PRINCIPLES OF CORROSION OF METAL CONTAINERS 29 complexing nature of the tin ion, it is usually effectively below. One approach to this is to put something into your solution which will complex tin and lower its potential. For aluminium containers the question is somewhat more complex, because it is hard to forecast at which site of the container one will obtain pin-holes. They occur at active points, and we do not really know what causes these: it could be impurities in the aluminJure, proximity of another metal, or perhaps other effects. MR. J. M. BLAKeWAY: We have experienced corrosion in aerosol cans with hair- spray formulations and I wonder to what extent your tests can be used as a test for screening possible passivators, or possible antioxidants which might work in relatively small portions in the formulations. Is it a possible approach to the problem? T• L•CTUR•R: A formulation (such as hairspray) can be taken and small amounts of various inhibitors added. These can be organic or inorganic, but the former is the most likely for a hairspray. Corrosion rates caused by different types, and levels, of inhibitor can then be compared, and the most favourable selected from the point of both bimetallic corrosion and direct attack. The effect of other variables, such as water concentration, can also be assessed. MR. T. A. BRocK: Some years ago I was associated with a hair spray where the container which was intended to be used was perfectly satisfactory in the preliminary screening tests. When the product went into bulk manufacture a very high per- centage of the cans developed pin-hole corrosion after a very short time. At that time, the container manufacturer suggested that perhaps the cans that were used in the test had aged, and an oxide film had developed on the surface of the aluminium, whereas the ones used in production were straight off the fabricating lines, and there- fore did not have the chance to develop this protective oxide film. Would you like to comment? T• Luc'ruR•R: This argument can be applied both ways. It can also be said that if a large area of oxide film was present this would act as a large cathodic area and pin-hole corrosion could occur at the places where the film was not complete. A more likely explanation of this would be based on the difference in the oxygen content of the test and production cans. An aerosol storage test is not realistic unless it can be filled on a production line, and you get the sanhe purging conditions as you will in practice. In the laboratory these conditions could be quite different, and they are usually better than on the production line. If the purging conditions in the laboratory were very good and there was more oxygen in the production cans this might be enough to cause corrosion. MR. E. K. CLARKe: HOW do you measure potentials and currents in an aluminium container? If one is thinking of using an aluminium container with an aluminium cup a single metal system results. T}m L•CTUR•R: We have done much less work on aluminium than tinplate, mainly because we use far more tinplate containers than aluminium. A relevant test in this case is to look at the direct attack on aluminium by polarisation resistance measurements. Unfortunately this does not take into account the possibility of pin- hole corrosion of aluminium which is rather a special problem, as the origin of active anodic sites leading to the incidence of pin-holes is sometimes uncertain.

J. Soc. Cosmetic Chemists 20 31-48 (1969) ¸ 1969 Society of Cosmetic Chemist• of Great Britain The influence of the Weights and Measures Act on the packaging scene K. G. JOHNSON* Presented at the symposium or• "Technical developments in cos- roetics packaging", organised by the Society of Cosmetic Chemists of Great Britain, at Harrogate, Yorks., on 26th March 1968. Synopsis--This paper contains a brief summary of those parts of the Weights and Measures Act (1963) relevant to cosmetics, examines the requirements placed upon cosmetic manu- facturers, and the factors that may be considered in packaging and plant design as a result of the Act. With the introduction of the Weights and Measures Act (1963), cosmetics and toiletry articles first came under legislation in this field. As with any new Act, there are many facets with a degree of ambiguity as to precisely what is permitted or what is not. There are also many parts of the Act which do not leave any doubt as to their interpretation. As to the ambiguous parts, •ve as manufacturers can only take advice from our legal advisers or local Weights and Measures officers. None of us as yet are experts and, in fact, if these exist they are probably magistrates or Appeal Court .Judges who will at some stage in the future be called upon to make decisions which will translate the Act into la•v. T• w•zm}•Ts ^NI) •m^SUI•S ACT (1963) The Act lays down that subject to certain exemptions, in any retail sale by quantity, or purporting to be by quantity, the quantity shall be *Beecham Products (U.I(.), Maidenhead, Berks. 31