Granalha de aço vs. escória

The term slag generally refers to two types of by-product used as an abrasive:

• Metallurgical melting by-products: impurities separated from metals and minerals during melting, welding and other processes (copper, nickel, platinum slag).
• Fused combustion ash: produced by burning coal in high-capacity boilers (coal slag, blast-furnace slag).

Given their varied origin, all slags used in abrasive descaling share the same limitations: they are not recyclable (high abrasive consumption per m²), have very sharp edges and high fragility, which generates abundant dust in the process.

Steel abrasive is produced by melting, with controlled chemical composition. The process yields rounded particles —steel shot— which, when the larger diameters fracture, give rise to steel grit.

In jobs where it replaces slag, sand or aluminum oxide, steel grit is used almost exclusively, sometimes with a small percentage of shot: the angular particle has edges and points and, on impact, works like a tool that bites and tears into the surface. It can be selected to suit the job not only by size —uniform across all particles— but also by hardness, within defined ranges.

Its great advantage is recyclability: depending on diameter, type and hardness, a single charge is projected between 700 and 5,000 times —versus slag, which is single-use. Being quenched-and-tempered steel, it does not contaminate the work surface. As it does not absorb moisture, it needs no prior drying, and its uniform grain size produces a completely even finish.

O contraste é enorme: para o mesmo trabalho, a granalha consome 5 kg frente a 370–570 kg de escória —entre 74 e 114 vezes mais— porque a granalha é reciclada centenas de vezes e a escória é de uso único. Além disso, limpa entre 40 % e 65 % mais rápido (20 vs. 12–14 m²/h) e gera muito menos pó.