Every marine coating specification quotes a blast grade, and every coating failure investigation starts by asking whether it was achieved. The grades come from ISO 8501-1, which defines them by photographs of prepared steel.
The grades in plain language
Sa 1 is a light sweep that removes loose scale and paint only. Sa 2 removes most mill scale and rust but shading remains. Sa 2.5, called near white metal, is the workhorse grade: at least 95 percent of each square of surface free of visible contamination, with only light staining permitted. Sa 3 is white metal, visually clean steel, rarely specified outside aggressive immersion service because holding it in humid air is difficult.
Why marine work standardises on Sa 2.5
Epoxy hull primers and tank coatings are specified over Sa 2.5 because their adhesion and immersion performance are tested at that grade. In Gulf humidity, blasted steel begins to gingerbread within hours, so yards blast and prime in sections the same day.
Abrasive choice sets the profile
The blast grade describes cleanliness; the abrasive sets the anchor profile. Copper slag is the economical single use choice across UAE yards, while garnet cuts faster with less dust and can be recycled in contained setups. High build coatings typically want 50 to 85 microns of angular profile; confirm the range on the coating data sheet.
MENA Industrial Supplies stocks both abrasives and the primers that go over them, quoted same day from Dubai. See the full marine range on our marine paint supplier page.