HYDRO BLASTING MEDIA
Hydro blasting,
water jetting or water
blasting are terms commonly used
when describing water as the tool to do surface
preparation. The use of water is a technique for
cleaning surfaces, which relies solely on the
energy and force of water striking a surface to
acheive its cleaning effect. In principel
abrasive is not used in waterblasting
equipments, hence, the problems caused by
dust pollution and by the disposal of spent
abrasives are eliminated.
SURFACE CONDITION AFTER HYDROBLASTING
Flash rust :
When large areas are
hydroblasted, flash rusting which
deminish the original surface standard may
occur, before painting can be carried out. The
degree of flash rusting depends on many factors,
such as humidity level, temperature and the
length of time the surface is exposed.
Degrees of flash
rust :
-
Light flash
rust : small quantities of
light tan-brown rust will partially
discolour the original steel surface. The
discolouration may be evenly distributed, or
in patches, but it will not be heavy enough
to mark an object brushed against the areas.
Temperature rise
:
The use of
hydroblasting equipments will cause
the temperature of the steel to rise. The
increase of temperature of the steel surface can
be substantial, depending on the pressure of the
equipment used and will help waterblasted
surfaces to dry off faster, hence reducing the
degree of flash rusting.
Removal of foreign
elements :
The use of water has
the advantage of removing oil and grease from
the surface along with salt deposits. This is a
major plus point of hydroblasting. The
grey, brown to black discoloration of corroded
and pitted steel after waterblasting
cannot be removed by further blasting.
Studies shows that this thin film consists of
mainly ferric oxide, which is an inert material.
As it is tightly adherent, it does not present a
serious contamination problem.
SURFACE PROFILE
Hydroblasting
will not produce a surface profile as such.
Weakend steel might erode, resulting in metal
loss, but the surface profile exposed after
blasting will have been produced by earlier
surface preparation or corrosion.
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