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Best blasting methods for various soils and surfaces October 7, 2020

 

Has trying to choose which type of blasting you need given you a headache?

Fair enough.

With the wide range of abrasive and non-abrasive blasting methods available today, it can be overwhelming trying to figure out what will work best for your situation.

 

Presco Environmental technician, Te Kepa, steam cleaning grease off a kitchen extraction cowling.
Presco Environmental technician, Te Kepa, hot water pressure washing grease off a kitchen extraction cowling.

 

This article will try to help by:

  1. Summarising the 9 most common blasting media options
  2. Listing what works best on different soils
  3. Listing what works best on different surfaces
  4. A bonus chart to tie all your options together

 

1. Common blasting media options

 

Non-Abrasive blasting

Water Blasting

Water blasting, also known as pressure washing, is the lowest cost and most readily available option.  It can perform a wide range of cleaning tasks.

In some situations, however, pressurised water can cause maintenance issues.  The high pressure  pressure (normally 3,000+ PSI compared to 150-300 PSI for air blasting) can force water into places it should not be.

This high pressure can also spread dirty water and soil around the work area.

 

Presco Environmental technician pressure washing silos at a dairy factory
Presco Environmental technician pressure washing silos at a dairy factory

 

Dry Ice Blasting

Dry ice blasting uses frozen carbon dioxide (CO2) gas pellets as the blast media.  It is a very versatile and safe option.

The CO2 pellet sublimates (turns back into gas and disappears), leaving no water or secondary waste to clean up.  This is excellent for cleaning without making a mess.

Dry ice blasting is totally non-abrasive and can clean over glass, rubber, sensitive electronic components and seals.

Learn more about dry ice blasting here.

 

Presco Environmental technician, Rob, dry ice blasting paint off scaffolding
Presco Environmental technician, Rob, dry ice blasting paint off scaffolding

 

Abrasive blasting

Sand/garnet

Sharp edges and uniform media size for surface profiling, make sand blasting fast.  This made it the go-to media for heavy blasting up until recently. 

Health issues associated with free silica in the sand blasting process and the environmental clean-up issues associated with its use has caused most to look for alternative, safer media.

 

Aluminium Oxide

Aluminium Oxide is one of the harder abrasive media options to replace sand/garnet.

✔ It is fast at profiling and paint removal.
✔ Lightweight so okay for thin materials. 
❌ Can be too harsh for some surfaces and is harsh on the blasting equipment.

 

Glass Bead

Round glass beads do not contain silica like sand blasting. The beads are easier to recover and will clean effectively for more cycles than sand (often 20-30 cycles).

✔Great for blast cabinets.
✔Metal cleaning
✔ surface finishing (attractive metal finish)
✔ deburring and peening.

 

Plastic bead

Plastic beads do not contain silica and create low dust levels.  They are good for more delicate cleaning. Plastic bead blasting is slower than garnet/sand or aluminium oxide, but the beads are easier to recover  and will clean effectively for more cycles than sand (often 20-30 cycles).

✔Great for blast cabinets.

 

Walnut shell

Walnut shell is a relatively soft nutshell abrasive for removal of top coating without etching, scratching, or marring surfaces. The pellets possess high strength and resist break down, but are non-abrasive in character.

Walnut shell is most widely used when very close tolerances must be maintained.

✔ excellent reuse
✔ low dust
✔ usable in all types of blasting equipment

 

Soda blasting

Baking soda (sodium bicarbonate, NaHCO3) is a relatively soft, single use, water soluble blast media used for cleaning and stripping surface materials or contaminants without damaging the base or substrate material.

 

Hybrid options

There are also hybrid blasting media combinations available now, such as:

  • air/water/garnet
  • water/garnet
  • dry ice/garnet
  • water and soda

These all aim to find a middle ground between the respective media benefits and their undesirable health & safety and environmental side-effects. This is smart technology and options should be investigated for any abrasive blasting job.

 

2. The best blast media option for each soil type

 

Food product: What is the best blasting option for removing fats and proteins?

Water, dry ice, and soda blasting are all used.

Pressurised water is the lowest cost method but is quite messy due to its higher pressure compared to both other methods.

Soda blasting is very effective but also involves quite a lot of clean up.

Dry ice blasting cleans as effectively as the other two and has zero secondary waste to clean up, but is the costliest blasting media.

 

Food product: What is the best blasting method for removing dry powder and cereal?

