Abstract: A method of producing a steel sheet coated with a fluororesin film by heat-fusing the fluororesin film onto a surface of the steel sheet, comprising heating the surface of the steel sheet to a temperature higher by 30-120 degrees C. than a melting point of the fluororesin of the fluororesin film, and contact bonding the fluororesin film onto the steel sheet surface between a pair of rolls, while a surface of a roll facing the fluororesin film, in the pair of rolls, is heated to a temperature lower by 100-210 degrees C. than the melting point of the fluororesin of the fluororesin film.

Abstract: A process for improving the rust and corrosion resistance of thinly coated tinplate is disclosed, wherein a steel sheet coated with 0.02-0.2 g/m.sup.2 of nickel prior to annealing is coated with 0.05-1.5 g/m.sup.2 of tin, subsequently being trated with 0.3-10 C/dm.sup.2 of chromate and then subjected to a treatment of melting tin (reflow). A layer of alloy thus formed is highly rust resistant and structurally different from any of those formed on thinly coated tinplate according to the prior art, so that highly rust resistant tinplate sheets for use in the manufacture of welded cans can be obtained.