Abrasive blast cleaning utilizes a stream of abrasive particles directed onto a metal surface to remove millscale, rust, corrosion products, process scales and foreign particles.

Airborne abrasive is projected through a nozzle and is suitable for open field or on-site conditions, enclosed blasting chambers, and portable enclosed circulating systems.

There are two classes of abrasive, metallic and non-metallic. Practitioners should be aware that a general dust hazard exists for all forms of dry abrasive blast cleaning, and that the use of silica abrasives in dry abrasive blast cleaning represents a specific health hazard to blasters and other people close by. Silica abrasives are banned for dry blasting in Queensland.

The texture and colour of the blasted surface may vary depending upon the type of abrasive and method used. The surface roughness or profile achieved depends on several factors. These include metal substrate, blasting process, abrasive type, abrasive velocity at impact (affected by distance between the workface and nozzle, or wheel), and angle of the blast stream to the workface.

Blast-cleaned surface may start to rust quickly and should always be coated before any discolouration occurs. The use of inhibitors in wet abrasive blast cleaning can maintain the condition of blasted surfaces.

 

ABRASIVE TYPES USED

• Garnet
• Copper Slag
• Ilmenite
• Glass

CLASSES OF SURFACE PREPARATION

Class 1 – Light Blast Cleaning: the blast intensity and distribution are such that loose mill scale, loose rust, and foreign particles are removed.
Class 2 – Medium Blast Cleaning: the blast intensity and distribution are such that mill scale, rust and foreign particles are substantially removed and grey metal is visible.
Class 2.5 – ‘Near White’ Blast Cleaning: the blast intensity and distribution are such that mill scale, rust and foreign particles are removed to the extent that the only traces remain in the form of spots or stripes.
Class 3 – ‘White Metal’ Blast Cleaning – the blast intensity and distribution are such that visible mill scale, visible rust, and visible foreign particles are entirely removed.