What surface prep level is typically required for steel to receive spray-applied fireproofing?

• A. A blast-cleaned surface to roughness level SA 2.5 per ISO 8501-1
• B. Roughened to SA 1.0 per ISO 8501-1
• C. Painted surface
• D. Dusty, oily surface

Answer: (D)

The key idea is that spray-applied fireproofing needs a clean, dry, and highly adherent steel surface. Standards like ISO 8501-1 describe surface cleanliness levels, and for critical bonding of fireproofing, the most reliable prep is blast cleaning to a near-white metal level (SA 2.5). This treatment removes oil, grease, dirt, rust, and loose coatings, leaving a smooth, clean surface that provides good mechanical bonding for the fireproofing material. A roughened level of SA 1.0 is less thorough and may leave contaminants that can weaken adhesion. A painted surface would require removal of the paint to expose bare steel, and a dusty, oily surface would not meet the cleanliness needed for proper bonding. So, blast-cleaned to SA 2.5 is typically the correct prep for reliable spray-applied fireproofing adhesion.