What is shot blasting?

What is the shot blasting process?

Shot blasting is widely used in the protective coatings industry as the first stage in the process.

In layman’s terms, it cleans the item that you want to coat.

It can be used on a small scale in an abrasive blast cabinet for small items, however, for most industrial operations abrasive blast systems would be installed in a large purpose-built room with ideally an auto-recovery system to recycle the blast media.

The blasting process is carried out by a trained operator wearing the appropriate PPE. The steel shot or grit used in abrasive blasting is fired out of the blasting gun with compressed air at about 110 PSi, removing any oxidised areas (Rust) and taking the metal back to its original raw state. Because there are small fragments of metal being fired at metal there is a lot of ricocheting in the closed blast room and it is mandatory that the operator is wearing the right protective gear, but also the area is not used for any other process. This abrasive blast cleaning can remove any previous powder coating or protective coatings including old galvanising, although this can be a tricky operation and take considerable time.

When powder coating, we always recommend that you start with grit (shot) blasting, this ensures that we have a clean item to start coating. Then depending on the end product, we might recommend galvanising with Hot Zinc Spray, this applies a thin layer of protective zinc to the item giving it anti-corrosion protection. Then we are ready to apply, either powder coat or wet spray.

What material is used for shot blasting?

All abrasive materials used have their own qualities. The blasting media used should suit the job at hand. In the protective coatings world, we commonly use steel grit, it’s an ununiformed shape for blasting metal to remove any oxidisation, dirt, or old coatings.

Grit blasting is commonly called shot blasting, but steel shot is actually round. At NSP coatings we mainly use grit blasting as our media of choice as it bites better on the metal and removes more of the debris and leaves a surface roughness to specification mark SA2.5 or SA3 for the new layer of the protective coating that follows.

What is shot grit blasting?

Grit blasting, shot blasting and sandblasting are all really the same thing, they are often referred to as sandblasting, but sand is not used anymore because of deadly silicosis.

These are some of the most common media used

Tiny Steel shot
Steel grit
Alumina
Silicon carbide

Is shot blasting dangerous?

The short answer is yes, the shot blasting process is a dangerous operation in untrained hands.

The most obvious is that the force that the shot comes out of the gun could cause significant injury if it came into contact with a body part.

The less obvious is what the blasting is taking off the item, this could include lead paint,

You should ensure that a shot blast machine is only ever operated by a qualified, experienced individual and the relevant protective PPE equipment is used.

The following items should be used:

A filtered air fed helmet
Ear protection
A mask
gloves
Steel toe caps boots

Overview

Abrasive blasting is a very efficient way of removing old coatings or removing rust and other impairments that without removal will result in virtually no adhesion and uneven final coating finish.

We at NSP Coatings will always recommend that the base item is shot blasted, it guarantees that the coating will adhere nicely and the end result of a powder-coated finish or a wet spray finish will look its best.