
Abrasive blasting for pre-coating surface preparation
Effective Abrasive Blasting, Improved Surface Preparation
Informed abrasive media selection and process execution determine the success of abrasive blasting, which is a critical process prior to surface coating in corrosion protection.
Surface coating is one of the extensively utilised tried and tested techniques of corrosion protection of steel and other metals used in harsh industrial environments to preserve structural integrity and extend their life spans. However, for one thing – coating is as effective as the cleanliness of the surface where the coat is to be applied. Thus, it is essential that the process of surface preparation, a critical process prior to coating, is thorough.
In present times, industries, owing to advances in research and development, have different techniques at their disposal that can be used to undertake the process of surface preparation. One of the techniques that are being used extensively is abrasive blasting. Abrasive blasting involves thrusting an abrasive medium at ultra-high pressure against a surface. Compressed air powers the blasting nozzles. Dirt, debris, rust and other unwanted marks are removed from the surface while preserving the integrity of the underlying material.
Usually, the following are some of the materials are used to perform abrasive blasting: Sand, Steel shot or grit, Glass bead or crushed glass, Aluminum oxide, Silicon carbide, Coconut or walnut shell, Copper slag, and Plastic. Abrasive blasting is considered an alternative to chemical cleaning. This is due to the versatility of its application and benefits. Of course, this depends on the nature of the material used and if it is deployed in a recommended application.
Host of applications
Due to its comparative advantages over chemical cleaning, it is not surprising that abrasive cleaning is widely used in a host of applications, just to single out a few:
- Surface preparation prior to coating, painting or bonding
- Removing rust, scale or existing coatings
- Removing burrs or edge profiling on machined components
- Finishing of precision parts
Guaranteed benefits
Based on information gathered from a survey sent to ten leading providers of abrasive blasting solutions to mining, oil and gas and petrochemical projects, there are several guaranteed benefits of using the technique. The common ones are:
- Eco-friendliness: Generally, abrasive blasting is regarded as environmentally friendly due to the properties of the materials. The materials do not produce greenhouse gases during blasting.
- Efficiency: Abrasive blasting is more thorough while preserving the integrity of the underlying surface. It gets into nooks and crannies that otherwise would not be possible with other surface cleaning techniques. This guarantees efficiency.
- Control over surface profile: Abrasive blasting gives control of surface profile or level of roughness. This can be achieved by using different particle sizes of blasting medium for the surface preparation process. This is virtually impossible with chemical cleaning.
- Safety: Abrasive cleaning is regarded as a safer option than chemical cleaning methods. Some chemicals may have carcinogenic properties and cause lung disease and cancer, besides being flammable. On the other hand, abrasive media are considered a convenient alternative to chemical cleaning. Mainly, this is due to their inertness, as they do not react chemically with the material that is being cleaned. On the contrary, chemical cleaners react and cause damage to the underlying material.
However, it has to be acknowledged that sandblasting poses a health risk to the operator. That is why legislation obligates organisations to ensure that their employees are fully protected from exposure to fine dust and sand particles.
Abrasive media
Abrasive media have different properties, including hardness, strength, density, and shape. Typically, they are available in a range of particle sizes to suit the surface finish required. Increasingly, there is material that can be recycled and reused many times, as well as less harmful.
Product selection and execution
Generally, informed product selection and process execution determine the success of abrasive blasting. More often than not, failure of abrasive blasting is always down to the missteps in the application of these two steps. Poor coating exposes the surface to corrosion. Imagine a situation where the surface has to be restriped and the process repeated. It is very costly to undertake. Surely, there is no alternative better than an informed choice in abrasive blasting.
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Selecting the right abrasive
BLASTRITE is South Africa’s largest manufacturer and distributor of granular abrasives to the surface preparation industry and offers a range of abrasives to suit the various surface preparation applications in the corrosion control process.
There are several factors to consider when selecting an abrasive for a blasting application, and Blastrite can assist with both the abrasives and the technical expertise in this regard. When selecting an abrasive, consideration should be given to the following:
- Is this a once-off or on-site blasting project where a disposable product should be used, or is there a recovery system where a recyclable abrasive should be used?
- What is the substrate that is to be blasted? Blastrite supplies abrasives for ferrous and non-ferrous substrates.
- What is the current condition of the substrate? Is there an existing coating to be removed, is there heavy rust, or mill scale present?
- What is the desired condition of the substrate after blasting? In most instances abrasive blasting is done to create a profile (roughened surface) prior to a coating to create a key for the coating to adhere to.
Other applications require a rubber lining to be removed, a surface to be peened, polished, or there is a desire for a certain aesthetic appearance to the surface.
Blastrite can assist with recommendations on the correct size, shape and type of abrasive. In all above examples products such as Blastrite® Platinum Grit, Microblast® Garnet, Steel Grit, Steel Shot, Glass Grit, Glass Beads and Aluminium Oxide can be used to achieve the desired results.
Blastrite is a manufacturer and distributor of granular abrasives commodities. To this end, we have two mineral processing facilities in South Africa as well as sales and distribution infrastructures in Cape Town, Durban, Richard’s Bay and Johannesburg as well as distributors in Pretoria and Port Elizabeth all of which supply the shipping, construction, mining industries.