混合稀土对工业纯铝冲压性能的影响

对稀土质量分数不同的稀土铝合金与不加稀土元素的工业纯铝进行对比实验,研究稀土质量分数及不同的热处理状态对合金冲性能的影响,探讨了不同使冲压性能,同时对稀质量分数不同的铝合金的硬度和耐蚀性进行了研究。     

Carbonyl compounds as corrosion inhibitors for mild steel in HCl solutions

The paper gives an account of the performance of a number of carbonyl compounds as corrosion inhibitors of mild steel in 1–6 N solutions of hydrochloric acid. Furfuraldehyde seems to be the best inhibitor of all the carbonyl compounds investigated. Activation energies in the presence and absence of inhibitors have been evaluated. In cathodic protection studies furfuraldehyde reduces the protective current density considerably. The difference effect is positive in the absence and presence of inhibitors. Galvanostatic polarization data indicate that all these compounds are predominantly cathodic inhibitors. These substances are more effective in preventing the corrosion of aluminium alloys in hydrochloric acid solutions than the corrosion of mild steel.     

Corrosion inhibition with rare earth metal salts

Owing to the toxic and carcinogenic nature of the most common corrosion inhibitor, the chromate ion, considerable effort has been directed towards developing other environmentally acceptable inhibitors. Extensive research at ARL and elsewhere has shown that the soluble rare earth metal (REM) salts are effective inhibitors of the corrosion of aluminium alloys, steel and zinc. This paper will review experimental studies in which REM salts have been used as corrosion inhibitors, and will discuss the inhibition mechanisms involved.     

Cerium-based conversion coatings on aluminium alloys: a process review

Abstract

Rare earths are among the most promising options for replacing chromate conversion coatings on aluminium. In nearly three decades of research, several hundred papers have been published in the area, the bulk of which has never been reviewed. This paper reviews the literature on rare earth coating processes, with particular emphasis on those based on cerium. It is concluded that several process areas are poorly understood, some of which are critical to further progress in the field. These include the development of industrially suitable pretreatments, technologies for coating non-aerospace alloys and seals to enhance corrosion performance and paint adhesion.     

Galvanic corrosion of aluminium alloy members of bridge guiderails under severe atmospheric exposure conditions

ABSTRACT

Aluminium alloys are nowadays preferred as materials for bridge guiderails especially for bridges connecting oceanic islands or spanning inlets due to their inherent corrosion resistance. But because of the limited mechanical strength of aluminium alloy, fasteners of guiderail members are made from steel materials. It has been found that contact between bare steel fasteners and aluminium alloy members can cause galvanic corrosion in the aluminium alloy. Research was carried out to investigate the capability of different surface treatments on fasteners and aluminium alloy members to inhibit galvanic corrosion under atmospheric exposure for periods of one and three years. It was found, among other results, that stainless steel fasteners treated with zinc flake coating were the most effective inhibitors of galvanic corrosion on aluminium alloy members.     

Five-year corrosion of aluminium alloys at several marine sites

Abstract

Eight aluminium alloyswereexposedat marine sites at Kure Beach, North Carolina; Arenzano, Italy; and Bohus-Malmon, Sweden. Panels were removed at the end of 1-, 2- and 5-year exposure periods and evaluated for depth of pitting, corrosion rate and loss of mechanical properties. The high-purity aluminium and certain aluminium–magnesium alloys showed the lowest corrosion rates based on weight losses. The site at Arenzano generally was most severe as regards depth of pitting and weight loss with the Kure Beach, North Carolina, 80-foot lot being next in severity. Both pit-depth growth and corrosion rate decreased with exposure time for all alloys and locations. Several alloys, at the more severe sites, showed some decreases in some mechanical properties as measured by elongation of tensile specimens,but these changes are not of such magnitude as to be structurally significant.

Aluminium–magnesium alloys 5050, 5052, 5086 and 5154 are among the best for use in marine environments. The structural alloy 6061 is also highly satisfactory for marine atmospheres. A maximum pit depth for all alloys of about 15 mils was found after five years at Arenzano and about 9·5 mils for the same period at Kure Beach 80-foot lot.     

Some aspects of the performance of rare earth modified nickel-base alloys in hot corrosion conditions

Rare earth additions have shown improvements to corrosion behaviour of nickel and cobalt base superalloys in simulated fuel combustion corrosion situations. “Hot corrosion”tests, at various levels of severity, have been conducted on nickel-base alloys in the range of 870 to 1200°C with sulfur supplied from molten sodium sulfate or from low concentrations of sulfur dioxide in argon (0.2% SO₂). The results show, that rare earth as oxide is essential for corrosion resistance in sulfurous environments.     

