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The
process
of thermal
diffusion zinc coating is a new environmentally friendly process. The process
is designed for coating of small and medium-sized items, including threaded,
made of steel and cast iron, requiring the coating thickness above 20 micron,
and operating in the open air, in the industrial and sea atmosphere.
The
thermal diffusion zinc coating has a number of essential advantages:
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A
high corrosive resistance;
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Coating
follows exactly to item's shape with all its particular details (threads,
marks, and other delicate relief of item's surface);
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This
technology excels other methods of zinc coating in hardness and resistance
to an abrasive wear (till 1500 hours in salt spray chamber);
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The
temperature of saturation is not particularly high; therefore, the coating
can be applied on spring-type and other preliminary heat-treated items;
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The
process allows coating of items produced by a powder technology,
iron-based sintered parts (without previous impregnation), as well as
welded and pre-assembled movable items;
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The
technology allows to coat items with a minimal pretreatment of surface
before coating. Spots of rust, rests of grease, and oiling cooling agent
on the surface of details do not prevent a homogenius coating;
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The
process does not cause to a liquid and solid waste, which requires further
neutralization or burial;
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The
thickness of coating varies within 15 to 80 micron.
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The
structure of upper layer of metal and
defensive thermal diffusion zinc coating
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The coating is variable structure of zinc-iron,
generally FeZn7.
The density of this phase is 7,2 cm3, micro hardness is app.
4500 MPa.
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1. Steel base
2. Solid
solution
Zn in Fe
3.
Fe11Zn40
zinc
rich layer
4.
FeZn7
5.
FeZn7 + Zn
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Thermal
diffusion galvanizing process
The
process is based on the heating of parts, together with special zinc
powder, in a drum or container in a furnace maintained at 360-470oC.
This process results in a diffusion of the Zinc powder to the outer
layer of the steel, creating a protective, corrosion-resistant surface.
Results of 1500
hours in salt spray chamber
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