C-6, Aluminum and Its Alloys (Third Edition, October 2015), is a technical report describing the properties that make aluminum and its alloys the material of choice in packaging, architectural, transportation, chemical, electrical and general engineering applications. First presented at the Annual Liberty Bell Corrosion Course and revised for the 2015 edition by J. Gilbert Kaufman, the report explains the designation system by which alloys are classified and then discusses manufacturability, recyclability and corrosion resistance, the characteristics responsible for aluminum's widespread use, second only to steel as a structural material. References are provided for readers who need more detail. Written as an introduction rather than a specification, the report is used in educational courses and by engineers who need a concise, authoritative overview of aluminum metallurgy.