A Brief Rundown of Abrasive Blasting and
Protective Coatings Services Corrosion Protection
Exposing metal to water and oxygen will trigger a chemical reaction commonly known as corrosion, producing a new material such as rust.
This residue can continue to react with water and oxygen, spreading corrosion in healthy material.
Early detection, removal through blasting with various types of grit and the restoration of protective coatings are essential to stop active corrosion and prevent further deterioration.
Sandblasting and Grit Blasting
- Involves the forceful application of a stream of abrasive particles onto a metal surface, removing mill scale, rust, corrosion products, process scales and foreign particles.
- It can be used to clean, smoothen or roughen a surface before applying protective coatings.
Types of abrasives
- Metallic abrasives include steel shot, steel grit, stainless steel shot, cut wire, copper shot, aluminum shot, and zinc shot. They withstand repeated impact and suit cleaning processes which reuse abrasive materials.
- Non-metallic abrasives which are inexpensive, include silica sand, garnet, walnut shells, copper refinery slag, coal furnace slag and iron furnace slag.
Abrasive materials used in dry blast cleaning are general dust hazards.
Silica abrasives pose serious risk because they break up easily and produce large quantities of dust that could lead silicosis, a debilitating lung disease.
Silica is not an option in certain parts of Australia where its use in dry blasting is prohibited.
Classes of Surface Preparation
- Class 1 Light Blast Cleaning removes loose mill scale, rust and foreign matter.
- Class 2 Medium Blast Cleaning removes substantial mill scale, rust and foreign matter from the surface, revealing grey metal.
- Class 2.5 Near White Blast Cleaning removes all visible residues such as oil, grease, dirt, mill scale, rust, corrosion products, oxides, paint or other foreign particles on at least 95% of the surface, leaving very light shadows, streaks or discolourations. This method is ideal for plant facility maintenance work.
- Class 3 White Metal Blast Cleaning is the ultimate corrosion removal method which removes all mill scale, rust and foreign matter, revealing a uniform metallic white or grey colour. It promotes maximum performance of protective coatings, ideal for materials exposed to exceptionally severe conditions such as the constant immersion in water or liquid chemicals.
Outcomes of blasting with abrasive media will vary according to the type of abrasive, metal substrate, blasting method, abrasive velocity at impact, and the angle of the blast stream to the blasted surface.