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The purpose of this work was to study the cracking susceptibility of a 7017 aluminium alloy, after anodising under various conditions.

Slow strain tests in dry air, laboratory air and sodium chloride solution were employed. Anodic oxide films were produced with various applied current densities and thicknesses, in horizontal or vertical orientation of the coatings, at the free corrosion potential and also at various anodic or cathodic potentials. For the interpretation of the results, a metallographic study of the specimens before and after straining to failure was carried out using a scanning electron microscope.

The behaviour of anodic coatings was found to depend very much on the anodising conditions. The coatings reduced the ductility of the alloy in dry air but can actually increase the ductility in laboratory air and in 3.5 per cent sodium chloride solution. In most cases, the ductility of coated specimens was greater in 3.5 per cent NaCl solution than in dry air, possibly due to crack blunting by the aggressive environment. Anodic coatings moved the free corrosion potential of the alloy in the noble direction and both the anodised and the bare alloy generally suffered a reduction in ductility at potentials anodic or cathodic to the free corrosion potential, the fall being more rapid for the anodised alloy.

The mechanism causing the increased ductility of coated specimens in 3.5 per cent NaCl solution than in dry air remains yet to be confirmed.

The selection of suitable anodic coatings for the protection of aluminium alloys against stress corrosion cracking depends on the anodising conditions.

The paper provides information regarding the influence of anodising conditions on the anticorrosive properties of electrolytically prepared anodic coatings on aluminium alloys.

The purpose of this paper is to study the stress corrosion cracking (SCC) behaviour of anodized 1050 Al‐alloy in marine environments at different concentrations of sulphate ions.

The SCC experiments were performed by measuring the time to failure in 3.5% NaCl solution, or in the presence of three different concentrations of sulphate ions under conditions of applied anodic current. For the interpretation of the results, changes in potential during SCC tests and optical microscope micrographs of stress corrosion tested specimens at various periods of time, were obtained.

The influence of seawater composition on the SCC behaviour of the anodized 1050 Al‐alloy depends on the concentration of sulphate ions, the oxide thickness and the stress level. At the higher stress levels and low concentrations of sulphate ions, increased times to failure were observed. These results were attributed to the inhibitory action of sulphate ions. At a low stress level and higher concentration of sulphate ions, the increased times of exposure and the more intensive corrosive environment led to partial destruction of the anodic coatings and a decrease in the time to failure. Better protective properties were observed at an oxide thickness of 10 μm. The thicker oxides did not protect so well because they were more brittle, cracking under strain and allowing corrosive species to reach the metal surface.

The hypothesised mechanism of the effect of seawater composition on the SCC behaviour of anodized Al‐alloys depended on the concentration of sulphate ions and the stress level remains yet to be confirmed.

The selection of suitable anodic coatings for the protection of aluminium alloys against stress corrosion cracking depends on the composition of the marine environment.

The paper provides information regarding the influence of sulphate ions on the anticorrosive properties of electrolytically prepared anodic coatings on aluminium alloys.

Increasing utilisation of the properties of hardness, corrosion resistance and electrical insulation has taken place rapidly in recent years. Still scope exists for further development of anodised aluminium as knowledge of the mechanism involved grows. In the first of this two‐part article the author deals mainly with bright and conventional architectural anodising.

While there is an increasing use of anodised aluminium for some applications in swimming pool buildings, there is considerable reluctance in accepting it for general use, because of a mistaken belief that the chlorine‐containing atmosphere will cause corrosion of both mill finish and anodised aluminium.

Friction arises at the real contact area of two contacting bodies. This area depends on the mechanical properties of the bodies, geometrical configuration, and load. The authors described a new optical method of determining the area of contact, developed in the Laboratory of Friction and Friction Materials of the Academy of Sciences, Russia. This method is based on reflection and diffusion of rays of light from transparent samples when passing out of one transparent medium into another having a different coefficient of refraction. The light ray passes through the contact surface without reflection only if it falls strictly perpendicularly on the surface. Owing to this, rough surfaces diffuse light and its brightness diminishes. When light passes through two surfaces of transparent bodies, the degree of diffusion becomes even greater. In places of contact of the two surfaces the interlayer of air disappears and the ray passes directly out of the one body into the other. If the two bodies have the same refractive index, the ray does not deflect from its path and no loss of intensity results.

The purpose of this paper is to study of the effect of carboxylic acids additions to the anodising bath on the subsequent corrosion and stress corrosion cracking (SCC) tendencies of anodised 1050 Al‐Alloy in 3M NaCl solution.

The study was carried out using SCC tests and electrochemical cyclic potentiodynamic measurements at a high or a slow scan rates. The anodic coatings were prepared electrolytically in a bath of 4 M H2SO4, with and without additions of 0.015 M oxalic, malonic, tartaric, maleic, or citric acids. The consequent thicknesses and packing densities of the coatings were measured.

