Silica sand, flint, and other Silica-Bearing Materials
Silica sand is a very good abrasive. It is hard, gives a superb finish to almost any substrate, is available almost everywhere in the world, and is generally the lowest cost abrasive.
Drawbacks are that it is not always available in large particle sizes; it can be recycled only a few times; and it poses significant health risks for workers.
Silicosis, a chronic lung disease marked by diffuse fibrosis (scarring) of lung tissue, is caused by breathing silica dust, which is created when silica sand abrasive breaks down upon impact. Exposure to very high concentrates of silica dust can cause acute silicosis, resulting in rapidly progressive breathing problems and even death within a few months of onset. More common is progressive silicosis, usually from exposure over a long period, which may develop into lung cancer. The effect of silicosis continues to develop after exposure has stopped, and it is irreversible.
There is a misconception (at least in the UK) that blasting with wet sand can stop the effect of silicosis. However, there is evidence that silica sand suspended as a hydrosol (i.e in water) can penetrate the respiratory track easier then an aerosol (i.e. in air). So although blasting with wet sand will initially keep the dust down, it will not repress it to the maximum exposure limit of 0.3 mg/m³ expressed as an 8-hour time-weighted average.
The UK Health and Safety Executive, which has established these exposure limits, has determined that even general cleaning after blasting by sweeping dry silica sand will produce a maximum exposure level of twice the legal limit and that internal blasting of fresh water tanks on a ship with silica sand produced potential exposures of almost 2,000 mg/m³ of respirable dust (more that 6,000 times the permitted limit).
- Cast Ferrous Abrasives
- Mechanically Produced Ferrous Abrasives
- Natural Asbrasive