PURPOSE: To upgrade adhesive power of fluoroplastic by coating the fluoroplastic on an Al sheet, preliminarily sintering the coating to thermally decompose the fluoroplastic and to fluorinate the surface of the Al sheet, then freshly coating the fluoroplastic on the surface and sintering the same.

CONSTITUTION: The fluoroplastic is coated on the Al sheet and is preliminarily sintered for a short period of about one minute at about 400°C to thermally decompose the above-mentioned fluoroplastic and to fluorinate the surface of the above-mentioned Al sheet. The fluoroplastic is then freshly coated on the surface and is sintered for about one minute at about 390°C to form the fluoroplastic coating layer. As a result, the fluoroplastic coating layer which has the intrinsic characteristics of the fluoroplastic coating layer and adheres strongly to Al sheet is easily formed.