The recycling of aluminum can is explained mainly from the stand point of closed-loop recycling that used beverage can (UBC) is returned to reproduce as a raw material of alloy for aluminum can. Since the energy from remelted aluminum by recycled UBC saves up to 95% of the over-all energy required for primary aluminum production, the economical effect is very large. If the recycling system does not act on an economical rule, it would be very difficult for us to realize the UBC recycling. From this concept, to reduce melt loss, namely, to gain high recovery rate of metal from UBC scrap is necessary. Both to collect high quality UBC and to determine the conditions of delaquering and remelting are very important. Not only a study of metal-recovery method from the dross formed in the melt furnace while remelting, but also a utilizing study to pass without carrying the remaining ash after the dross treatment to the reclaimed land are required. Judging from the metal balance in view of Mg and Mn content to return aluminum alloy for can in the closed-loop, up to about 75% of Can to Can ratio is acceptable to use properly both 3000 series for body and 5000 series for end. As a future issue, however, the development of aluminum alloy to increase the usage of recycled metal is important. Currently, 5042 and 5021 alloys are beginning to use for end stock. It is ultimately desirable that an uni-alloy such as 5017 alloy is developed. The higher UBC recycling ratio will be, the more the environmental loads will be remarkably reduced as shown in Life Cycle Analysis. It is concluded that aluminum can is the product to be able to enter in the closed-loop system in comparison with other packaging containers.
Aluminum cans have been widely used for content of beer and soft drink. They have many advantages to other cotainers such as steel cans, pet bottles, glass bottles and paper cotainers in these contents. Corrosion resistance of both sides, outer and inner, of the can, is a predominant requirement for the can use, and its mechanism has been developed. Corrosion resistance of inner side mainly depends on storage conditions and ingredients of the contents, for example storage temperature, the concentration of chloride ion and residual oxygen. Two types of corrosion at outer side of the cans are popular. One is stress corrosion cracking of aluminum end. The other is secondary corrosion, caused at outer surface of the can with leaked contents. Recent developments, materials, corrosion evaluation methods for Aluminum cans are described.
TULCTM (Toyo Ultimate Can) is a 2-piece press formed can using thermoplastic film laminated ECCS. It is required for the laminate to have excellent formability and strong adhesive strength to withstand the severe forming of the can body. In this paper, development of ECCS, polyester film and lamination technologies are described. By using the developed material, dry forming 2-piece can manufacturing system was accomplished and the following merits can be obtained; the metal can with high corrosion resistance and excellent flavor retention, and elimination of the can manufacturing energy, elimination of CO2 generation and solid waste generation of the can manufacturing process.
Packaging steel such as Tinplate and TFS or ECCS (Electrolytic chromium/chromium oxide-coated steel) has been growing with its superior performance to fit a can-making process. Since the end of the 20th century the packaging steel is facing a very difficult of time in competition among steel cans, aluminum D&I cans and PET bottles. In order to survive this tough war the packaging steel will has to be innovative with laminated steel to reflect consumer's preference, for example, environmental issues, safety, convenience and cost performance. One of technical key points to put an excellent performance on the packaging steel would be to explore not only amount and composition of coating layer, but a micro-fine structure on finished surface.
Accelerated deterioration tests were carried out to evaluate the anticorrosive properties of alkyd, chlorinated rubber, urethane, and epoxy resin varnish coatings. During the deterioration test, the specimens were exposed to weathering conditions, that is, xenon light irradiation in a Weather-O-Meter. Three different methods were used to evaluate the anticorrosive performance of coatings and the results obtained were compared with each other. The gloss retention, change of chemical structure and impedance of coated specimens were monitored using gloss meter, FT/IR-ATR, and electrochemical impedance spectroscopy, respectively. It was shown that the evaluations of the coatings by three different methods reveal similar results. It was demonstrated that the anticorrosive properties of coatings changed dramatically according to resin. The anticorrosive performances of coatings were found to decrease in the order of urethane>alkyd>epoxy>chlorinated rubber resin coating.
The microstructure of type AZ63 magnesium alloy anode for catholic protection and the dissolution behavior of the anode in tap-water were analyzed with an electron probe micro analyzer, a scanning electron microscope with energy dispersive X-ray spectrometer and a microscope. Crystal grain of this alloy anode was composed of Mg solid solution with very slight content of Al, and the grain boundary of this alloy anode was composed of Al-Mg mixture phase and Al-Zn-Mg mixture phase. When this anode dissolved sacrificially into the electrolyte, Mg dissolved more preferentially than Al and Zn. The local cell was formed within the anode. The grain boundary or impurities acted as cathode of the local cell, and the Mg solid solution as anode. Gray coarse particles fell from the surface of the anode. The cause of this phenomenon was that the dissolution of the anode was not uniform. Those particles contained un-dissolved anode in metallic form.