326 JOURNAL OF THE SOCIETY OF COSMETIC CHEMISTS in about 3 cc (measured as liquid) of the propellant to be used, and immediately sealing the valves onto the containers. The propellant was pressure-filled through the valves. Twelve containers were stored, on their sides, at each of the conditions-- 1 ¸ 20 ¸ and 40øC. One container from 40 ø was examined after one week, and one container from each condition after one, three, and nine months. Further examinations up to two years will be carried out in due course. FORMULATIONS The formulations were all hairsprays, except for one test with Industrial 3/lethylated Spirits alone, and varied in type of resin, perfume, and denaturant. All were made up in such a manner that when the propellant was added, the water content of the system was less than 0.5%, except where added deliberately as indicated in the tabulated results. I•ESULTS As mentioned above, each cell was allowed to discharge for 24 hours while the current was measured. The graphs generally were very similar in shape, the current falling fairly quickly to a lower value than at the start, except with one or two very corrosive formulations (Fig. $) where an increase was found. In all cases, however, the current became fairly steady MIX 11/12

CORROSION IN ALUMINIUM CONTAINERS 327 after about 15 hours, and for that reason the reading obtained after this time was selected for comparison with the storage test results. The results of the corrosion cells and the storage tests are summarized in Table 1, and compared. Table 1 Prediction of suitability & rank in order of corrosion found on storage tests. Highest number is most corrosive. Pro- Cell -- Formula pellant Reading* 3 months at 40 ø in 9 months at 20 ø in 9 months at UNLACQUERED UNLACQUERED 20 ø in containers containers LACQUEREE containers I 11s 0.0 N 4 D 2 S 3 I 12 0.1 N 4 D 1 S 3 IMS 11/12 0.1 S 2 test stopped not tested II 11/12 0.1 S 1 N 3 S 1 I 11 0.2 D3 N4 N6 I 11/12 0.2 D 3 N 4 S 4 III 11/12 0.2 D 3 N 4 S 2 IV 11/12 0.1--0.4 S 2 D 1 N 5 IV + 11/12 1.5 N 6 stopped at N 7 Cetrimide 3 months IV + 12 2.6 N 6 stopped at N 7 Cetrimide 3 months I + 12 1.0--4.0 N 5 N 5 S 1 5% water III + 11/12 20.0 N 6 stopped at N 8, Cetrimide 3 months * 15 hour reading in MICROAMPERES from graphs. N--not suitable. D--doubtful. S--suitable. It can be seen that the graphs fall into two main groups, those with 15 hour readings up to 0.4 microamps, and those with readings over 1.0 microamps. The formulations can also be divided into two groups, those considered suitable for use in the containers used, and those unsuitable. A formulation was judged unsuitable if the container exhibited any pits.