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Probably because the atmospheric corrosion of metals is always associated with the presence of water, the idea of using water‐borne coatings to give protection against corrosion has still not achieved general acceptance. Despite the considerable quantities of aqueous solution primers used in car body dip tanks, there remains a fairly deep‐rooted suspicion of aqueous primers. This may be due to the fact that with all other anti‐corrosive coatings the metal surface must be clean and dry, while aqueous systems inevitably wet the surface.

SEVERE natural exposure and laboratory test, dry salt/humidity, have both shown the advantages of primers that leach chromate over similar primers that do not. This advantage, applicable to both primer only and primer plus finish schemes, is paticularly evident where there are breaks, in the paint film due to edges, damage or paint cracking round rivet heads Several other laboratories have used other tests and have reached the same general conclusions. Sufficient experimental work has been carried out to formulate primers with very different leach rate characteristics. Many of these have been produced and are now being corrosion tested When the results are available it is hoped that they will be sufficiently consistent to enable a leaching test to be included in some paint specifications instead of the present two year corrosion test. Until then it is suggested that this fairly simple test provides a useful means of screening new primers for the paint industry and, for the aircraft constructor, one possible way of chuosing between the several competitive schemes offered to him, without having to wait many years for the results of corrosion lasts.

An abridged version of the final report by the Paint Research Association on Department of the Environ‐ment Contract CR10184

The performance of different pretreatment‐primer systems for hot‐dip galvanized (HDG) and Galfan coated steel has been studied. The materials were pretreated with three pretreatment processes; an alkaline oxide pretreatment with either a chromate or a zirconium based post‐rinse, and a zinc phosphating pretreatment. After the pretreatment, the panels were coated with four commercially available primers. The chemically treated substrates were characterized by using ESCA and GD‐OES, and the cured paint films by using FTIR. Paint adhesion of primed panels was determined with a combined cross‐cut and impact test and also with the NMP test. Formability of the panels was tested by T‐bend test and corrosion resistance with a cyclic prohesion test. According to the prohesion test results, primed Galfan coated panels have better edge corrosion resistance than primed HDG panels. Test results also show that the effect of pre‐treatment is not as significant for the corrosion resistance as the effect of primer. However, in the case of zinc phosphated samples, excellent synergistics between the pretreatment and two of the primers was detected.

This review of developments places special emphasis on shipyard practices to obtain the best results from coatings commercially available though most of its conclusions are, of course, relevant to industry at large. The main criterion by which a shop primer should ultimately be judged is: ‘Does its use mean that the painting scheme applied later will give substantially better performance than if it had not been used?’ There are very good reasons, mainly related to questions of corrosion, why shop priming should be practised in spite of difficulties.

As technical manager for a large group of paint manufacturers and painting contractors, the author is able to evaluate blast primers from the viewpoint of both supplier and user.

The widespread use of zinc dust paints and their economic advantages compared with the traditional methods of protecting steel from corrosion were described by speakers from the USA, Japan, the Netherlands, Belgium, Norway and the United Kingdom at a symposium organised by The Zinc Development Association in London on 25 and 26 September. This, the newest method of applying metallic zinc coatings to steel, has grown enormously in popularity during the last 10 years and has found many spectacular applications, such as for coating oil tankers of over 300,000 tons deadweight, oil and sulphur rigs in the Gulf of Florida, off‐shore oil drilling wells in Alaska, as well as for the more routine protection of bridges, railway rolling stock and the steelwork of chemical and other industrial plants. The symposium, which was attended by 300 people, mainly from the steel using industries in Britain and from the Continent, was the first of its kind at which users and suppliers of zinc dust paints and specialist consultants have been brought together to discuss the latest developments in zinc dust paints. Much interest was shown in descriptions of satisfactory methods of welding steel coated with zinc‐rich paints, and the simple ways in which health hazards from zinc fumes arising from welding can be avoided. It was stressed in several papers that zinc dust paints require good surface preparation, carefully controlled application and properly engineered overcoating, but the comparatively high initial cost of achieving this is amply repaid in reduced maintenance in subsequent years. The ZDA is preparing a full, illustrated report on the seminar which will contain the texts of the papers and an edited account of the discussions. This report will be sent to all who took part in the seminar and further copies will be available in a few weeks from the ZDA, 34 Berkeley Square, London.

The object of this article is to disclose the results obtained from a programme of work studying the use of zinc‐rich paints as primers for painting systems to be exposed to marine immersion. This programme was commenced early in 1963 with a view to deriving information on the way these systems functioned and hence to establish a code of practice which would enable personnel responsible for the protection of marine structures to obtain the best results with systems based on these primers.

In this special feature details are given of those British paints which can be described as corrosion‐resistant primers, both one‐ and two‐pack. The materials are generally classified according to the base or pigment which actively prevents corrosion—e.g. metallic zinc in zinc/epoxy formulations— or by the base which produces a barrier action against corrosion, e.g. bitumen in bituminous paints. Exceptions to this are the etching primers, which are separately classified. About 300 primers are described, the manufacturers' names and addresses being cross‐indexed and listed separately on page 48.

Repainting aircraft is a laborious and time‐consuming process, involving stripping, surface preparation and then painting. It is possible to distinguish two different systems for aircraft re‐painting, owing to their prime application area, referred to as the “European System” and the “USA System”. Examines these two systems and discusses the health and environmental aspects, along with their level of corrosion protection. Examines the properties of a new binder system, referred to as the KETAC‐System. As a result of the formulation of this new binder a new primer system was developed. The development of this primer , known as Aviox CF Primer, was carried out in close co‐operation with KLM Royal Dutch Airlines, the results of which are reviewed.