What Is Soda Blasting?
Soda blasting is a form of abrasive blasting that uses sodium bicarbonate as an abrasive media. The soda is propelled using compressed air or water to blast a surface.
Before we look at what soda blasting is, let’s look at the definition of abrasive blasting.
What is Sand Blasting?
Sandblasting is the common term for abrasive blasting, which is the propulsion of abrasive particles against a surface to remove contaminant or coatings, make a rough surface smooth, or make a smooth surface rough (aka creating an anchor pattern).
The first blasting process was patented in 1870 by Benjamin Chew Tilghman.
The basic components required for abrasive blasting are a pressure vessel, compressed air, abrasive media, and blast nozzle.
Your compressed air is the source of acceleration. In the pressure vessel (aka blast pot or pressure pot), media and compressed air and media are combined, pressurized, and then forced through the blast nozzle. The size and shape of the blast nozzle can change the acceleration or means of propelling blast media at a surface.
Abrasive blasting uses kinetic energy to move the particles of blast media. The compressed air gives energy to the abrasive blast media. The higher the PSI, the more force the media is accelerated with. The higher the air pressure, the quicker the blast media and air wants to escape, meaning more blast efficiency.
The Difference Between Soda Blasting and Regular Sandblasting
Soda blasting gets its name from the type of blast media that it uses: sodium bicarbonate (baking soda). The abrasive media used for soda blasting is not the baking soda that you buy in the grocery store. Companies such as Armex and Natrium manufacture varieties of sodium bicarbonate specifically for soda blasting.
Most formulations of blasting soda have uniform particle sizes between 70 and 270 microns.
Compared to other forms of blast media baking soda is not as abrasive. From a practical standpoint this means that soda will not profile the surface you are blasting.
Soda blasting Is not as aggressive as other forms of abrasive blasting. Sodium bicarbonate is used as an abrasive media in cases where it is important to not leave a surface profile, or damaging the substrate is not an option.
History of Soda Blasting
Soda blasting was first used in the early 1980s in the restoration of the Statue of Liberty. Traditional sand blasting was not viable for several reasons. The interior of the Statue is coated with multiple coats of paint and coal tar, while the exterior is plates of relatively thin copper plates. The interior passageways of the Statue of Liberty are rather narrow, which means ventilation of the dust caused by abrasive blasting would have been problematic.
The solution was to use sodium bicarbonate as an abrasive media. This prevented damage to the thin copper veneer.
Since then, soda blasting has been used for a variety of applications by media blasting companies who converted from traditional abrasive blasting to soda blasting.
Uses for Soda Blasting
There are numerous practical uses for soda blasting. These include:
- Paint removal
- Cleaning in food processing plants
- Stripping and cleaning car frames and parts
- Graffiti removal
- Maritime – cleaning ship hulls
- Cleaning carbon, grease and grime from parts
- Historical restoration
- Cleaning masonry
- Wood restoration, stripping, and cleaning
- Removing street lines from roads
- Fire restoration
- Mold removal and restoration
- Cleaning anilox rolls in printing presses
- Gum removal
- Cleaning drilling heads in the oil & gas industry
- Removing calcium deposits from metal
Soda blasting is also often used for cleaning in power plants, aerospace, electronics, and water treatment centers.
Soda as a Blast Media
Sodium bicarbonate is 2.4 on the Mohs hardness scale, much lower than other blast media such as silicon carbide, aluminum oxide, glass, or even plastic urea. The chemical compound for sodium bicarbonate is NaHCO₃.
Unlike other types of abrasive media, sodium bicarbonate is a single-pass media. It cannot be recycled for additional use. Soda is very friable. This means when it impacts a surface, the particles explode into much smaller particles. What is left afterwards is a fine dust, which is not viable for use for further abrasive blasting.
It is best to use direct pressure at a lower PSI when using soda versus other blast media.
Another thing to note is that soda blasting is not viable for strengthening a surface through peening, as the pressure and media are not meant for this use.
Sodium Bicarbonate is a crystallized particle that is safe for most surfaces. Unlike many media, it does not leave particle residue embedded in the surface profile. Soda is also water-soluble, environmentally-friendly, and non-acidic. It has a pH of 8.
If you are soda blasting near plant life, exercise caution, as the soda bicarbonate can cause discoloration or damage to grass and other flora after exposure.
Practical Abrasive Blasting With Soda
Pressure systems are more efficient than suction systems for soda blasting. Though many sodablasters use portable units, it is also common to soda blast in a contained unit like a blast cabinet or a blast room. If you are using a blast cabinet, consult the manufacturer for guidance on how to set up for soda blasting. Most sandblasting cabinets are set up to recycle media, but soda bicarbonate is pulverized though on the initial pass, and the dust collection needs adjustment compared to regular blast cabinets.
The reason being, most blasting cabinets are set to collect unusable dust from the blasting process, recycling the usable media that remains. With soda blasting, the sodium bicarbonate explodes into dust on impact, so without adjustments, the dust collector will quickly become clogged.
Personal Protective Equipment for Soda Blasting
Sodium bicarbonate is a nuisance dust, so you should use proper protective equipment. This can include outerwear, a face shield, a proper dust filtration mask, safety glasses, ear protection, and sandblasting gloves.
Costs of Soda Blasting
The costs of soda blasting are slightly higher than that of traditional sand blasting. These are for the media, machinery, and labor.
Other abrasive blast media, like glass beads, steel shot, or garnet, have a stronger molecular structure, and can usually be recycled. Because of the high friability of blasting soda, (the media disintegrates after the first use), the ongoing cost of blast media may be higher than with traditional sand blasting.