Solvent Cleaning – Before any further cleaning or preparation, steel sections are first wiped down with acetone, a thinner, or another type of solvent. This helps remove mill scale, oxides, and some corrosion.
Abrasive Grit Blasting – Grit blasting is the most effective method for removal of particularly difficult dirt, mill scale, rust and old coatings and other impurities. This is achieved using a shot-blasting machine, which the raw steel is passed through.
Prior to blasting, steelwork needs to be cleaned of any oils or grease. It is then blasted with shot or another abrasive material, which bombardes the steel surface, removing any impurities. The machine then brushes off any debris. There are all different types of classifications for blast cleaning a steel section, which will depend on what it is being used for, and what is being done afterwards (such as painting, coating or welding).
Hand & Power Tool Cleaning – Scrapers, wire brushes and other hand held tools are relatively ineffective in removing mill scale or corrosion. However, power tools like rotary brushes, rotary grinders, and needle guns may be useful for cleaning hard-to-reach places where grit blasting is not possible.
Acid Pickling – This involves immersing the steel in a bath of suitable inhibited acids that dissolve or remove the mill scale and rust. This technique is normally only used for structural steel intended for hot-dip galvanising.
Flame Cleaning – This involves passing an oxy/gas flame over the steel surface. The heat causes rust scales to flake off, which can then be removed by scraping and wire brushing followed by dust removal. It is not he most efficient process and is rarely used.
Wet Abrasive Blast Cleaning – As the name implies, this is similar to the girt blasting technique, however, water is employed rather than shot. This contributes to the reduction of a dust hazard, particularly when removing lead-based paints and water-soluble contaminants. Ultra-high pressure water jetting is also used, which is favoured by some because it removes high percentages of soluble salts from the surface.