Aluminium in fresh waters

Abstract

The paper summarises research at these Laboratories on corrosion of aluminium in fresh waters. The type of corrosion affecting aluminium depends on water composition. Deep pitting requires oxygen, chloride, carbonate hardness and copper, but the higher chloride contents encourage more general corrosion. Higher carbonate hardness reduces the number of pits formed; sulphates have a similar effect and also increase pit depth. Except in waters of very high copper content, attack is generally less at elevated temperatures. Different alloys differ only slightly in resistance to attack. On superpurity aluminium, pits are slow to form but subsequently penetrate at the same rate as in SIC type. The best form of protection for aluminium is cladding with aluminium– l¼% zinc. This prevents pitting of N3 sheet or tube even in highly corrosive hard waters. Spraying with aluminium–zinc or anodising is also effective. Treatment to form boehmite films gives some protection but is ineffective in the more corrosive waters.     

Laser beam welding of wrought aluminium alloys

Abstract

Laser beam welding is now a common manufacturing method for a wide range of steel products from automobiles to razor blades. However, the process has only recently been approved for critical applications involving aluminium alloys, notably in the aerospace and automotive industries. The properties of aluminium alloys influence the interaction between the beam and the material to a far greater extent than for steels. The challenge of developing industrial welding procedures has therefore been considerable. The present review describes the effects of CO₂ and Nd–YAG laser beam processing parameters and the properties of the most common wrought aluminium alloys on the characteristics of welded joints. Porosity, solidification cracking, and poor weld bead geometry are shown to be the most frequently encountered imperfections. These can be eliminated through the use of appropriate filler materials, process gases, material preparation, and in some instances, adaptive control systems. Very little work has been reported on the corrosion properties of laser welded aluminium alloys. Experimental processing parameters are presented and compared using an analytical model, which can also be employed for predictive purposes. A number of industrial applications are described. These demonstrate that, for specific alloys, the process is now sufficiently well understood to be approved for high volume production, particularly in the transport industries.     

Failure of aluminium metal spray/organic duplex coating systems on structural steel

Abstract

Individually, aluminium metal spray (AMS) and organic paints are well established as effective protective coatings for steel substrates. These coatings are also frequently used together as duplex systems where their combination should produce a synergistic effect. However in certain, mainly marine, environments premature failure of such coatings, involving early blistering of the paint, has been observed in service after 3–5 years. This work aims to understand the mechanisms associated with the early failure of the AMS+paint duplex system. Various panels were initially prepared for accelerated exposure using combinations of coatings on blast cleaned steel. Visual inspection after salt spray exposure revealed the presence of white corrosion product, which was confirmed afterwards as Al(OH)₃. Observation of the coating microstructures before and after salt spray exposure confirmed significant local corrosion of aluminium underneath the paint layer. It is suggested that failure of the duplex AMS/paint system initiates by corrosion of the porous AMS underneath the organic layer then progresses by the combined effect of volume expansion due to formation of Al(OH)₃ and cathodic blistering of the paint from the AMS surface.     

Boro-aluminising of P91 steel by pack cementation for protection against steam oxidation

Abstract

High performance alloys are often the materials used for various components exposed to high temperature environments. In many cases, protective coatings are applied in these alloys, providing higher corrosion and oxidation resistance, compared to the base material. This study investigates the feasibility to apply boro-aluminising treatment on P91 steel by pack cementation process, to increase the steel high temperature properties in oxidising and corrosive environments. Packs activated by AlCl₃, NH₄Cl and KBF₄ were used to carry out the coating deposition at a temperature of 715°C for 6 h. The coating formed was analysed by means of SEM and XRD, and the compounds formed were identified. Cyclic steam oxidation for a total of 1008 h at 650°C revealed an oxide scale of 50 μm for the uncoated P91 steel, while the coated steel shows practically no oxidation effect.     

稀土在镁合金腐蚀防护中的应用

综述了镁合金的腐蚀特性与防护措施，介绍了稀土在镁合金腐蚀防护上的应用，探讨了稀土对镁合金耐腐蚀性能的影响作用.     

Beschichtungssysteme für Verbindungselemente in Kontakt mit Leichtmetallen

Coating systems for joining elements in contact with light metals Galvanic corrosion of light metal alloys can only be avoided, if the steel fasteners are given an electrochemically compatible protection or if the corrosion circuit is interrupted by electric insulating layers. Current density vs. potential curves of chromated zinc alloy coatings show, that by means of zinc nickel coatings a largely electrochemical adaption to the equilibrium potential of quenchaged aluminium alloys of the type AlMgSi is possible. On the other hand, the equilibrium potentials of chromated systems based on ZnFe, ZnCo respectively, are too low to avoid galvanic corrosion on aluminium. In practicerelated corrosion tests on joining elements, this result was confirmed. Besides this, zinc- and aluminium-bearing sintersystems, galvanic tin depositions as well as ternary mechanical coatings based on ZnSnAl have been proved to be compatible with AlMgSi-type alloys. For coating systems in contact with magnesium a satisfactory protection against galvanic corrosion can be achieved effectively with insulating top coats. The results with suitable duplex systems are presented and recommendations for practical applications are derived.     

