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Blasting Garnet Abrasive – what the corrosion industry is switching to

Over the past 20 years, many blast yards worldwide have changed from Slag blasting products to using Blast-One Australian Garnet for abrasive blasting. The reason for this change is due to surface preparation concerns when using slag and also the cost effectiveness of using Blast-One Garnet.

Many contractors have changed from Slag to Blast-One Australian Garnet abrasive, and are now beating their competition hands-down on many projects.

They are boasting:

  • Higher Degree of Surface Cleanliness
  • Very low dust
  • Much more environmentally friendly
  • Cleaner work environment for workers
  • Higher Production Rates
  • Reduce Abrasive Consumption
  • Reduction in Abrasive waste
  • Lower cost per square foot blasted
  • No toxic waste or heavy metals in Australian Garnet as there is in slag

The True Cost of Abrasive Blasting

What I would briefly like to cover is the economics of Blast-One Australian Garnet versus Slag.

Most Blasters readily agree that garnet is the better abrasive all round. “We don’t have to fill the blast Machine as often; it cleans faster, has hardly any dust and gives a much cleaner job all around”. But often we hear contractors say:

It’s just too expensive to use.

This is the perception of course, because garnet is up to 6 times the price of Slag. In fact, the abrasive cost has very little relationship with the finished cost of the project. Unfortunately, abrasive cost alone assumes all abrasives perform the same.

The following diagram illustrates how spending more on a high performance Blast-One Garnet Abrasive means you end up spending less on all the other costs in a project, ultimately providing a lower overall project cost.

Expense table Sla Vs Garnet

The US Navy developed an accurate costing formula which is based on the fact that the true cost of any blasting operation is the finished cost per square foot. This allows them to accurately cost projects and compare abrasive performances at any of their Naval Dockyards.


(Based on US Navy Cost Formula)

True cost per square foot = A (B+C) + D + E

A = Abrasive consumed per nozzle per hour (in pounds)

B = Abrasive cost delivered per pound

C = Clean up and disposal costs per pound

D = Labour cost per nozzle per hour

E = Equipment running cost per nozzle per hour

X = Square feet blast cleaned per nozzle per hour

To assist you to calculate your actual blasting costs, we have developed a tool to assist you calculate your true cost of blasting – the True Cost Calculator.

But don’t try Garnet out alone!

Before we go any further, it is important to understand that you won’t make more profits by just ‘using’ Garnet! As in if you read this web page, and you would like to try using Australian GMA Garnet, if you just go and buy GMA Garnet, put it in your blast pot and start blasting you are almost guaranteed to fail!

As with most new technologies/products, success in using the product only comes from having experienced consultants assist you and train your teams.

The good news is that Blast-One Consultants spend their life doing this. With over 500 years of collective experience and knowledge gained from being involved in thousands of projects, our Project Consultants can really assist you maximize the profitability on your project when using Australian GMA Garnet. Ask us about how this works.

Blast Nozzle with Garnet spreed

Surface Profile and Cleanliness

Profile Requirement

Many contractors who use coal slag are actually creating too much profile on the steel. Did you know that more coating failures have been attributed to too much profile than not enough? If you are using 20/40 coal slag, you would most likely be achieving a 4-5 mil profile. This is causing the contractor to apply excess primer to cover this excessive profile, costing the contractor more. The below diagram explains how much paint is needed to cover profile:

Different surface profile examples
Watch the video on how to accurately measure blasting profile using testex tape.
Surface Cleanliness

The other advantage of using Blast-One Australian Garnet is that surface cleanliness is greatly enhanced.

Slag blasted steel surfaces inherently have slag particles embedded into the surface at around 500 particles to the square inch. These particles are the result of the sharp slag corners breaking off on impact and impregnating into the steel profile.

Laboratory research has determined that the effect of this extraneous material is detrimental to coating performance. We saw these imbedded particles onsite, protruding right through the paint coating.

No such embedment appears on Garnet blasted surfaces.

Worker Environmental Conditions

Dust Levels when using slag

Slag is quenched from its molten state with cold water giving each particle a brittle structure with distinct fracture lines.

Upon impact with the surface the slag particle breaks down into several pieces. Hence the dust levels are high and the product doesn’t lend towards recycling.

Garnet is an extremely hard stone with low friability, hence a low breakdown rating allowing 10 or more times recyclability. Garnet is very dense with a high specific gravity and any broken down particles fall out of the air immediately.

(We often notice that on slag projects the drift of spent slag and debris travels around 120 feet down wind and only around 40 feet on similar Garnet projects.)

By switching to Blast-One Australian Garnet, you will notice a dramatic difference in dust levels – your workers will go home cleaner and will have much better job satisfaction!

Different dust levels
Different dust levels
Different dust levels
Heavy Metal Content

Garnet as a natural stone has extremely low levels of heavy minerals.

Coal slag is a by-product of the metals refining industry and contains high levels of Toxic Heavy Metals, so much so that many authorities are banning the use of slag purely because of the hazardous nature of the toxins in the virgin slag material. Some states classify slag as a hazardous waste even before it is blasted – the new slag in the bag is hazardous waste! Please be careful when using slag.