When a Dubai coating specification says blast cleaning to Sa 2.5 with SSPC AB-1 compliant abrasive, it is protecting the owner from an invisible failure mode: salt contamination under the paint. Here is what the specification really controls, and how to choose garnet that passes.
Why garnet took over from sand and slags
Almandine garnet is a dense, hard natural mineral that cuts fast, breaks down slowly and produces very little dust compared with slag abrasives, with free silica low enough to sidestep the silicosis risk that has banned silica sand blasting in much of the world. Lower dust means better visibility for the blaster, cleaner containment and, on bigger jobs, real recyclability: quality garnet is commonly reused several times in recovery systems.
The two purity numbers in SSPC AB-1
SSPC AB-1 limits water soluble contaminants two ways. Conductivity of the abrasive extract must not exceed 1,000 microsiemens per centimetre tested to ASTM D4940, and the parallel ISO 11126-10 garnet standard caps chlorides at 25 ppm. These limits exist because soluble salts left on blasted steel draw moisture through the coating and start osmotic blistering. Cheap unwashed abrasive fails exactly here, and no primer thickness fixes it afterwards.
What 30/60 mesh gives you
Mesh 30/60 is the general purpose grade for structural steel and tank work. At normal nozzle pressures it produces a surface profile around 70 to 80 microns, in imperial terms roughly 2.8 to 3.2 mils, which sits neatly in the 50 to 85 micron window most epoxy and zinc rich primer data sheets require. Finer grades like 80 mesh suit thin film systems and waterjet cutting; coarser 20/40 digs deeper profiles for thick builds.
Checking a delivery in practice
Ask for the batch test certificate showing conductivity, chloride and sizing. On site, a quick conductivity test on an abrasive sample in demineralised water catches contaminated material before it reaches the steel. Store bags off the ground and sealed; garnet that has sat wet in coastal air can pick up the very salts the specification bans.
MENA Industrial Supplies stocks washed almandine garnet 30/60 mesh in Dubai in 25 kg bags, 1 ton big bags and bulk, meeting SSPC AB-1 requirements with batch certificates supplied. Other gradings are available on request.