAl₃) in the welded seam side to (Fe₂Al₅+ FeAl₂) and (FeAl₂+ FeAl) in the steel side. The crystal grain of the welded seam is obviously larger in size in the aluminum side. The local incomplete brazing is found at the root of the lap joint, which weakens the property of the joint. The fracture of the joint occurs at the root and the average tensile strength reaches 90 MPa.     

Corrosion behaviour in concrete of three differently galvanized steel bars

The increasing use of galvanized steel reinforcements in concrete structures submitted to aggressive environments induces research into innovative zinc coatings with higher corrosion resistance. In this work, several cylindrical concrete specimens were manufactured with two cements of different alkalinity and reinforced with different hot-dip galvanized bars obtained from the “traditional” Zn–Pb bath and from two “modified baths”: Zn–Ni–Bi and Zn–Ni–Sn–Bi. The corrosion rate and corrosion potential of the bars were monitored during the air curing period and during wet–dry exposure both in tap water and in a 5% sodium chloride solution. The results showed that the coatings obtained from Zn–Ni–Sn–Bi bath have the highest corrosion rates, when the aggressiveness of the concrete matrix is determined mainly by its alkalinity. On the contrary, when the corrosion process is determined mainly by the penetration of chlorides (concrete manufactured with cement having a low alkali content) Zn–Ni–Sn–Bi was attacked only when the chloride concentration at the concrete cover depth reached the threshold of 4.02% (by weight of cement), which is higher than those necessary for the attack of the other coatings studied (1.36% for Zn–Ni–Bi, 1.73% for Zn–Pb).     

Studies on the presence of copper in the galvanized coating on weathering steel and the adherence characteristic of the protective copper complex formed on galvanized weathering steel

Following the hot-dip process for zinc coating on weathering steel, the galvanizing bath was found to have picked up copper. The galvanizing bath was observed to pick up Cu from the weathering steel at an average rate of 1.83×10^–3% s^–1m^–2 at 452±2C. EDAX/SEM studies exhibited a concentration gradient of copper to exist across the thickness of the galvanized coating on weathering steel. XRD studies revealed the formation of a protective copper complex, {Cu[(OH)₂Cu]₃}SO₄, on galvanized coating containing 0.739% Cu, when exposed in marine and industrial atmospheres. The adherence characteristic of the copper complex to the galvanized coating was found to be very satisfactory.     

The effects of sulphur dioxide on atmospheric corrosion of galvanized steel

Abstracts are not published in this journal     

热镀锌钢材在海洋大气环境中的氢渗透行为

用改进的Devanathan双面电解池在恒温、恒湿)条件下检测热镀锌钢材的渗氢电流密度并观测其腐蚀形貌,研究了温度对其氢渗透行为的影响.结果表明,在湿度相同的条件下,随着模拟海洋大气环境温度的升高试样的氢渗透加速,且湿度越高温度的这种加速作用越显著;在高温和高湿条件下,试样的氢吸收和氢渗透进行得更快.     

The effects of sulphur dioxide on atmospheric corrosion of galvanized steel

Abstracts are not published in this journal This revised version was published online in November 2006 with corrections to the Cover Date.     

A Mössbauer study of Fe-Zn phases on galvanized steel

Electron back-scattering Mössbauer spectroscopy has been used to examine the Fe-Zn intermetallic phases produced on galvanized steel. Spectra have been obtained from surfaces of the zeta, delta-prime (palisade), delta-prime (compact) and capital gamma phases, and these are discussed in terms of the crystal structure of each intermetallic phase.     

Corrosion kinetics and patina evolution of galvanized steel in a simulated coastal-industrial atmosphere

The corrosion kinetics and patina (corrosion products) layer evolution of galvanized steel submitted to wet/dry cyclic corrosion test in a simulated coastal-industrial atmosphere was investigated. The results show that zinc coating has a greater corrosion rate during the initial period and a lower corrosion rate during the subsequent period, and the patina composition and structure can greatly affect the corrosion kinetics evolution of zinc coating. Moreover, Zn₅(OH)₆(CO₃)₂ and Zn₄(OH)₆SO₄ are identified as the main stable composition and exhibit an increasing relative amount; while Zn₁₂(OH)₁₅Cl₃(SO₄)₃ cannot stably exist and diminish in the patina layer as the corrosion develops.     

