Hot dip galvanization is a widely used method for protecting steel from
corrosion. In the hot dip galvanization method, the steel material to be
coated is dipped in a molten metal bath of zinc or of an alloy of zinc containing
alloying elements such as Al, Mg, Ni Co and Mg. Hot dipping can also be followed
by heat treatment (annealing) resulting in a Zn-Fe (galvanneal) coating over
the steel. The zinc/zinc-based alloy coatings act as sacrificial anode thereby
protecting the underlying steel from corrosion.
The invention relates to an improved protective coating composition for
hot dip galvanization of steel. An improved protective coating composition
hot dip galvanization of steel, the composition comprising zinc and strontium
along with other alloying elements wherein the strontium is present in
at least 0.01 to 0.1 % by weight of the composition.
The coatings using strontium
containing improves the adhesion strength, delamination resistance as well
as corrosion resistance as compared to
the coatings using
strontium free Zn composition or using the commercial HDG composition.
The adhesion strength is improved by around 33%, delamination resistance
75% and of corrosion resistance by around 4 times. The improved properties
of the coatings ensure superior protection of steel.
Indian patent application no. 247/MUM/2008 Indian patent grant no. 256103
Inventors: V S Raja and S T Vagge