Metal structures that are repurposed for use or newly coated always receive a thorough pretreatment. After all, old paint residues, coatings or corrosion must be removed for an optimal effect. The removal of such paint residues can be carried out in various ways. One of the most commonly used methods is grit blasting, also known as sandblasting.
Grit blasting explained
However, the term sandblasting can seem confusing since sand is no longer used as an abrasive or blasting medium in Belgium and the Netherlands. The reason for this is that the quartz that was in the blasting sand disintegrated by blasting into small dust particles that are very harmful to health. Today, therefore, grit is used as an abrasive. Grit are angular particles, often from metal slag, and are considered industry waste. There are different types of grit:
- Sharp-edged single-use grit
- One-time blast media such as olivine sand, garnet and glass beads
- Steel grit: this is reusable and is often used in paint shops
- Steel shot: also used in paint shops and can be used multiple times
Grit blasting works by means of kinetic energy in a blast boiler. Bags of grit are thrown into this boiler, which are projected by a high pressure of compressed air through the blast arm onto a metal structure with an old coating. In this way, the grit pellets scour old paint residue or corrosion off the object and make it rough again. The rough texture is important for putting a new coating on the metal surface. This is because it allows the paint to adhere better and the coating to stay put.
Grit blasting can be performed in various ways. Thus we distinguish:
- machine blasting: normal grit blasting
- vacuum blasting: blasting with a vacuum extraction system to collect the dust from the grit
- recovery blasting: normal blasting with reusable grit or a system to allow grit to be used multiple times
- vaporblasting: combination of rays and water vapor
Difference from other alternatives
We mentioned it briefly at the beginning of this blog, there are different techniques for providing metal structures with the necessary pretreatment for a new coating. For example, besides grit blasting, there is also the previously mentioned vaporblasting, ultra-high pressure water jetting or high pressure water jetting and stripping by induction.
Each technique, of course, has advantages and disadvantages. The big advantage with grit blasting is that it is a dry way of blasting, no water is involved. All coatings, paint residue and corrosion are completely removed and the surface takes on a rougher texture that is optimal for applying new paint or coating. This is less the case with vaporblasting, for example, where the grit grains are encapsulated by the water present.
Safety always a priority
However, the disadvantage of this technique is that it produces a lot of dust and leaves a lot of unusable residue after grit blasting. Because the grit is shot against the metal structure with great force, it pulverizes into dust. Because of this dust production, certain safety measures are required to engage in grit blasting. Performing personnel are always equipped with a safety suit made of thick heavy leather, appropriate protective gloves and a sturdy helmet. At Iris, this safety is always closely monitored.
To avoid everything getting covered in a thick layer of dust and remaining bits of grit flying around during blasting, an enclosure is often placed around the area to be treated. A conditioned space is created, so to speak, in which to gritblast.
An investment for optimal results
Grit blasting may be a touch more expensive than other techniques for removing coatings, corrosion and other paint residues, but it is worth the investment. One square meter of surface requires about 60 to 100 kg of grit, but the extra rough effect left on the structures allows a new coat of paint or coating to adhere better. So it is a very efficient method of providing metal surfaces with the proper pretreatment.
Would you like more information about grit blasting or are you curious about which technique is best for your metal structures? Then contact Iris quickly. We are happy to help you.