镀锌钢的液态金属脆现象及其在电阻点焊过程中的表现

液态金属脆是指通常具有韧性的固体金属或者合金与液态金属直接接触且受到拉伸应力时,其塑性降低并发生脆性断裂的现象。钢在液态锌中会发生液态金属脆现象,这在镀锌钢的热拉伸实验中得到了证实。此外,研究人员发现在镀锌高强钢的电阻点焊过程中也会出现液态金属脆现象,表现为在焊点表面出现大量裂纹,这些裂纹对焊点性能存在潜在危害。本文回顾了镀锌钢液态金属脆现象的热拉伸实验研究,阐明了影响脆化现象的实验因素;综述了镀锌钢在电阻点焊过程中发生液态金属脆现象的研究进展,分析了产生裂纹的位置及其影响因素,并总结了可能的解决方案。     

Efficiency of certain chromate-free pigments for the corrosion protection of galvanized steel

By using electrochemical methods of a.c. and d.c. and electron microscopy, we investigated the corrosion behavior of galvanized steel in a slightly acid medium that simulates atmospheric precipitation and contains extracts of chromate and chromate-free pigments. We established that the joint use of phosphate and calcium-containing pigments can ensure efficient corrosion protection on a par with chromate pigments due to the formation of a phosphate film with high barrier properties on a metal. Translated from Fizyko-Khimichna Mekhanika Materialiv, Vol. 36, No. 3, pp. 112–114. May-June. 2000.     

Influence of the conversion coating on the corrosion of galvanized reinforcing steel

Galvanized reinforcing steel with a cerium conversion coating have been studied in Ca(OH)₂ saturated solution with and without chlorides. Electrochemical results reveal that cerium conversion coating provides an effective corrosion resistance compared to galvanized steel at short immersion times, 5 days without Cl⁻ ions and 2 days with Cl⁻ in the solution. The results suggest that cerium layer inhibits hydrogen evolution on the galvanized coating at early stages. At longer immersion times, galvanized steel with cerium conversion coating and galvanized steel describe similar corrosion behaviour in both electrolytes. There is not significant differences in the corrosion current density, about 5 μA/cm², due to the presence of chlorides ions in the Ca(OH)₂ saturated solution up to approximately 17 days of immersion. At longer immersion times, from 30 to 50 days, specimens in the chlorides containing solution exhibit higher corrosion activity than that recorded in the free Cl⁻ solution revealing that cerium layer cannot inhibit the localized attack promoted by chloride ions.     

陶瓷转化工艺在空调镀锌钢板涂装中的应用

介绍一种新型陶瓷转化工艺在空调镀锌钢板的粉末喷涂中的应用.通过转化膜的晶相、附着力及盐雾试验表征,对预转化板的现有工艺进行控制.盐雾试验结果表明,预转化镀锌钢板经过弱碱性脱脂剂清洗,经陶瓷转化后与粉末涂料结合,可以得到良好耐蚀性和附着力强的膜层.     

热镀锌钢表面硅烷/硅酸盐复合膜的耐蚀性能研究

为了改善硅烷膜的耐蚀性,将硅烷化热镀锌钢板用硅酸钠溶液封闭后处理,获得了硅烷/硅酸盐复合膜.采用中性盐雾试验(NSS)、湿热试验、盐水全浸试验和电化学交流阻抗谱(EIS)评价了膜层的耐蚀性能.结果表明,与单一硅烷膜相比,复合膜的耐蚀性能明显提高,超过了常规铬酸盐钝化膜.尤其是在5%NaCl溶液中,复合膜的低频阻抗数值随浸泡时间的增加先增大后减小,表明其具有一定的"自修复"能力.