WET BEAD BLASTING
Alternatively known as vapour blasting or aqua-blasting, this has some distinct advantages over dry bead blasting.
It is a less costly process because it requires lower air pressure and fewer CFM as the bead/water slurry is pumped up to the blast gun. Dry blasting however, requires higher pressure and CFM to produce the vacuum developed in the blast gun’s venturi to draw the media up to the gun. Lower pressure means reduced electricity consumption, less machine wear and less media breakage.
Because the media is suspended in water no dust is produced so there is no need for vacuum systems and filters. Another distinct advantage is that parts will not overheat because the water cools the workpiece, meaning thinner sections may be blasted without distortion.
A further advantage is that the slurry jet obviates the need to earth the component to eliminate static shock.
Finally, wet bead blasting produces a better finish and the process can be controlled to produce different finishes.
DRY ABRASIVE BLASTING
Abrasive blasting is used to clean surfaces of contaminants (eg corrosion or paint) and etch them to aid adhesion of a subsequent layer such as paint or powder coating.
There are many types of abrasive media such as crushed glass, garnet, aluminium oxide and silicon carbon with differing properties of hardness, toughness, aggression etc. We have settled on using medium grade crushed glass for removing paint from steel prior to painting or powder coating where the etched surface encourages adhesion.
Where soft metals have been heavily corroded and caked in burnt-on oil, a pre-blast with fine crushed glass at low pressure removes all the contamination leaving a finely honed or etched finish which can then be peened with glass beads to a lustrous finish.
Crushed glass has one drawback: its useful life is limited as the sharp corners of the glass particles get worn down and the particles themselves fracture so it becomes less effective. Also, we regularly change our glass media because free iron particle contamination from blasting ferrous metals causes corrosion of stainless steel.