Water, dry ice, and soda blasting are all used, except in a ‘dry’ plant where moisture needs to be avoided at all costs.  Here dry ice is the preferred option.

If moisture is allowed, the options are the same as ‘fats and proteins’ above.

 

Dry Ice Blasting removing milk powder from pipes
L: milk powder built up on pipes;
R: the same pipe after the powder has been removed by dry ice blasting

 

What is the best blasting method for removing ink?

Dry soda blasting and dry ice blasting are used to clean printer’s ink off a press without damaging the components of the press.

Soda blasting is mildly abrasive and requires flushing the blast media out of all areas afterwards.

Dry ice blasting is the preferred option here; it is completely non-abrasive and leaves no blast media to clean up afterwards.

 

Dry ice blasting removing ink off a printer in a milk packaging facility

 

What is the best blasting method for removing dust?

Water and dry ice are the two common methods for removing dust and dirt build up without damaging the surface being cleaned.

Pressurised water is the lowest cost option if water can be used (not around electric or electronic components or in a dry plant.)

Dry ice blasting is very effective in dust removal without damaging the substrate.

When dry ice blasting in explosive dust environments, caution must be taken to earth out equipment and have insulated lances, due to the static energy created.

 

What is the best blasting method for removing heavy rust scale?

Sand and aluminium oxide remove rust scale well and fast, but have health and environmental risks to manage.

If the scale is not too excessive, soda blasting does a good job and has much less associated risk.

All methods require clean up and disposal of the blast media.

 

What is the best blasting method for removing rust stain?

Soda blasting is the preferred method for removing rust stain from steel unless you need to avoid water or cleaning up the blast media. In that case, Dry Ice blasting is usually able to remove rust staining from steel or painted surfaces without damage and with zero waste to clean up.

 

What is the best blasting method for removing glue?

Dry Ice Blasting is a most effective way of removing glue build-up as the super cold (-79 °C) frozen CO2 makes the soft glue more brittle, allowing the impact of the pellet to shatter and dislodge the glue.

 

What is the best blasting method for removing bitumen and tar?

Dry ice blasting is a most effective way of removing bitumen and tar build-up as the super cold (-79 °C) frozen CO2 makes the soft tar more brittle, allowing the impact of the pellet to shatter and dislodge the bitumen.

 

What is the best blasting method for removing mould and bacteria?

Dry ice is the preferred blasting method for removing mould as the super cold (-79 °C) frozen CO2 has a sanitising effect and removes the mould spores.

 

What is the best blasting method for removing soot and carbon deposits?

Dry ice blasting removes soot very well (particularly after a fire.)

Due to being waterless, the soot is not smeared or transported to other areas during cleaning; just frozen and knocked off the surface to fall to the ground (use drop sheets to capture the soot and protect floor coverings inside dwellings).

Dry ice blasting also removes carbon build-ups in ovens quickly, without creating any secondary waste to clean up.

 

Dry Ice Blasting to clean building exterior
Dry ice blasting removing smoke damage from a house exterior

 

What is the best blasting method for removing paint?

For fast paint removal and ‘keying’ of the metal surface in preparation for repainting, abrasive blasting (sand/garnet/aliminium oxide) is the most effective. It will however damage any rubber, glass, plastic or soft metals so will require more disassembly and more masking up.

The softer bead blasting (glass, plastic, walnut) and soda blasting will remove paint without damaging the substrate and is easier on the more sensitive components. These options are slower than abrasive blasting but less destructive.

Dry ice blasting is the gentlest of all blasting methods and can remove paint if the ice feed and air pressure are maximised. This method is best for sensitive or soft substrates and areas where you cannot have secondary waste (i.e. line marking removal inside a food production hall,) but is relatively slow.

 

Presco Environmental technician, Jeremy, dry ice blasting paint from scaffolding
Presco Environmental technician, Jeremy, dry ice blasting paint from scaffolding

 

What is the best blasting method for removing concrete splatter?

If the concrete splatter is light and fresh, standard pressure washing can usually remove it without damaging the surface.

Cured concrete splatter can be removed with dry ice or soda blasting without damage.

If the concrete has been allowed to build up over time, it will take abrasive blasting to remove it.  In most cases, this will take the substrate back to bare metal.

 

3.   The best blast media option for each surface

 

What is the best blasting method for food production equipment?

Water is the cheapest method of cleaning in a food production environment.

However, water blasting can push dirty water into crevices and spread contamination around despite how careful the cleaning operator is being.

