Chromate-free is defined as "Hot-dip zinc-coated steel sheets and coils," meaning that the chemical conversion coating does not contain hexavalent chromium  (Japanese Industrial Standard (JIS) G3302)".

"Chromate Treatment," on the other hand, is a chemical conversion process performed using a solution containing hexavalent chromic acid. For metals, the method forms a protective oxide film, thereby significantly enhancing corrosion resistance. Conversely, its application to plastics induces the formation of polar groups on the surface, significantly improving adhesion and receptivity to paints and adhesives.

Hexavalent chromium was widely adopted due to its low cost and high corrosion resistance. However, its compounds are highly toxic. Due to serious concerns about direct contact, indirect harm to the human body through environmental issues such as soil contamination, chromate treatment is being progressively phased out.