The SCC behaviour was found to vary with both anodising conditions and stress level. The addition of carboxylic acids in the anodising bath increased the protective properties of the coating. In corrosion conditions without stress, the addition of the carboxylic acids decreased the susceptibility to pitting corrosion, the effect depending on the presence or absence of corrosion products. The addition of the carboxylic acids during anodising leads to the formation of less porous and more compact oxide layers and increases the anticorrosive properties of the coatings. The benefits were most pronounced for the coating prepared in the presence of maleic acid.

The belief that the effect of carboxylic acids on the corrosion and SCC behaviour of Al‐Alloys is due to the absorption of these compounds on the metal surface and the formation of complexes on it, depending on the structure and carbonic chain of these compounds, remains yet to be confirmed.

Anodic coatings prepared in an electrolytic bath containing carboxylic acids can be used for the protection of aluminium alloys against corrosion.

The paper provides information regarding the improvement of the anticorrosive properties of electrolytically prepared anodic coatings on aluminium alloys.

The Conference on Anodised Aluminium, organised by the Aluminium Development Association and held in the new Cripps Hall at Nottingham University from September 12–14, was probably the first of its kind in the world and attracted nearly 300 delegates. Eighteen papers were discussed. In the following pages abstracts and conclusions from most of the papers are given, emphasis being placed on the corrosion aspects of the subject.

Anodizing is used widely in the surface treatment of aluminium alloys for aerospace applications. Considers recent advances in understanding of the influences of alloying elements in anodizing of aluminium alloys and, in particular, their applicability to second phase particles during anodizing of commercial alloys. Through more precise knowledge of the response of second phase materials to anodic polarization, improved anodizing and related surface treatment processes may be developed in order to enhance the performance of aluminium alloys.

The purpose of this paper is to join an anodized aluminium alloy AA6061 sheet with high-density polyethylene (HDPE) using friction spot process.

The surface of AA6061 sheet was anodized to increase the pores’ size. A lap joint configuration was used to join the AA6061 with HDPE sheets by the friction spot process. The joining process was carried out using a rotating tool of different diameters: 14, 16 and 18 mm. Three tool-plunging depths were used – 0.1, 0.2 and 0.3 mm – with three values of the processing time – 20, 30 and 40 s. The joining process parameters were designed according to the Taguchi approach. Two sets of samples were joined: the as-received AA6061/HDPE and the anodized AA6061/HDPE.

Frictional heat melted the HDPE layers near the lap joint line and penetrated it through the surface pores of the AA6061 sheet via the applied pressure of the tool. The tool diameter exhibited higher effect on the joint strength than processing time and the tool-plunging depth. Specimens of highest and lowest tensile force were failed by necking the polymer side and shearing the polymer layers at the lap joint, respectively. Molten HDPE was mechanically interlocked into the pores of the anodized surface of AA6061 with an interface line of 18-m width.

For the first time, HDPE was joined with the anodized AA6061 by the friction spot process. The joint strength reached an ideal efficiency of 100 per cent.

The purpose of this study was to investigate the effect of electrolyte compounds on the anodizing process. Magnesium and its alloys have low corrosion resistance. Anodizing operation is performed to increase the corrosion resistance of magnesium. Anodizing solution compounds have a great effect on the oxide coating formed on the substrate. The effect of anodizing electrolyte composition on the corrosion behavior of magnesium was investigated in the simulated body fluid.

Three pure magnesium samples were anodized separately at 15 min, a constant voltage of 9 volts and room temperature. Three different solutions were used, which are the anodizing solution by the Harry A. Evangelides (HAE) method, the sodium hydroxide solution and the anodizing solution of the HAE method without potassium permanganate. Field emission scanning electron microscope (FE-SEM) was used to examine the surface of the anodized oxide layer and electrochemical impedance spectroscopy (EIS) was used for electrochemical corrosion evaluations.

The results of corrosion tests showed that the sample anodized in the solution without potassium permanganate has had the highest corrosion resistance. Also, microscopic images showed that the surface of the oxide layer of this sample had a uniform structure and is somewhat smooth. It seems that in the anodizing process by HAE method at 9 volts and for 15 min, the absence of potassium permanganate improves the corrosion resistance of magnesium. Also, anodizing in HAE solution gives more positive results than anodizing in sodium hydroxide solution.

The solution without potassium permanganate was studied for the first time and also the effect of these three anodizing electrolytes was compared together for the first time. Effect of anodizing at 15 min and constant voltage of 9 volts. Sample’s electrochemical behavior in the body's simulation environment has been investigated. Improvement of electrochemical properties in the solution of the HAE method without potassium permanganate.