Since the Chinese calendar is a lunisolar calendar, the last day of a year is also called lunar New Year's Eve (Traditional Chinese: å¤§å¹´å¤, Pinyin: dÃ niÃ¡nyÃ¨, translated: old, large, huge, major, important year's night).
While aluminium doesn't rust, it often becomes dull from corrosion, and is often encrusted with brake dust, calcium, lime, tarnish, grease, oil and hard water stains. Simply washing it off will not work, you need something stronger and more effective to do the job.
The only exception to this alloy numbering system is with the 1xxx series aluminum alloys (pure aluminums) in which case, the last 2 digits provide the minimum aluminum percentage above 99%, i.e., Alloy 1350 (99.50% minimum aluminum).