Corrosion and corrosion prevention of magnesium alloys

Introduction of high purity alloys improved the corrosion resistance of magnesium alloys significantly. This has led to an increased use of magnesium for components like valve covers, transmission housing, and gear box housing. Because of the unnoble nature of magnesium, galvanic corrosion is the main challenge when magnesium is used in corrosive environment. By proper material selection, proper design and selective use of coatings and insulation materials, the risk for galvanic corrosion is significantly reduced. Test results show that fasteners made of aluminium of the 6000 series reduce galvanic corrosion of magnesium to very low levels in salt spray tests. Combinations of plated steel fasteners and aluminium washers are very efficient for galvanic corrosion prevention. Furthermore, it seems that sealed zinc plating is the best type of plating for steel fasteners. The plating must, however, be free from defects and the bolt head design is an important factor to get a high quality plating.     

Influence of climatic factors in cyclic accelerated corrosion test towards the development of a reliable and repeatable accelerated corrosion test for the automotive industry

Two designs of experiments made of nine accelerated tests each were used in order to study the influence of a selection of important climatic parameters such as the concentration of NaCl, the drying level, the basic humidity cycle, the frequency of salt spray and the temperature. The accelerated corrosion tests were all performed using automatic chambers. Different automotive materials were selected in order to study the resistance to cosmetic corrosion, perforation corrosion and bi‐metallic corrosion. For cosmetic materials, coated panels of cold rolled steel (CRS), zinc‐coated steel and aluminium alloys were chosen. Perforation corrosion was investigated using crevice panels of CRS, zinc‐coated steel or different grades of aluminium alloys. From the results, the influence of testing conditions on the cosmetic and perforation corrosion of different automotive materials was obtained. As an example, it was shown that an elevation of the temperature from 35 to 45 °C in the cyclic corrosion test increased the scribe creep on painted CRS and aluminium alloys while it has no significant effects on painted hot dip galvanized (HDG) panels. The results were also compared to that obtained after 2 years of exposure at a marine exposure site and on busses driving in area using de‐icing salt. It was shown that one of the tests performed gives a good correlation to field results.     

Bimetallic Corrosion Effects on Mild Steel in Natural Environments

Abstract

Corrosion rates of mild steel when coupled to each of 31 other metals and alloys have been determined in 5 natural environments using disc-type specimens. These environments were industrial, urban/rural and marine atmospheres, natural water and sea water. The relative order of effect on the corrosion rate of mild steel in each environment has been tabulated. The results show that the performance of mild steel in a given couple can differ appreciably in different environments.     

含稀土镁铝系合金耐腐蚀性能的研究现状

镁铝系合金是目前最常用的商业材料之一,但由于合金的耐蚀性能较差,因此对合金的耐蚀性研究具有重要意义。本文综述了稀土在镁铝系合金中的存在形式以及含稀土镁铝系合金在国内外的研究现状,讨论了稀土对合金耐蚀性的影响机理。     

稀土铝合金热浸镀渗工艺研究

对稀土铝合金的热浸镀渗工艺及渗铝后的耐腐蚀性进行了研究。结果表明，稀土对于热浸镀渗铝具有良好的催渗作用。钢表面热浸镀渗稀土铝后，具有良好的耐腐蚀性，其中含0．3％LPC混合稀土的铝合金具有更好的耐腐蚀性，其耐腐蚀性3倍于纯铝。     

富Y重稀土对ZM5合金组织和性能影响的研究

以ZM5镁合金为基体材料，以富Y重稀土为添加原料，应用铸造方法制备了稀土镁合金。利用光学金相显微镜（OM）、X衍射分析、拉伸试验和腐蚀试验等方法，考察分析了稀土Y对ZM5合金铸造组织结构、力学性能和腐蚀性能的影响。结果表明，铸态合金中出现了新相Al3La、MgY，它对于减少晶界处第2相的析出、晶粒的细化以及力学性能的提高起着积极作用。同时，稀土的加入明显地改善了合金的腐蚀性能。     

Atmospheric corrosion of Mg–rare earth alloy in typical inland and marine environments

The atmospheric corrosion behaviour of peak aged Mg–5Y–7Gd–1Nd–0·5Zr alloys in typical land (Beijing) and marine (Qingdao) environments were investigated by optical microscopy, SEM and X-ray diffraction. The weight loss rates and residual mechanical properties were analysed. The atmospheric corrosion rates of specimens in a typical marine environment were higher than those in land environment. The results demonstrated that temperature, relative humidity and inorganic salts at field exposed sites played an important role in atmospheric corrosion behaviours. The results of our investigation may find wider applications for Mg–rare earth alloys in atmospheric environments.