PPGI is pre-painted galvanised iron, also known as pre-coated steel, coil coated steel, color coated steel etc., typically with a hot dip zinc coated steel substrate.
The term is an extension of GI which is a traditional abbreviation for Galvanized Iron. Today the term GI typically refers to essentially pure zinc (>99%) continuously hot dip coated steel, as opposed to batch dip processes. PPGI refers to factory pre-painted zinc coated steel, where the steel is painted before forming, as opposed to post painting which occurs after forming. The steel thus produced in this process is a prepainted, prefinished and ready for further processing into finished products or components to use material.
The coil coating process may be used for other substrates such as aluminium or stainless steel or alloy coated steel other than "pure" zinc coated steel. However, only "pure" zinc coated steel is typically referred to as PPGI. For example, PPGL may be used for pre-painted 55%Al/Zn alloy-coated steel (pre-painted GALVALUME(r) steel*).