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Aluminium is being increasingly used in refinery construction. Applications range from storage tanks to moisture‐proofing pipe insulation; from heat exchangers to structural elements. The main reasons for this are its good resistance to many types of corrosion, low weight, low cost per unit volume, high thermal conductivity, non‐magnetic and non‐sparking characteristics, good reflectivity and good appearance. From the design engineer's point of view, the metal has the further advantages of good workability and high strength in its alloys. The author describes some of the current practices and experiences in the U.S.A.

Two types of aluminium alloys, 2024‐T3 and 7075‐T6, having been selected, this study aims to investigate the effect of metallurgical aspects on intergranular corrosion.

To determine and evaluate the metallurgical effects of heat treatments on corrosion behaviour of these alloys, G67 ASTM test was selected.

The results showed that with increasing the aging time in aluminium alloy type 2024‐T3 the susceptibility to intergranular corrosion increases, while in type 7075‐T6 with increasing aging time the intergranular corrosion rate remains nearly unchanged.

As these results refer to precipitate the intermetallic compound phases, the amount of these phases increases with the increase of the aging time in both alloys.

The investigations showed that the phases that initiate in 2024‐T3 act as anode sites, while in 7075‐T6 they act as cathode sites.

At this stage I think that we can usefully give some detailed consideration to the copper‐aluminium alloys, and reference may in this connection be made to the equilibrium diagram shown in Fig. I, which, as in the case of the steels, gives an explanation of, and is a guide to, their behaviour and heat‐treatment.

THROUGHOUT the history of the advance of aviation the development of light alloys occurs and recurs as a silver thread, lightening the pattern. From the very first the possibility of aviation has been bound up with the design of the prime mover, and the remarkable strides made during the past two decades in the production of power from a minimum of weight are largely due to the alloys of aluminium, their strength and rigidity for a given weight, their thermal properties, and their capacity for prolonged, reliable service.

A review is made of existing and likely future aircraft materials and their choice for use on airframes is discussed in relation to the problems of advanced aircraft design. Both technological and production problems arc included and it is finally suggested that urgent governmental action is required to remedy Great Britain's grave lack of suitable capital equipment.

Summary This paper describes an electrochemical procedure useful to the determination of metallic and oxidised parts in zinc‐base coatings obtained by thermal spraying. The procedure has been successfully applied to the examination of coatings made of pure zinc or of a zinc alloy containing 15% in weight of aluminium, as well as on corroded as on uncorroded samples. The method allows the degree of advancement of oxidation in the coating to be determined as a function of the exposure time; this permits an evaluation of the corrosion resistance to be made without having to wait for the appearance of rust on the protected steel plate. By this manner, the better resistance of the studied alloy compared to the pure zinc has been evidenced under severe conditions of attack by an aerated 5% NaCl solution. This could be attributed to a decrease in the oxidation rate of the metallic zinc in the alloy, owing to its higher aptitude to self‐sealing. The improved behaviour of the alloy has been attributed to the existence through the whole thickness of the coating of a coherent network made of an α‐aluminium‐rich phase, this explanation being in good agreement with the results of other investigations carried out by SEM + EDAX or by X‐Rays diffraction techniques, which have been reported elsewhere. Each studied coating was obtained from wires produced by Vieille‐Montagne under the trade‐names Zinacor 100 (pure electrolytic zinc) and Zinacor 850 (zinc‐base alloy containing 15% aluminium).

ALUMINIUM in various forms is used very considerably in the aeronautical industry—even so far back as the end of the war it was computed that in the year 1918 the allied governments employed about 90,000 tons of aluminium and its alloys in aero construction. And it must not be overlooked that it is largely due to the special properties of these materials that the present amazing development of aircraft has become possible.

The discovery of the Hall‐Herqult process for the manufacture of aluminium made it possible to obtain the metal in large quantities. Soon it attained the position of a major industrial metal due to its lightness combined with strength, capacity to take up a high polish, excellent conductivity of heat and electricity. Moreover it gives a wide range of extremely valuable alloys with diverse elements such as copper, magnesium, nickel, silicon, zinc, etc.

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.

IN recent years several interesting and excellent papers have been read before various Societies, dealing with magnesium and its alloys.