Abrasive blasting is generally used to prepare materials for their subsequent finishes.
Steam and Sand Porirua Ltd has the largest blast booth in the country for its steel grit operation, the grit is filtered, cleaned, and reused a number of times.
Existing surfaces are removed (mill scale, rust, paint, etc) and a surface profile is formed to suit the finish to be applied by blasting with high pressure air and a blasting medium. It is very important that this surface profile is correct to provide the necessary anchor to achieve the durability of the subsequent finishes.
The most used blast mediums are garnet, a naturally occurring completely inert material that is imported for the purpose, steel shot in different configurations (size, crushed as grit, etc) and crushed glass. Garnet and glass can generally be used in an open environment, steel grit is used in a closed environment, generally a blast booth.
Sand blasting is a process of the past - sand is no longer used, it contains silica and is a danger to the health and to the environment.
There are four main types of blasting media that can be used.
Garnet is a blasting media free from silica and iron particles, which can be sourced from either India or Australia.
Garnet would generally be used for mobile or onsite applications as it has lower dust levels than iron sand. Garnet is the main blasting media we use for onsite applications.
Grit is finely crushed ball bearings which gives the steel the blast profile needed for paint to adhere to the surface. Grit can not be used on anything that has a magnetic force such as alternators etc.
Glass Bead is used when a fine surface finish is required - such as restoration of cars or sculptures.
Shot is a ball bearing like blasting media, very small in size - .04mm to 1.4mm. It is very popular with recycling units as it can be reused 40 to 50 times. As with grit, shot can not be used with anything that has a magnetic force either.
Iron sand is a traditional blasting media normally found on beaches around New Zealand, but due to recent studies has been found to be harmful to operators of blasting equipment. We no longer use this media because of this reason.