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[0168] The data shown in Table 2 illustrates the results of XPS analysis for the amount of aluminum metal and carbon on the can surface following the various treatments. The amount of carbon can serve as a surrogate measure for the presence of contaminants (e.g. smut). A higher aluminum/ carbon ratio as indicated in Table 2 thus indicates that more aluminum is present on the can surface and that more carbon or contaminant residue has been removed. All of the cans treated with the polymeric particles (i.e. cans 4 to 7) show an increase in aluminum/carbon ratio compared to the controls ( cans 1 to 3) demonstrating an improved cleaning efficiency. A considerable increase in cleaning performance is shown for cans 5 and 7 which each further include citrate and a non› ionic surfactant in the formulation. In addition, a significant enhancement in cleaning performance was noted for can 6 which comprised treatment with polypropylene polymeric particles and water only. 

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[0169] The data shown in Table 3 illustrates the results of XPS analysis for the amount of aluminum oxide and alumi› num metal on the can surface following the various treat› ments (note that verified data for can 6 and can 7 was obtained for cleaning efficiency only). The thickness of the aluminum oxide layer was also calculated in accordance with the stan› dard methods outlined in B. R. Strohmeier, Surf. Interface Anal. 1990, 15, 51 and T. A. Carlson, G. E. McGuire, J. Electron Spectrosc. Relat. Phenom, 1972/73; 1, 161. As shown by the results for can 5, treatment of the can with nylon 

beads, water, citrate and the non-ionic surfactant demon› strated a significant decrease in the aluminum oxide area (%) and a significant increase in the aluminum metal area (%) for the surface of the metal substrate compared to the controls (i.e. cans 1, 2 and 3) and compared to the treatment with nylon beads and water alone (can 4). Furthermore, an aluminum oxide layer of significantly reduced thickness was obtained for can 5 (5.36 nm) compared to the controls and when compared to the treatment with nylon beads and water. 

## Aluminum Cleaning & Oxide Removal Using an Apparatus Fitted with Pumping Means 

[0170] The ingredients were Mulan™ 200S (25.0 g), a non-ionic surfactant supplied by Christeyns, Bradford, UK and the citrate component consisted of trisodium citrate dihy› drate (500.0 g) supplied by VWR, Loughborough, UK. The polymeric particles were Nylon 6,6 grade Technyl™XA1493 supplied by Solvay, Lyon, France in the form of beads. The mass of the polymeric particles used in the apparatus was 10 kg. Uncoated aluminum metal cans grade ALJSC60ML63X15 were supplied by Invopak UK Ltd. Hyde, Cheshire. 

[0171] XPS analysis was carried out with an Axis Ultra DLD, using an Al ka monochromated radiation source. An overall survey scan was taken initially, followed by detailed scans of the main peaks for the elements identified, using a pass energy of 160 eV and 20 eV respectively. The measured data was fitted using Casa XPS (Casa Software Ltd, UK), using relative sensitivity factors based upon the scheme where Cls=l, and adjusted to correct for any minor charging using the aliphatic carbon peak at 285 eV. Each sample was measured in 2 places. 

[0172] In order to carry out the experiments, the treatment liquor was added to a vessel containing a pump. The treatment liquor consisted of the polymeric particles (of total mass 10 kg) and tap water (45 kg) and the further formulation com› ponents as shown in Table 4. Aluminum cans were fixed to a metal rod which was fixed by means of a clamp. Each can was inserted into the vessel containing the treatment liquor. The cans were then subjected to contact with the pumped liquor for a period of30 minutes at a temperature of22° C., ensuring contact between the can and the treatment liquor. After treat› ment, the cans were washed with Milli-Q™ water and iso› propanol and subjected to XPS analysis. 

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## Experiment 2 

