The present invention relates to a
metal surface treatment agent, a surface treated steel and a surface treatment method thereof, and a coated steel and a making method thereof. The chromate-free
metal surface treatment agent is most suitable for being used as a
metal coated steel, as the pre-
processing of the coatings, such as the paint, etc., and can provide the excellent processability,
adaptation and
corrosion resistance. The metal surface treatment agent takes the
organosilicon compounds represented by the general formula (1) as the necessary components, wherein R is hydrolytic perssad, R' is
alkyl group having 1-4 carbon atoms, A is a linear chain or branched chain alkylene having 1-8 carbon atoms, X is one of the
oxygen atom, the sulphur atom and the
nitrogen-atom, R1 and R2 independently and separately represent the
hydrogen atom, the
alkyl group having 1-20 carbon atoms, the fluoroalkyl having 1-20 carbon atoms,
aryl having 6-10 carbon atoms and alkenyl having 2-10 carbon atoms, or the
substituent group represented by the general formula (2), m is an integer of 1-3. In the general formula (2), R' is the
alkyl group having 1-4 carbon atoms, B is a linear chain or branched chain alkylene having 1-8 carbon atoms, and m is an integer of 1-3.