Dry ice blasting creates no secondary waste, so is the safest blasting method in a food production environment but costs significantly more than water blasting.

 

What is the best blasting method for electrical components?

Dry ice blasting is really the only blasting method suitable for electrical componentry and, even then, only with the correct equipment and an experience operator.

In the right hands, dry ice blasting can clean circuit boards and live electrical switch gear.

 

What is the best blasting method for seals and bearings?

Dry ice blasting is the preferred choice for cleaning around seals and open bearings.  This is because it is gentle enough, completely non-abrasive, and leaves zero media residue behind.

 

What is the best blasting method for ovens?

If the oven can be stripped down and blasted with high pressure hot water, this would be the cheapest option.

To clean in situ, especially between shifts while still hot, dry ice blasting is the answer.  It creates zero secondary waste to clean up and the thermal shock of cleaning hot plant with super cold (-79°C) dry ice shrinks the baked on carbon deposits shrink.  They immediately become brittle, which makes them very easy to dislodge.

 

What is the best blasting method for engine degreasing?

Soda blasting is very good for engine degreasing and also brightens alloy steel nicely.

Dry ice blasting is also very good on solid grease building up and is less abrasive, which is great for seals and bearings but means it doesn’t have the same ‘brightening’ effect as soda.

 

What is the best blasting method for conveyors and chains?

If you can manage dirty water in the area, then pressure washing would be the cheapest option.

For cleaning in situ, dry ice blasting has two advantages:

  • a very effective clean
  • zero secondary waste to clean up.

 

Presco Environmental technician, Henry, dry ice blasting UV coating off a driver chain.

 

What is the best blasting method for structural steel?

Abrasive blasting (sand/garnet/aluminium oxide) is the best method of preparing structural steel. Abrasives ‘key’ the surface, creating a profile which results in a better bond of any surface coating applied.

 

What is the best blasting method for moulded metal components?

Lightly abrasive blasting media, such as glass and plastic beads, are all suitable for de-flashing and de-burring moulded metal components.

Usually this would be done is a blast cabinet where the blast media can be captured and reused multiple times.

 

What is the best blasting method for hot surfaces (steam/hot water pipes)?

Dry ice blasting is an excellent method for removing soil from hot surfaces. As mentioned in ‘Ovens’ the thermal shock of cleaning hot surfaces with super cold (-79 °C) dry ice makes the baked-on soil deposits shrink and become brittle, which makes them very easy to dislodge.

 

What is the best blasting method for cold surfaces (chiller/freezer walls)?

Soil on cold surfaces, especially in freezers, is best dislodged with even colder blast media.

Water cannot be used in these situations as it freezes.

Collecting up other forms of dry blast media is very difficult in sub-zero conditions.

Dry ice pellets are -79°C.   Dry ice blasting creates zero secondary waste and is great for de-dusting or de-icing freezers.

 

4. Best blast media option for common cleaning situations:

 

Table showing best blast media for different tasks

NB: Poor refers to a media that is not well matched to the task.  It may either damage the substrate being cleaned or be ineffective on the soil type.

 

5. Summary

There is no ‘silver-bullet’ blast media option. The ‘best’ blast media option is different for each surface and soil type.

It is important to establish the surface type being cleaned; the soil type to be removed; and the desired outcome before researching blast media options.

Once you have that, use the information in this article to select the one or two best media options and search online for a specialist contractor in your area that provides that service. Each blasting method requires operator skill and a lot of experience to deliver a great result.  Check the contractor’s previous jobs and customer testimonials to be certain they can deliver the outcome you need.

Be careful of contractors that say they can do everything! It is usually better to use a specialist or expert contractor.

All the best 🙂


 

This article was written by Matthew Prestidge of Presco Environmental and based on options available in New Zealand at time of writing.

Have further questions? (Or would you like to give feedback on this article?) Feel free to message the author at matthew@presco.co.nz.

 

Matthew Prestidge, General Manager

About the Author

Matthew Prestidge is our General Manager and Senior Industrial Hygiene and Indoor Air Quality advisor.

Having spent the last 15 years creating more sustainable environments on industrial sites, Matthew has seen the good, the bad and the ugly and knows what is required to “clean up”.   

Would you like to discuss solutions to industrial cleaning issues?  
Matthew offers a free consultation and easy-to-implement advice on Industrial Hygiene and Indoor Air Quality for anyone in the New Zealand Food and Beverage industry. Contact him at matthew@presco.co.nz

 

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