Soda Blasting with a Dana-Ridge Wetblast machine Q & A

At Dana-Ridge we often get enquiries about soda blasting and asked if it’s possible in our wetblast machines. Sodium bicarbonate (NaHCO₃) is a soft, granular, friable, sharp, benign blast media.

NOTE: Prior to using sodium bicarbonate on your part always do a test patch on a similar material to determine its suitability

Can you use soda in a Dana-Ridge wetblast unit?

Yes. Not only is it possible but it’s actually better than a dry setup. It lasts longer and you don’t have to worry about it getting wet as you do with a dry unit. Having it contained in a cabinet means it eliminates the clean-up time associated with an open system.

When would you use it?

It is sometimes used in the automotive arena such as blasting oil galleries, carburetors, diesel pumps, injectors It is used in a variety of applications for the removal of coatings such as soil, paint, grease, oil, carbon, and light surface rust from just about all substrates. It will not remove heavy rust however.

Why would you use it?

Anywhere where you have an assembled part and you either want a matte finish or can’t easily clean out remnant media.

What kind of finish will it give?

Contrary to a widely held belief, soda will not give a nice bright surface. It will give a matte finish.

Advantages and Disadvantages of Soda Blasting

Advantages

  • Friable – soft angular grains readily fracture into smaller particles intensifying the cleaning action while softening the impact on substrates.
  • Water soluble – eliminates media residue concerns and simplifies clean-up
  • Safe to use on virtually any substrate, including delicate surfaces, rotating equipment and moving parts but still able to remove coatings.
  • Able to be washed out of internals easily meaning no damage to moving parts.
  • Contains no free silica
  • Contains no solvents or caustic chemicals
  • Environmentally friendly
  • Non-toxic and non-hazardous as defined by the EPA and OSHA – with a pH level of 8.2
  • The angular shape of the sodium crystal has a scouring effect on the substrate that will virtually clean any coating from the surface

Disadvantages

  • Unable to remove heavy rust and scale
  • Gives a matte finish (may be an advantage if it is the desired effect)
  • Shorter media life
  • Slightly alkaline, causing crystals to form on blasted parts (this can be neutralised in a slightly acidic solution of vinegar and water after blasting)
  • In a dry sandblasting cabinet, water is an issue (not in our wet system though)

Are there different sizes?

There are several grades of granular sodium bicarbonate available from fine (< 63 microns) to ultra-coarse (< 270 micron). For quick cleaning results it is recommended to use the ultra-coarse grade material.

Do I have to use it as a “soda only” machine?

You can change the media out to whatever you want. If you change from a media such as glass or oxide or garnet and the like, you would need to make sure you clean out any remaining media from behind curtains and split the pump to clean out any particles. If you’re using soda with the intention of avoiding damage inside assembled parts then it’s worth taking the time to clean it out well.

Is there an alternative?

Glass bead is more commonly used than soda for most applications. It gives a bright finish and can remove rust. If you can disassemble the part, then you can avoid getting bead where you don’t want. There are a couple of other tricks to avoid getting media where you don’t want it

  1. Cover any areas you don’t want blasted with a cloth impregnated tape. It’s readily available from places like Bunnings and Supercheap Auto. The tape resists the blast for a time as the media bounces off.
  2. Putting a blob of silicone in any holes and letting it harden, forming a plug. The blast stream will bounce off the silicone in then you can just pry it out afterwards.

How to I set my machine up for soda blasting?

  1. Make sure you have a clean machine as described earlier.
  2. Using sodium bicarbonate in the wetblast cabinets requires the sump water to be first super-saturated with the media. Any additional sodium bicarbonate added after that gives you the concentration required for blasting.
  3. Once you have completed blasting your components it is recommended to dip the components in either fresh water or a mild acid solution to dissolve and neutralise residue soda and ensure there is no sodium crystal growth on the blasted part.

(A 10-15% vinegar, 85-90% water solution is all that is required)

Charging the machine for use

How much media do I need to super-saturate the sump?

The amount required is dependent on the sump water temperature. The table at the very bottom of the page will indicate what percentage to add. For example, if a comet machine has a 28L sump and the water temp. is 20 then according to the chart you would add 9.6% of soda which is 2.7kg of soda.

We’re not done yet though. Now we need to add some more (see the following) …

How much extra to add after that?

Now that we have super-saturated the water as per the above step, we need to get our blast level up to around 25-30% which is the optimal blasting range. The following table will show the amount to add for our 3 most popular machines…

  

Mercury model

(26 Litre sump)

Comet model

(28 Litre sump)

Mars model

(125 Litre sump)

 
% Conc.Approx. kg Sodium Bicarbonate
8%2.082.2410
10%2.62.812.5
12%3.123.3615
14%3.643.9217.5
16%4.164.4820
18%4.685.0422.5
20%5.25.625
22%5.726.1627.5

Optimal

range

24%6.246.7230
26%6.767.2832.5
28%7.287.8435
30%7.88.437.5
 32%8.328.9640
34%8.849.5242.5
36%9.3610.0845
38%9.8810.6447.5
40%10.411.250

Do I have to top up?

When you are blasting and adding fresh water with the windscreen spray wash you are further dissolving your blast media. Whilst the loss of blast media with this is small (nominally 0.2 kg per blasting hour) the rate at which the sodium bicarbonate blast media is dissolved is dependent upon how much fresh water is added into the machine so keep the windscreen wash rate to a minimum.

As for the rate of consumption while blasting it can depend on variables such as the air pressure used. When it has impacted on the part enough times to the point of no longer doing useful work it will tend to dribble out the overflow.

It is recommended you use the media concentration jar to check regularly. Soon, you will be guided by experience and will have less use for the measuring jar. Too much media causes blockages, too little decreases productivity.

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