|
|
In the arc spraying process an electrically conductive
material is changed from the solid state into the liquid state by means of
an electric discharge process and subsequently applied to a substrate
surface. The process is based on the principle that two electrically
conductive wire spray materials (e.g. zinc) are brought together at a
constant feed rate. The angle at which the wires are brought together may
range from 30 to 60 degrees.
Between the two wires an electric arc is initiated which serves as energy
source for melting the spray material. In the arc, a temperature of more
than 4000 °C is attained. High current densities of over 100 A/mm2
immediately melt the wire ends. The molten material is atomized and
accelerated by a gas stream (compressed air or an industrial gas). Finally,
it is deposited on the surface of the component to be coated. When striking
the surface to be coated the droplets solidify and form a firmly adhering
coating.
In spray coating of concrete, the concrete surface is first to be cleaned
and roughened to achieve a satisfactory adhesive
strength. Zinc sprayed coating is then applied in several layers.
Zinc sprayed coating is
connected via electric contacts with the steel reinforcement.
The coating thickness of the zinc anode influences the service life of the
corrosion protection system and is usually in the range of 300 to 500 µm.
The adhesive strength is in the range of 1.5 to 3.5 MPa. Special measuring
methods allow determination of the mechanical stability of the zinc coating
on the concrete.
|
|
